The Mystery Crash, by Van Powell: a Project Gutenberg eBook

Bob Wright pointed from the cabin window of the monoplane. Al, his younger brother, peered toward the ground.

To make himself understood above the roar of the engine, Bob put his lips close to Al’s ear while Curt, Bob’s closest friend, also a passenger, bent close to catch his words.

“It’s a mystery all right—but you can’t see from here. It was in that cornfield we passed over.”

“Why did you say ‘our’ mystery?” Al asked at the same instant. Bob answered both at once.

“The mystery is: Why is an airplane hidden in the grove at the edge of a cornfield? Our mystery because we discovered it and because, ever since we helped father solve his detective cases and took an interest in aviation we have wanted to solve something that connects up puzzles and ’planes!”

“A ‘crate’?” Al stared out. “I don’t see it.” Bob was not there to reply. He moved up to the pilot, Langley Wright, his cousin, who was test pilot for the Tredway Aircraft Corporation and who was giving this beautiful “job” its final test and check flight.

“Lang,” he said, “I saw an airplane in the grove at the edge of that last field we crossed. Circle back, won’t you?” As Lang turned from jotting down some data, Bob added: “The ship hasn’t crashed. It’s in among the trees—backed in. I caught a glimpse of it, and then the trees hid it. I’d like to have another look.”

Lang, twenty-one and an expert flyer, grinned at his sixteen-year-old cousin, dipped ailerons, kicked rudder and with a good “bank” as the craft swung its nose around, he deftly counteracted a tendency of the ship to go into a sideslip, jotted down some information on his data board and then looked out of his window.

“That’s why I told Al and Curt it’s a mystery,” Bob replied. “The ship has been hidden! Its tail is in between trees, and the wings are under trees with high branches. I don’t believe it could be seen from the highway that runs by the field. I know it wouldn’t be noticed from the air, except by chance.”

“Hm-m-m!” grunted Langley, “I’ve heard of hidden treasure, but this is the first hidden ’plane——”

“I see it!” Lang continued to circle, in order to get another sight of the mysteriously hidden ship. As they came around again Al and Curt located it also.

“It’s staked down!” Al, although he was the youngest, not much past thirteen, had the quickest eyes of the group. “I saw the stakes, and rope over the wing-tips.”

They saw nothing more, however, and after Lang had refused Al’s impulsive request to “set down” in the small field, the party flew on to the landing field of the Aircraft Corporation where Lang had some alterations to report in the adjustment of the ship’s balance before it could be delivered to its purchaser.

“Let’s get our bicycles and ride out to the field,” urged Al, as the trio of comrades alighted beyond the aircraft plant.

“I was right,” commented Bob, as they left the wheels beside the highway and climbed over the high rail fence enclosing the stubble where corn had recently been cut down. “You can’t see the airplane from any place along the highway——”

“I can see from here it hasn’t cracked up,” Curt declared. “Not a scratch on it and the landing gear is perfect.”

“Whoever flew it must be clever,” declared Bob. “Look at the narrow strip of open, smooth ground he had to ‘set down’ on. If he hadn’t been able to shoot the field so as to get in on that long, smooth side, with only a few feet clearance, he’d have come down in rough stubble.”

“Yes, he must have been good,” agreed Al. “And it proves that he was forced down. Any sane pilot would have gone on to a better spot.”

They reached the airplane, a two-winged model with a radial motor and small wings; it was a speed ship, trim and mystifying with its dark, brown body and airfoils freshly done.

Curtis, whose age was midway between Al’s thirteen and Bob’s sixteen, clambered onto a landing wheel and observed the instruments on the dash. “Plenty of gas, and oil,” he remarked. Then his companions saw his face change.

“Look!” As he called he leaped from his perch so that Bob could occupy it; Al was up on the other side, and it took no explaining to show what had caused Curt’s exclamation. Both youths saw the small square of paper pinned to the folded parachute on the seat.

“‘I can read it from here,” Al said, and reported. “It says, ‘Everything O.K.’”

“Crickety Christmas!” Curt resorted to his favorite expression. “‘Everything O.K.’ Then it wasn’t a forced landing.”

“No,” agreed Bob. “It didn’t seem like one, somehow. The ship is too carefully tucked away. And, now—this note. Who is it to? Who put it there? Does it mean the ship is all right—or something else? I was right when I said—‘there’s our mystery.’”

“But what can we do about it?” objected Al. “Take turns watching? Wait to see who comes back, and what he does?”

“I think not,” counseled Curt. “It may be a mystery why the crate is here, and all that! But it isn’t any of our business—is it?”

“No,” admitted Bob. “Let’s go home, and see what father thinks of it. There is probably some easy explanation we haven’t thought of.”

They could not consult the private detective whose success had been so pronounced that cases came to him from distant cities: he was out of town that night.

When they rode out to the field the next day, at sunrise, looking for the mysteriously deserted airplane it was gone!

“Where is your mystery now?” Curt was inclined to poke a little fun at Bob. “As the sleight-of-hand performers say, ‘Now you see it, now you don’t!’”

“Anyway,” Al who was poking about in the grass under the trees, bent and then exhibited a damp, crumpled paper, “here is the note. Now, what do you say if we have a session of the old Master Sleuths, and see what we can deduce from this paper?”

A year before, asked to do a little investigating for Mr. Wright, when he was handling a case where youths would be least likely to arouse suspicion by shadowing, the trio had become intensely interested in detective work and had termed themselves the Master Sleuths, more in fun than in earnest. However, when they had become “air minded” the term had been dropped. Al, reviving it, won a grin from Bob.

“All right,” Bob agreed. “The paper is damp. It has been out in the dew. Under the trees it would take a good while for it to get as soggy as it is. The writing has smudged—it’s sort of purple——”

“Then all we have to do is to find a man with an—” Al was not allowed to finish. Bob broke in, as older brothers like to do.

“Yes—get ‘the man in the gray suit!’ How many indelible pencils do you suppose there are in this country?”

“All right!” Al took the matter good-humoredly. “Anyhow, if a man wrote it and a man read it and threw it away—two hands have handled it.” He put it carefully in his pocket. “There may be fingerprints.”

CHAPTER II
AT ROCKY LAKE

“I hear it!” exclaimed Al. He ran out onto the turf that had been used as a runway, probably, when the airplane took off.

Bob, craning his neck, staring up toward the great banks of clouds which the early sun was painting with rosy fire, looked puzzled.

“Easy! Lang came home a little before daybreak. He had been at the airplane plant all night, with the ‘mechs’ because Mr. Tredway wanted to get that Silver Flash ready for delivery in a rush. I didn’t go to sleep again. I got up, and dressed and went out to tighten the handlebar on my bicycle. I glanced up, just as day broke, at the little windsock I have on our roof.”

“I don’t see—” began Al; but Curt, wetting the back of his hand, tested the air in various directions.

“You use your head, Bob,” he said admiringly. “The breeze is pretty strong, and it has shifted around to South , straight from the Equator.”

“I thought you wanted to be a Master Sleuth, last year,” remarked Curt. “Use your eyes and your brains.”

“Um-m-m—the airplane must be gone a long time because the wind was West and now it’s South—um-m-m. Oh!”

“‘Ah-ha!’ cried Shawkhaw,” Bob mocked, twisting the famous Hawkshaw title as he made fun of his brother.

“This turf runs East and West.” Al ignored Bob’s mockery. “That biplane was a speed model and it would have to get up higher speed than the average to take off. The runway is too short to give it a good run, so it couldn’t very well have hopped off in time to get over the trees unless it took full advantage of the wind! Isn’t that it, Bob?”

“That’s it. The wind changed about the time we left our meeting point with Curt. So that airplane ought to be well on its way, wherever its way leads.”

“There it is!” cried Al, pointing toward the South. “It’s only a speck. But you see it, don’t you, Curt?”

“And it isn’t the biplane we saw here, at all,” Bob said. “Curt, do you know what?——”

“Yes. It’s the very ’plane we were in yesterday, with Lang. He gave it a final check-up and said if they worked on it all night it would be ready to take off today. That’s it, all righty! The biplane was brown, and——”

“This is the Silver Flash! I can see it glisten against that dark cloud,” added Al. “I think it’s coming down.”

“Come on!” urged Al, scrambling over the short stubble in the field, in haste to reach his bicycle and pedal toward the picnic grounds, less than a quarter of a mile away, in which Rocky Lake was situated.

“No! Come on!” Curt agreed with Al. The airplane was out of control. It was diving, straight toward the amusement ground around the lake. “It’s a crack-up!”

Behind the trees, out of sight, like a silver streak, a comet, the airplane fell. Three hearts went cold as the ship was lost to view behind the foliage. While they could not see the craft strike, any spot in Rocky Lake Park was bad for a landing: dense trees, whole groves, alternated with stands, pavilions, and the deep, boulder-studded water of Rocky Lake and the rivulet which fed it.

Three minds worked as one, three pairs of legs tumbled their owners over the stile, onto the roadside turf, up to the bicycles.

Pedaling like madmen they made short time of the trip to the edge of the amusement spot.

“I think it was directly over Rocky Lake!” Curt, in the lead, called over his shoulder.

Dropping their wheels by the roadside they ran, winded but determined, towards the picnic grounds.

“It’s half buried in the water.” Al puffed along a little to the rear. “I hope the pilot——”

“No!” Bob responded to Curt’s question. “It must have been some other pilot—I can’t think who, though.”

“Hurry!” urged Al. “Hello—hello!” he called, passing the pavilions. “Is anybody around! Wake up—somebody! Help! Help! A ’plane has cracked up in Rocky Lake!”

“See anything of the pilot?” Bob turned to Curt. Gasping for breath they had reached the shore of the lake, by a small wharf where rowboats were hired during the day.

Quite near the shore, and on the rocks, with one crumpled wing, and with her nose and cabin buried in soft, oozey mud, the smashed monoplane lay with its pitifully useless tail assembly sticking up into the air. The “flippers” had carried way with the impact and hung by the control cables.

“I hope—I wonder”— He could not finish. The thought flitted through his mind that unless the pilot had been extremely quick and very clever, he could not have gotten out of the cabin—in time. The falling craft had been close enough so that had any figure leaped, especially with a parachute, they should have seen it clearly.

“Al,” called Curt, “stop calling for help! There isn’t anybody here. Run to the farmhouse across the road—no, that’s empty. Ride back down the road, till you see an automobile and send it to town for help. If you don’t meet one, stop at the first house and telephone.”

Al, for all his natural eagerness to be at the scene, to share in their experiences, saluted without a word of remonstrance and hurried away. Meanwhile Bob, realizing that the oars for the boats were locked in the small pavilion on the wharf, determined to break in, feeling that the emergency removed any taint of robbery or pillage from the act.

Fortunately he found the old, rusted lock not caught. He slipped the rusty padlock, slipped the hasp free, and ran back to the dock where Curt had a boat untied and ready. In this, pushing off, they rowed out to the airplane. The weight of its engine was very slowly driving its nose deeper into the soft ooze of the marshy ground at that end of the lake.

“What’s the matter?” cried Curt, and as he saw the expression of Bob’s face he, too, became intent.

“There it is again!” panted Bob. “A call—a call for help?” he questioned.

CHAPTER III
A GREATER MYSTERY

Bob sent the boat through the mirrorlike water. He headed for the immersed nose of the airplane and as they rounded the cabin, part of it sticking up forlornly, Curt lifted a hand to point.

“It looks as though the pilot tried to get out of the cabin, and either pulled his ripcord too soon, or else some part of the harness caught and held him—until too late!”

Sobered and worried, wondering just what to do and who had called, they sent their eyes questing here and there—into as much of the cabin as they could see from the window just under the transparent surface of Rocky Lake, but without result.

“I thought he might be caught in the cabin,” said Bob. “But I can’t see any——”

Bob pushed away from the fuselage of the sinking craft, and with a sweep brought the bow of their boat around.

“Oh!” he caught sight of a head bobbing in the water, “oh, Curt—I’m so glad!”

“Probably he slashed it off. Maybe he saw it was too late to get out, that the ’chute was too low, and he slashed himself free and started to swim across the water——”

“We thought we did,” Bob called back, and, as they came closer the man spoke less loudly.

“He can’t be!” Curt commented when the man failed to reply, being busy clearing water from his eyes to look around the lake again.

“Haven’t seen anybody at all,” the man spoke as he caught the gunwale and pulled himself up and into the boat with Curt’s aid. “Heard a shout, though. Row back boys, to that thing.”

They went back over the course. The stranger, studying the aircraft, seemed very much disturbed and worried. He had a hand ready to catch the struts of a wing as they swung under the tilted airfoil: while Bob stowed the needless oar on that side he drew the boat forward.

“Untie that painter,” the stranger ordered. “I’m going down under the nose, and the mud might hold me—so, if I signal, you pull.” As Curt unknotted the tying rope and threw it to him, the man looped an end under his arms, knotting it swiftly, flung the short coil to Bob and lowered himself, disappearing into the water, his descent stirred up mud, moiling the water. Down he went, hidden almost at once in the murky disturbance.

Paying out the rope until it grew slack, Bob took a turn around a rowlock, and they waited breathlessly. Some bubbles floated up and broke. Then came a tug on the rope.

Curt, who had already come to the midships section, helped Bob tug and haul in the wet manilla strands. The stranger came up through the murky water, emerged, shook himself free of the liquid, caught the boat and shook his head.

“Not in the cabin—only thing I can think of is—if he tried to jump and got under the thing.”

People were arriving on the bank, shouting to one another, calling for information, shipping oars in boats. Al, having met several motorists, had spread the alarm, and then had ridden on to telephone the police and to report the crash.

Al, having returned, was in the second boat to arrive by the slowly sinking craft.

Bob gave him a concise report while they pushed away from the place to enable a deputy sheriff to take command and to jot down the stranger’s explanation and their own, from Curt.

“I wish you boys would row me across the little bayou, here,” the man said. Al had transferred to their boat by that time.

“Take me to that point, over there,” the man added. “It’s closest to where I dropped my motorcycle when I saw the thing happen.”

Bob nodded. The presence of the motorcycle beyond the lake, where it was nearest to the road, explained why they had seen the man swimming toward them. He must have heard and seen the airplane, watched its descent, and then rushed to see what he could do.

“No,” he replied. “If they do, they can find me soon enough. I’m off to get into dry duds. I didn’t waste time riding around the end of the lake. I dropped my motorcycle and ran in to see what I could see.” He smiled, sadly. “I guess I was too late, even at that.”

Thanking them as he climbed onto the rocky shore, he pushed the bow of their boat into the stream again, and watched them turn in the still water.

“You can tell the police I didn’t think they’d need me right away,” he called. “I’m passing through this section, and I don’t want to be held up and kept here for any sort of investigation. You saw as much as I did. Well—goodbye!”

He turned, and as they heard the “crash ’bus” arriving from the airport in a nearby city of which they lived in the suburbs, Bob rowed his two young companions back toward the airplane.

Preparations were made to drag under the craft, and to lift it, if tackle could be gotten into suitable position, to see if any trace of the missing pilot could be discovered.

Nothing further developed, however, and one of the “mechs” with the airport ’bus told Bob it would be afternoon before they got the monoplane out. The three comrades had given the police lieutenant all the information they could. There was a healthy appetite making itself felt among them.

“Wait, all of you,” urged the reporter for a small suburban daily. “I’ll make heroes of you yet.”

Protesting that they had done nothing heroic and that they did not want to be “put in the paper” for doing their duty, Curt and Bob refused to answer any questions. The police, Bob said, might not want information published. He did not know, but he would prefer not to talk. “Oh, I see—there is a mystery, then!” the reporter declared. “Well, if you won’t talk—” he began to write swiftly.

“If we won’t talk,” Bob commented as the trio walked toward their bicycles. “He’ll write something anyhow.”

“It’s queer that there isn’t any trace of the pilot.” Al’s mind returned to the tragic part of the crash.

“Maybe he jumped clear, got away and went into the water, and then, coming up, got to land. He may be on shore, somewhere, hurt, or too weak to make himself known.”

“Let’s hope it’s that way,” said Bob. “Well, we’ve got a long road to breakfast. Mother will be just about wild. I left a note, but she will worry about Al and me, just the same. If we go to the ball park and don’t get home within half an hour after the game, she frets.”

“Excuse me, boys.” A pleasant voice behind them caused the three to wheel around. They saw a pleasant-faced man, beside an automobile, parked close to the bicycles they were disentangling. “If you want to get home in a hurry, pile the bicycles in that little comfort station over there, and tell the attendant ‘Barney’ said to look out for them. I’m from the aircraft plant, and as long as I can’t do anything here, if you’ll hop into my car I’ll ride you home while you give me the facts as well as you know them about this smash. It’s a bad thing, and I want to get as straight as I can what happened.”

They were very grateful to Barney, who neglected to furnish any other name. He waited until they had stowed away the bicycles, and while he drove them toward the village he questioned them rapidly.

“I think you are all very brave, and quick, and fine,” he commented, after they had, in turn, recited their adventures. “You acted splendidly and I thank you very much.”

“We did our duty,” he replied. “But why are you thanking us? I know it was one of the Tredway airplanes because we were in it, with Lang, yesterday on check-up. But who was in it, and what do you think happened—really?”

“The owner of the manufacturing plant was in it,” said Barney, very soberly and sadly. “Mr. Tredway was flying it himself. He wanted to deliver it in person—for a reason.”

“Yes,” said Barney. “There is a mystery behind that crack-up—it’s more likely it’s a ‘washout.’ Anyhow, there is something behind the smash, and—I’ve heard there is a private detective, a Mr. Wright, at Forty-one Elm. If you can tell me the quickest way to get there, I’ll appreciate it. I want to consult him—on this case.”

They directed him, and eventually he drew up the car before the neat, cozy cottage. Curtis, accepting the invitation to stay for their somewhat belated breakfast, sat, with Bob and Al, in the cheerful breakfast room, finishing up a stack of pancakes thickly syruped, when Bob was sent for.

Returning, after a few minutes, he showed his younger brother and his best friend a face of elation.

“There is a mystery, all righty,” he declared. “And you’re to come with me——”

“Because,” retorted Bob, “we’re—in—on—it!” As the others jumped up he added, “Father’s home and he’s taken a real air mystery case!”

CHAPTER IV
THE SKY SQUAD IS FORMED

Entering Mr. Wright’s library, which the detective used as a reception room for clients, Bob, Curtis and Al could hardly repress their excitement. To share in the possible solution of a real mystery of the airlanes was more than they had really dared to hope for.

Seated opposite Mr. Wright, smiling pleasantly, was the man who had given no other name than Barney.

“Good morning, Mr. Wright.” Curtis Brown greeted the quiet, but cordial father of his two chums. Al added a salute to his father.

“Sit down,” suggested the detective. Bob, Curt and Al ranged themselves along the leather upholstered davenport at the side, where the light was on their faces. Mr. Wright had his room so arranged that only his own place beside the desk enabled him to keep his face in the shadow; clients and other visitors had to show every expression in the light from the two sunny windows.

While Mr. Wright seemed to be deciding how to disclose his plans, Curt compared the two men.

They were of very distinct types. Fred Wright would make anybody think of an ordinary, everyday business man, fairly prosperous, quiet in his manner, affable and cordial in his speech. His calm, serious face was neither severe nor too soft; and while its steel-gray eyes were kindly, they could look through a person, it seemed, and find out, almost, what that one was thinking, or, perhaps, trying to conceal.

Barney, on the other hand, made one think of a working man who had risen to a position of prosperity and influence without being able entirely to shake off his servile, unpolished manner. Although his clothes were expertly tailored, he seemed a little ill at ease in them. What was more, he gave the impression that he knew it!

He was a trifle blustery to cover his feeling of inferiority, Curt decided; and he had a habit of interrupting when another person was speaking. However, this might be due to excitement, Curt thought charitably.

Glancing sidewise, he sensed that much the same comparisons were passing through Bob’s mind. Al gave no thought to character. His whole attention was bent on the possibility of “action!”

Curt, who liked to look for good points more than for the other sort, checked up Barney’s dark eyes, almost black, and decided that they were only serious because of the gravity of the situation. They could twinkle with fun, he guessed; also, the mouth was so shaped that Bob admitted to himself that Barney smiled oftener than he scowled.

“I have told Mr. Horton about you three young aviation enthusiasts,” Fred Wright began. “Also I have explained that you used to be very fond of ‘detecting’ in a decidedly amateurish way, of course.” He smiled across the desk toward Barney, whose face broke into a broad, pleased grin, immediately suppressed because of the seriousness of his errand.

“If you say so, sir. Well, Barney, then! We were crazy to be great detectives, because father is one,” he paid the compliment whole-heartedly and only his father smiled and shook his head deprecatingly, “but we let our enthusiasm take the place of brains,” Bob added. “I was not much help because I let vanity get the best of cool, common sense——”

“I was so short-sighted, in my mind, that I forgot to look at the whole of a case and pinned my nose down onto every little clew,” Curt grinned sheepishly, “so I kept going around in circles.”

“All the same,” Mr. Wright looked over at Barney, “in such work as boys could do—they were a few years younger then—these three helped me a great deal in handling two quite important cases.”

“However,” the detective continued, “they turned from being Master Sleuths, as they termed themselves, to aviation——”

“But we didn’t give up wanting to be detectives, really!” exclaimed Al, earnestly. “We were looking for a way to mix the aviation with the detecting—only we haven’t gotten into either one.”

“Barney has brought me a very baffling case,” Mr. Wright explained. “Unfortunately, I am so deeply involved in another matter that I cannot drop it.”

“Not personally. That is, I shan’t be able to investigate in person,” the detective replied. “That is where our three assistants will figure——”

“And be Airboys and Master Sleuths, both at the one time,” Barney interrupted.

“Hooray!” Al clapped his hand to his knee, unable to restrain his enthusiasm. Mr. Wright, although with a tolerant, if brief smile, shook his head at his younger son.

“How can we combine aviation and detective work?” asked Curt, the most practical of the chums.

“By going to the aircraft plant to work as mechanics’ helpers, or whatever positions Barney sees fit to put you in,” Mr. Wright told them. “That takes care of the detective work because you will have to keep eyes and ears open and without appearing to do so.”

“That takes no effort at all,” agreed Al. His father, knowing Al’s expressive face to be easily read, made no comment.

“While you are at the aircraft plant,” Barney took up the explanation, “you will be working in and around the crates we are building, and you will learn a whole lot about how an airplane is put together, what the parts are for, and how they are assembled. That’s the aviation part.” He emphasized the first syllable, making it “av-iation.” “What do you say?”

“Of course we will be glad to learn.” Curt was more sober. “That ought to be one of the first things for anybody to do who means to be a pilot.” Mr. Wright nodded and Curt proceeded. “A good grounding in airplane construction will be fine. But—for the detective part—I think we ought to be very serious and consider it carefully.”

“Indeed you should,” agreed Mr. Wright. “There is a deeper mystery to be solved than appears on the surface.”

“I see that,” agreed Curt. “And we must be sure that we will be a help and not a hindrance to you——”

“Oh, we won’t be a hindrance!” Al was almost bouncing on the divan springs in his eagerness. “We’ll watch, and catch whoever you want caught—maybe learn to fly a ‘crate’ and hop off and fly after him and ride him down and force him to land—and there you are!”

All the party laughed. Al, realizing his childish lapse into silly chatter, laughed, finally, himself, a little ruefully.

“I see what Curt meant, now,” he said, more quietly; but his excitement was hard to hold. “But, anyhow, Mr.——”

“Anyhow, Barney, we will try to help. We can learn about airplane construction, and that will be fine; but we will give all our minds to watching and listening and doing whatever is wanted of us—we ought to form some kind of club or order, so we would have a head to get orders from father—especially if he is too busy to take part himself.”

“That’s sensible, even if it does seem boy-like to want to have a secret association,” said the older detective.

“I think the game is more important than the name,” observed the older detective.

“Oh—but with a good name for our band, and a chief, we can know where we are,” urged Al.

“All right,” said Curt. “Let’s humor the youngster!” Al grimaced at him, but subsided as Curt went on. “We are detectives as well as airplane enthusiasts. Why not combine the two in the name of the order we are to form—something about the sky, and something about a police—detective squad——”

“Crickety Christmas!” Curt was as enthusiastic as Bob and Al became on hearing the words. “That’s it!”

“Very well,” Mr. Wright was patient, but a little annoyed. “That being settled, we can take up the important matter of—the case!”

CHAPTER V
A DOUBLE PUZZLE

“I wish we didn’t have to waste the time,” he objected. “I’ve went through it all with you, Mr. Wright, and I wanted to take these lads along back to the plant in my car. I wanted to make it look like I just happened on them at the accident—the—well, the accident, and found they were interested in av-iation and brought them back to fill a couple of places in the plant.”

“But how can we solve a case if we don’t know what it is?” remonstrated Bob.

“As a matter of fact,” Barney turned to Bob, “I think you would do a whole heap better if you went in to it blind, sort of. If you know all about it, you’ll go out to the plant, all serious and acting like judges or detectives. If you take it the way our youngest friend, Al, does—as a sort of lark—you won’t be suspected so quick.”

“There is something in that,” Mr. Wright admitted. “Al’s face is apt to give him away if he thinks it is really serious. Perhaps——”

“But all the same, Father,” Bob declared, “how will we know what to watch for? How will we know what to report?”

“Watch anything you see. Listen to whatever you hear. Report the whole business!” Barney exclaimed.

“That does seem wise,” Mr. Wright agreed, rising also. “Boys, let’s emphasize the Sky part of your order, and let the Squad side rest awhile. Barney wants to get back to the plant—he is the Manager, I meant to explain. He ought to be at the end of a telephone wire. Let’s say only this: There is a double mystery. First of all, valuable parts have been missed, from time to time, from the plant. That is a minor matter, at present, but your first puzzle is—where have the missing parts gone and who took them? But, as I said, that is a minor affair, because——”

“Somebody has tampered with some of the finished crates,” broke in Barney. “Why, and who—that’s the second puzzle!”

“Suppose you take that as enough for the present,” suggested Mr. Wright. He turned to Barney. “Now these three young lads are alert, obedient, and they will follow instructions to the letter, if you give orders,” he explained. “You have already seen how——”

“How quick they are in emergencies! Yes sirree! All right. I know I can depend on them. Sorry you can’t investigate in person, Mr. Wright—but maybe this way will work out best. Anyhow, nobody at the plant will get suspicious of these boys. They won’t have the brains of older men, like you and me, but they will have quick eyes and wide ears,” he laughed, and beckoned, “come on, lads.”

A little disappointed, feeling that there was more behind the mystery than Mr. Wright had disclosed, but accepting his “lead,” Bob, Al and Curt caught up their caps from the hall rack and followed Barney into the car.

As he drove toward the large manufacturing buildings, the administration offices and the assembling rooms, “dope” rooms and testing field that formed the Tredway Aircraft Corporation plant, Barney kept away from talk about the mysteries.

Instead, he questioned them about the plan for their new organization, suggested secret codes, urged them to elect a “Boss Pilot” and really fired their imaginations to such a point that when they came in sight of the aircraft plant they had almost forgotten their disappointment at not being taken fully into his confidence.

“Well,” he said, when they turned in at the gateway in the high board fence that kept curious wanderers out of the grounds, “here we are, Sky Squad—ready to begin to learn how a crate is started, what the design means, and why certain things have to be planned for—and then, what goes into construction and why, how she’s put together, and then, how to fly the finished crate.”

Sensing from his tone that he wanted them to concentrate, at least outwardly, on airplane construction and to let the other part of their activity be kept quiet, the three comrades agreed by assuming an interest that was by no means hard to pretend, when he took them into the offices, introduced them to some of the men working there, and explained that he was going to put them to work “to learn to build crates from the prop to the tail skid.” Barney, on the way, had learned their special interests. Therefore he put Bob into the engine assembling division where he could learn more about radial engines and the experiments being conducted with oil-burning types. Curt, who was methodical, cool and careful, was assigned to work, at least for awhile, in the wing assembling rooms. Al, being rather young for too much technical understanding, was assigned as helper to a “rigger,” who had been grumbling for some time at the laziness of his present assistant.

Everything was so new and so interesting that the trio forgot the seriousness with which Mr. Wright had assembled them that morning; but as they rode their bicycles toward home at lunch time, Bob imparted information that both startled them and turned their minds back to the serious business really underlying their work.

“I heard some talk, this morning,” Bob told his brother and Curt. “It’s serious, fellows! Missing parts aren’t half the puzzle—and tampering with airplanes isn’t all the rest.”

“They think, in the wing assembling room,” Curt put in, “that the airplane fell this morning because something went wrong with Mr. Tredway. The plant owner was delivering that craft himself. They all argue that he must have had a heart attack, or something of the sort, because the airplane was tested and gone over thoroughly. They say he must have been taken sick and lost control. Is that what you mean?”

“I heard some ‘mechs’ saying they think he deliberately made away with himself because of money trouble or something they don’t know about,” added Al. “Maybe trouble with his family, one says.”

“The talk in the engine plant was that some enemy deliberately tampered with that airplane because—because he knew the owner was to fly it.”

“That makes the puzzle about missing parts and the rest unimportant,” Curt commented, thoughtfully.

“Well,” corrected Curt, “not two separate puzzles—but a double puzzle, all the same.”

“It’s all one problem,” Bob explained to his younger brother. “But it has two sections. First—was the airplane tampered with as an act against the aircraft corporation or against Mr. Tredway in person?”

CHAPTER VI
SUSPICION AND SUSPENSE

Full of their horrifying suspicions, Curt and Bob rode on. Al turned off on a side street to deliver a parcel at the home of his new boss, “Sandy” Jim Bailey, the rigger. Al wanted to “make himself solid” with the sandy-haired man whom he already liked and whose grumbling was over now that he had, as he said, “a willin’ and brainy helper.”

Curt ate lunch with Bob. Both were disappointed when Bob’s mother told them that his father had been called out of town on his case, accepted earlier.

Riding back, to rejoin Al, who was waiting at the gate of the plant ground, Bob accosted his brother in some surprise.

“I had it,” Al told Bob and Curt. “I delivered that package for Mr. Bailey, and met his son, Jimmy-junior. He’s just about my age, and an awfully nice fellow. He invited me, so I stayed.” He dismounted and set his wheel inside the enclosure. “You ought to see the model airplanes he builds. They’re great!”

“Well, we can’t stop to talk about them now. Mr. Barney Horton left word with the gate-man we are to come into the administration offices to see him.” Bob led the way as he gave the information.

“Be careful, Al,” his brother warned him. “See that you don’t let anybody guess that you see any suspicious things. You show everything on your face, you know.”

Barney greeted them in his private office and introduced them to Mr. Tredway’s partner, Mr. Parsons, who was there.

If his manner was somewhat abrupt and his mind preoccupied, Bob made allowances for that. The man was overcome by the mishap and its sinister outcome.

His restless, seemingly uneasy, and almost furtive actions, however, were not so easy to account for. He seemed unable to meet the eyes of the comrades directly, and appeared to be nervous—even more than the circumstances justified, Bob thought.

Almost on top of the introductions he hurried out, “To get out there where the airplane cracked up and see what’s what!” he explained.

“He takes it mighty hard, he does,” Barney told the youths. “No wonder. He’s Mr. Tredway’s partner.”

“But there isn’t any real certainty that anything terrible happened to Mr. Tredway,” asserted Curt. “He might have jumped clear.”

“Yes, and maybe he was hurt, and managed to swim off to some part of the shore and wasn’t able to go any further. They haven’t searched every possible spot have they?” Al was hopeful.

“I’m afraid they have,” Barney replied. “Furthermore, there are so many soft, muddy sink-holes in Rocky Lake——”

“I don’t know, my lad. You see, it’s a good idea, having you here. When I’m around the people shut their mouths. But you hear things. What are they saying?”

“They think it’s something worse than missing parts and damage done to the ‘crates’,” Al answered and explained, calling on Curt and Bob for their versions of the talk.

“Hm-m-m. Well, Al, I think—if I were you—I wouldn’t listen to the talk around the plant too hard. Pick it up, of course, but don’t go making any theories of your own out of it.” Barney explained that people buzzed like a lot of flies every time anything happened, and that many of the less sensible ones, liking to be “in the limelight,” worked up almost idiotic theories. Usually, if they were accepted, they led to unjust suspicions, he argued.

“Those scatter-brains only want an audience to listen to them,” he declared. “I’d advise you to listen and let it go out the other ear. Otherwise you may get off onto the wrong notion. Better watch out for suspicious actions, and leave the theories to Mr. Wright.”

“Only temporary, I guess. Anyhow, you can tell me what you hear and see, and let it go at that. I’ll communicate with Mr. Wright, and if he thinks there is anything as bad as you say, I can tell you how to go on.”

The designer and the engineering staff were introduced and several hours were devoted to discussions between them, for the benefit of the trio, about airplane design and the things that had to be taken into consideration.

“If my young friends are going to learn airplane building,” Barney asserted, “it will be better if they know how important it is to figure stresses, safety margins, stability and so on, before ever a design gets on paper.”

“I thought all those things came out in the tests, after the airplanes are built,” Al contributed.

“Oh, no,” the designer said. “The tests show us how well we figured and how good the designs are that we created. But we work everything out up here before ever an engine part is cast, a fuselage built or a wing assembled.”

While they learned the many sections into which an airplane design is divided, and how carefully every curve, streamline, distribution of weight, lift of wing and drag of body must be calculated, Bob decided that no one in the office—at least no one with whom he came in contact—was acting in any suspicious manner.

Able to do nothing about the accident, the staff went on with its accustomed work, sadly, more seriously, to be sure, but steadily.

However, when Bob returned to his engine assembling work, he met a new character, and one of whom he at once formed an unsatisfactory opinion.

By association of ideas Griff Parsons fell under his suspicion because the youth, about eighteen or nineteen, was the son of the man Bob had seen in Barney’s office—Mr. Parsons. Griff, whose handclasp was flabby, whose eyes were even more shifty, whose manner was still more uneasy than his father’s had been, did not impress Bob favorably at all.

Assigned by the engine department foreman to help Griff fit piston rings onto the small pistons, to fit the piston assembly into the cylinders, before the final assembly was made, Bob learned much, and somewhat more about Griff than about the nice adjustments of machinery.

If he turned suddenly, Griff almost jumped, having hard work to control his muscles.

When he spoke of the morning’s accident, Griff, with a scowl, told him to “Keep your mind on what you’re doing! That other ain’t any of your business!”

Bob had hard work not to show his antagonism to the gruff, snappish young man; he was grateful when a summons took him out into the yard.

“I think it is a good idea to have you fellows treated as though all you are here for is to learn about airplanes,” Barney greeted him. “Your Cousin Langley is going to take up the sister ship to the cracked up Silver Flash, this afternoon, and I’m sending all three of you with him. It will give you a chance to understand what the designer told you about how carefully he had estimated the shape and weight of the new type longerons and how some mistake that he hasn’t been able to figure out yet makes the new crate tend to slip off sideways too easily. Langley will show you how he checks and reports, and then you will understand how every one of us works in harmony with every other one, to build our ships airworthy, safe and steady.”

When they joined Lang, who was busy checking his dashboard instruments as the engine warmed up on the line, Bob, Curt and Al did not hook safety belts on. They had every confidence in Lang’s ability to handle the ship, and they were more anxious to be near him so they could talk than to sit along the cabin sides unable to communicate their news to him over the roar of the engine.

As soon as Lang sent the powerful engine into speed, racing down the runway into the wind, lifting the elevators to catch the propeller blast and tip upward the nose, then flying level, just above the ground for those essential few seconds in which flying speed was regained before the climb, Al opened the conversation.

“Lang,” he cried, pitching his voice to offset the noise about them, “did you know what they are saying about the accident?”

“This seems to be a test flight,” he said. “But I’m really flying over to the airport, in the city suburbs—Barney wants you along to scatter and pick up talk there.”

“Barney thinks that mysterious crate we saw in the field might have something to do with it,” Lang responded to Curt’s question.

“He’s older, and better able to see things clearly,” Lang reminded him. “So we will climb pretty high, as if for test dives and slips, and skids, and barrel rolls—you’d better be sure to snap your safety belts—not right now, though. This crate slips pretty sharp. But——”

“In the first place, the airplane was carefully hidden. No one at the airport would know anything about it. In the second place, I can’t see how it could link in with the crash——”

“Unless its pilot was higher than Mr. Tredway, and flew over him and forced him down—” Al was excited at his deduction. He felt puffed up.

“By the way,” Bob broke in, “let’s talk about something else. If Barney sent you for information, that’s that. Never mind what we think. What I want to do is to get a line on that fellow named Griff—Griff Parsons.”

“Why?” Lang swung in his seat, catching the shift of the crate with almost automatic movements of stick and rudder bar. “What about him?”

“Yes,” Al broke in, “and what’s more, I suspect that ‘super.’ He looks like the sort who could do tricky things. Did you see his eyes?”

“He looks like the same type as his father—same shifty eyes, same restlessness—furtiveness!”

“Say! See here!” Lang became suddenly angry. “You let that young man alone and keep your unfair suspicions off him.”

“Is that so?” Al was angry, too, all at once. “Who are you to give us orders?”

“I’ll let you know who I am if you go on suspecting innocent people. What’s more, I’ll have Uncle Fred yank you out of there so quick——”

“What makes you so hot under the collar?” demanded Bob. “What is it to you if we suspect Griff? Is he an angel that we have to keep our minds off him?”

All of them were angry. Curt, not related to the others, felt that he ought to intervene between the quarreling cousins, but something in the unreasoning fury of Lang’s next words stopped him.

“See here!” Lang forgot he was piloting an airplane, and swung around on his seat, his face working. “If you keep on, if you bother Griff, or try to trail him, or anything—I’ll have Uncle Fred yank you out of there so quick——”

Forgotten, the airplane, with no guide, answered automatically to the thrust of Lang’s foot on the rudder bar as he whirled on his cousins. The shift of the rudder swung the nose, and Lang’s instinct made him operate it to make the ailerons bank the ship, but she had almost lost flying speed, the all important velocity which gives the wings lifting qualities.

Sickeningly the airplane tilted. Al, Bob and Curt, not strapped fast, tumbled sidewise, and the unstable craft tipped down.

Abruptly, realizing the slip and the danger, although they were quite high, Lang “kicked rudder” sharply.

To his dismay, there came a dull, snapping thump and one end of the rudder bar worked free.

And, with its unstrapped occupants in a huddle, on the side which was lowermost, the lower wingtip turned straight downward, the other pointed toward the sky, the windowed sides were in the position of floor and ceiling—and the airplane began to fall!

“Three thousand feet,” Lang’s eyes consulted the altimeter. “Three——”

CHAPTER VII
IN THE FALLING ’PLANE

In an emergency, thoughts leap through some minds quicker than lightning crosses the sky.

Bob’s mentality was of that type. Whether his mind worked through what is called instinct, or whether he put together many things he had learned about airplanes, or whether he worked through a chain of reasoning from beginning to end in a fraction of a second does not matter.

In an airplane which is falling with wingtips toward sky and earth, the ailerons which usually tilt it are practically useless, because it has no forward movement sufficient to bring the air against the leading edges of the wings for lift, or to press against the ailerons to cause them to function properly.

Furthermore, when the ship is falling “on its side” the elevators which in level flight serve to lift or to drop the nose, are no longer elevators; they, because of the position of the ship, are really the rudders, while the rudder, because it is then parallel to the ground, assumes the position and functions of the elevators.

But Bob knew, in a flash, from the action of the ship, from the free movement of the rudder bar, that the rudder cable had come loose or had snapped.

Bob knew, furthermore, that unless he could drop the nose, “give her the gun,” and thus—by partly diving instead of falling sideways, and by partly using the propeller pull—could regain flying speed, Lang could not get the craft under control and save them from a crash.

It must be done before they came too close to earth to make the maneuvers, necessary to a safe landing, possible.

Even as he called to Lang, “Give her the gun!” his hand smashed through the thin side of the cabin wall, down where it came together with the sturdy, but light plates of the flooring.

Because the airplane fell on its side, the side he smashed was under him, the flooring was at his side, acting as the sidewall.

He knew that if the lower of rudder cables in the ship’s present position was broken he could get it there; if the upper one was severed its end would have dropped down, perhaps caught on a longeron or on a longitudinal fuselage brace; he might be able to catch hold of it.

It took but a second to thrust his hand through the cabin wall, to grip the edge of a floor plate, to rip it from its temporary fastenings which were not completed until the tests made it sure that no further adjustments under the flooring would be necessary.

Braced so that his body would not crash down through a window, he looked, and grappled for the cable end. His fingers touched cable!

For all the exigency of their desperate situation he tugged very gently and was glad. That cable was fast! It might lead to the elevators, the ailerons. Anyway it was not the right strand.

Again he felt under the edge of what was in the ship’s position, the plate above the one ripped away. His fingers touched a loose strand.

“We’re all right!” he panted, grasping the plate and tugging it partly free so that his arm could go further in and secure in his gripping fingers the loose cable end.

In the brief time that this had taken, Lang had obeyed the call for gas to be fed to the engine. Idling, it roared into its power pulsations.

If the cable he held were pulled and it depressed the rudder, which would act in their position as an elevator or “flipper” acts, all would be well. In that case, the propeller blast striking the rudder airfoil would push the nose downward, and the ship would begin to dive; then the air, rushing against the leading edge of the wings, would cause them to be operative, even in their sidewise position, and with the dive and the engine pull giving flying speed, they could then maneuver.

But if the rudder went upward, it would lift the nose. Already deprived of all but the little speed the engine had picked up, the blast on the rudder, lifting the nose, would cause another stall, and they would perhaps fall too far to get the other side of the rudder cable before he could help it.

Lang, with a swift glance toward the windows, which faced the earth, saw the ground seeming to leap upward toward them. Above was the silent sky. There was a little margin of time—if——

“Can you pull the rudder further?” The message came swiftly from Lang, through Curt and Al, to Bob, almost out of one mouth before the other said it, so quick was the response.

Slowly the ship swung onto a more level keel, and while Bob clung with fingers that were growing numb from his excitement, the ship got flying speed, in a sort of descending spiral, the elevators could again be made to lift the nose as flying speed was attained, and the ship was in control.

The signal to ease off did not come at once. Lang preferred to hold his present bank and circle, while he looked over through the lower cabin windows to sight their position.

In that brief time Curt, also keyed up, had located the loose end of the cable that led from the rudder bar; with a piece of strong twine he made a splice, securely reaved onto the loose end, led it to the free end in Bob’s fingers, and, since the rudder was hard down and could be held there by grasping further along the cable, Bob shifted his grip until Curt was able to get his twine, doubled, fast on that part of the cable also. Then, while Lang held his rudder bar steady, Curt tightened gently until the ends of the severed strand were almost touching, made several knots that could not slip—and the entire control of the ship was in Lang’s hands again!

They did not feel like going on to the airport, but Curt, always cool, generally far-seeing, urged that they do so.

“If we go back, we’ll have to tell about this, and create new excitement and talk,” he counseled, and Lang saw the good sense of the idea.

“We’ll go on, and land at the airport,” he agreed, above the sound of his motor. “After we get over our excitement we can think better.”

When they got there, and Lang telephoned the aircraft plant, the trio, outside the booth, heard him ask for Griff.

One and all they linked Griff’s uneasiness and Lang’s curious anger and immediate call to the one he called “a very good friend.”

CHAPTER VIII
WATCHFUL WAITING

Moodily walking back toward their airplane, around which a group of handlers and mechanics watched one assigned to make sure the cable splice was entirely safe, Curt spoke quietly.

“I hate to suspect your cousin of anything wrong,” Curt assured the brothers earnestly.

“Not any more than I hate it,” Al retorted. “But you’ve got to look at what you see and hear what comes to your ears.”

“All the same,” counseled Curt, hoping to lighten the burden of unhappiness for his chums, “I’d go slow. You know—they may be just friends, close ones. There may not be anything wrong about Griff. We are likely to be suspicious, because that’s what we are there for.”

“But look!” objected Al. “The cable snaps. Now that’s almost a spick-span new crate. That cable ought not to fray apart—it could never wear so soon. It was—filed or scraped.”

“But that doesn’t involve Griff,” urged Curt, hoping, if he lightened their suspicion of Griff the cousin who was his friend would be less suspected. “He works in the engine department. Anyhow, he knew his friend, your cousin, would fly the ’plane. He’d never——”

“I talked to Griff,” he said. “Told him what had happened. He was flabbergasted.”

“Why did Griff have to know anyhow?” Al was impulsive and did not care if he started a fresh quarrel or not. The conclusion he jumped to was that an angry Langley would disclose “secrets.”

Langley walked away. But they did not let him get far ahead of them as they approached the airplane.

“Funny about that cable,” he stated. “How did it ever get so much use that it wore through? You must kick rudder every two seconds.”

“Was it worn through—or—” Al began. Curt prodded his ribs very sharply. As Al became quiet Curt asked a louder question to distract the man from pursuing that “or—” and learning their fears.

“It chafed against the transverse brace it ran under,” the mechanic responded. “They ought to have an eyelet or something for a guide—a small pulley would be best, with an eyelet to keep the cable from slipping out of the groove and chafing on the solid part of the pulley.”

The plates had been fastened back into their light frame, being of sturdy construction and not permanently attached, they had come away clean and were put back easily. Only the cracked hole in the panels gave outward evidence of the recent near catastrophe.

“Suppose we let on that was an accident, that I put my foot through the panel,” suggested Curt. “Repairing it only means putting in a new section there—it ought not to cost much and I have some money in my savings account to pay for it.”

The best way to do that, argued Curt, was by watchful waiting, not by putting the possible malefactor on his guard. “They could,” Al declared, “see who makes the repair, and I can watch, being out near the ’planes, and see if anybody takes a special interest in the floor and the cables.”

Langley agreed rather bruskly and went off to take up his inquiries about the brown airplane they had seen in the field.

“Watchful waiting!” repeated Bob, thoughtfully. “That’s a good slogan. Let’s ‘watchful wait’ to see what Griff does—and how Lang acts—and if either of them acts queerly when they are with Griff’s father.”

“Just what makes you suspicious of him—the father?” Curt asked, more to check up his own theories than for information. “He’s Mr. Tredway’s partner, you know.”

“I suspect him,” Al declared, “because he’s the kind that looks suspicious, with his quick action and his sharp talk and his shifty eyes.”

“All right—we won’t watch him. But it’s bad, because we can’t talk over plans and tell him everything. There will be—a—a——”

“Well, pretend to be the same as ever, but keep your ideas to yourself,” Curt begged. “And—we’ll be watchful waiters.”

During the next week that was the only policy they would have been able to adopt. Nothing happened at all.

Al still carried parcels, on occasion, for rigger Sandy Jim Bailey, and improved his acquaintance with Jimmy-junior.

Mr. Wright’s absence from town during the entire week prevented them from consulting that detective. The comrades were thrown on their own resources.

“I don’t see that watchful waiting has gotten us very far,” commented Al as they rode home for lunch, Curt with the brothers, at noon on Saturday. The day’s work was over.

“We know a little more than we did,” Curt reminded him. “I’ve had talks with some of the boys I know, and I’ve found out that the ones Griff associates with aren’t thought well of. And Bob has trailed him, several evenings, in spite of Lang’s warning to Griff, and Bob has told you that Griff always gets away on his motorcycle and goes somewhere that we can’t locate yet. But we know his character isn’t very high class, and his father still acts uneasy and preoccupied. So we have gained that much.”

“What good is it?” Al was unconvinced. “It doesn’t say what happened to Mr. Tredway. It hasn’t told us who is taking airplane parts. It doesn’t explain who tampered with the rudder cable in the Golden Dart—or why.”

“No,” Bob admitted. “That’s true, it doesn’t. But it’s the best we can do, for the present. And we never know when something may ‘break.’”

“Let’s keep on learning airplane technique,” suggested Curt. “We know we’ve gained there, anyhow.”

“Yes,” Al nodded. “I can name the different parts of a biplane without stumbling over any of them.” He did, “—fuselage; engine; propeller; upper and lower wing; cockpit and its cowling; struts and landing and flying wires; stabilizer, fin, elevator, rudder; ailerons; tail skid; and landing gear that Sandy calls the ‘trucks.’”

“Correct,” agreed Curt. “And they comprise five groupings, each one having a special purpose—the fuselage, the supporting structure for everything else. Everything is attached to that. Then——”

“The second group,” Bob cut in, “is the supporting surfaces, the wings. They sustain the whole weight in the air, and the flying wires take the lift of the wings as the air sustains them, and communicates it, with the struts helping, to the body.

“Well, in a way,” Bob changed the statement slightly. “The flying wires are to take the stress, and if it wasn’t for them the wings would tilt up at the ends or tips, like a ‘V.’ The flying wires take the stress in flying the same as the landing wires take the weight of the wings in landing; without the landing wires, when the ship came down the wings would crumple down over the crate like the two slanting sides of a tent or like the ‘V’ upside down.”

“Yes,” Al showed his knowledge, “and then there is the control group, the ailerons at the backs or trailing edges of the wings, to be moved upward or downward, to tilt the ship; and the rudder, to turn it sideways—and if it’s flying on its side the rudder is performing the office of the elevators and they of the rudder, because when it’s flying level the elevators are to tip its nose up for a climb or down for a glide; then there’s the fin and the stabilizers that give it balance and help to hold the whole ship in whatever position it is placed by the movable controls I just mentioned.”

“And with all those you have a glider,” agreed Bob. “The engine, and its ‘prop’ are for motive power, and the landing group, either wheels for the earth, or pontoons for the water, or both, combined, in an amphibian, for land-and-water use——”

“We know some things,” agreed Curt. “But we don’t know where Mr. Tredway’s body went—or——”

“What Griff is going to do with his Saturday afternoon,” commented Bob. “I’m going back to the plant, and pretend to finish up work, and see what happens there while it’s supposed to be closed down.”

CHAPTER IX
STRANGE ACTIONS

Although the aircraft manufacturing plant observed a forty-four hour week, closing down on Saturday afternoons, when the three members of the Sky Squad returned, about two o’clock, they were somewhat startled to discover that their “suspects” were there.

The youth was surprised, “caught in the act!” mused Bob as he saw the youth, with furtive, hasty actions, completing the wrappings of a smallish package which he hurriedly slipped into his coat as he turned aside, trying to conceal his action from Bob and then, noting that he was caught, trying to pass it off as an ordinary action.

“So that’s where some of the smaller parts are going,” Bob concluded, pretending not to be aware that anything was wrong.

“Hello,” he greeted. “I thought I’d come back and take that model engine apart, while no one was here to bother me, so I can get it straight in my head just how the valves operate.”

“Yeah?” Griff was inclined to be gruff, and as he tinkered around trying to pretend to be busy, but, to Bob’s notion, watching the member of the Sky Squad, the latter gave every impression he could of ignorance that he was being supervised, studied, observed.

Had Griff been intruded upon before he finished what he had been doing? Bob wondered as he took off the cylinder head of a small, roughly assembled model of a new design for a Vee-type motor they were working on. It appeared that Mr. Tredway had been “all for” the newer radial engines, while Mr. Parsons exerted all his influence to introduce the model in which the cylinders, in line, came together in a slanting fashion, like a “V” at the crankcase jointure.

“Hello, Griff.” He nodded, paid little attention to Griff and went over to Bob.

“I see.” Curt, bent close, whispered his next words. “Lang is out in the yard, working on the Golden Dart. He has the plates out and he is——”

“Say, Curt,” he called, “run up to the offices, and if Mr. Parsons or Barney is around, get me a new—er—length of cable, will you?”

“Go to the supply room, on the ground floor. The watchman will let you get what you want. All you have to do is to write out a requisition form and put it on the spindle on the desk. You’ll see it.”

In the offices, as he neared the open door of the bookkeeper’s little cubby of a room, Curt heard two low voices. He hesitated. He was close enough to be able to recognize in the bent figure leaning over the other, with his back turned, the peculiarly checked brown suit which identified Mr. Parsons.

Evidently neither the partner nor his companion heard Curt, so absorbed were they in some discussion or comparison of figures.

Curt, wondering why they were so engrossed in that work when the office was closed, and so absorbed that they had not heard him—he had not tried to snoop or to creep along the hall!—decided that it must be legitimate business, and that he would not disturb them.

“It’s an earth inductor compass,” Al explained. “You heard Sandy hail me as we came in.” Curt nodded. “He stayed on to check up my work,” Al informed him. “I’m pretty raw, you know, and Sandy is so good-natured that he didn’t want to see me get into any trouble. I was helping one of the mechs this morning”—he had already picked up some of the slang, shortening “mechanic” as did those in the plant—“and Sandy was going over the instruments I had installed. That Golden Dart is going to be used for an overseas hop, he says—and—” he went close to Curt, “Curt, I think Sandy has helped us to get a line on somebody else to suspect—about the stolen parts, anyhow.”

“He called me over and told me, in a joking way, I had a lot to learn. And then he asked me if I knew anything about how this new type compass operated. I knew a little, but not much, and he showed me how little I knew. Curt—” he was very serious—“this is an old, broken thing. Look!”

“If we’d let that get to the checker, Monday, I’d have been suspected of getting away with the regular, real one. This must have been substituted by the mechanic who was on that job—the one I helped. Or else it was given out by the clerk who has charge of this room. Anyhow, Sandy says I ought to put in a requisition for another one, and then he is going to help me keep an eye out to see what happens on Monday. He wants to help us. I saw he was so afraid I’d get the blame, and he’s so mad about the way things are being taken that I let him in on our secret——”

“Well, only as far as saying we were crazy about aviation and had formed a sort of order we call the Sky Squad, and naturally, being honest, we saw how things were going here and wanted to do what we could to discover who is taking parts.”

“He said not to be too hasty to jump to conclusions. He told me that this substituting of the old inductor compass looked like the work of the mech, but it could be the supply clerk, or, maybe, somebody outside the plant entirely who had sent it in, boxed, in a new consignment. He said the safest way would be to put in a new requisition, then we’d see who acted guilty when it was discovered. If the supply clerk is guilty he would never mention it for fear of being caught. If the mech is the culprit, the clerk will raise a howl about the exchange. If they are both innocent, you’ll hear from both of them, and we can trace it to somebody who sent the consignment.”

“Good stuff!” agreed Curt. “But didn’t the mechanic notice it was a broken model of the compass?”

“He gave me the instructions how to assemble it and told me to be careful, and then went over to work on that small speed craft that Griff is testing out. Griff called him, so it looks all right. If the mech noticed this old compass, before he went home, he’ll tell me, first thing Monday. If he knew about it and had taken the other, the good one——”

The watchman, making his rounds, observed the pair. Readily enough he admitted them to the supply department. Either he was of too unsuspicious a nature, being rather dull, to wonder or question; or he had been told by Barney that the youths were especially privileged. In either case he made no comment as they found the cable Curt wanted for Lang and the several extra inductor compasses, neatly boxed, among the stacked instruments in the shelves.

Making out two of the slips he saw in a pad, and fixing them on the upstanding spike of a file, Curt handed Al his box and with the cable went to find Lang.

Handing the strand to his chum’s cousin, Curt decided to return to the office building to see what he might see. The excuse that he was studying the blue prints of an airplane would furnish reason for his presence in the office if Mr. Parsons was still there and asked.

“Sure is,” admitted Bob, watchful, quiet, but willing to follow Griff’s unexpected lead.

“Lang says you had your suspicions of me,” Griff grinned, quite pleasantly. Had he, Bob wondered, been “tipped” by Lang to cultivate friendship? Was there something really underneath the friendship of the partner’s son and Bob’s pilot cousin? Was there something else?

“Why, I suppose when we got excited about that broken rudder pull, we thought of anything and everything,” Bob grinned also.

“Well, you thought wrong, friend. Would you try to do any harm to your buddy, Curtis, if you knew he was to fly a certain crate?”

Bob had not in any way considered that possible solution. There was another test pilot, not as popular as his cousin. He gave the most serious attention, but Griff evidently felt that he had said enough, adding only: “But I don’t mean to accuse anybody. Let’s forget it. Come on, let’s forget motors and go up and have a look at them little fleecy clouds.” He caught Bob’s arm, after slipping the cylinder head over the pistons of the model with Bob’s help.

“Not solo!” Bob admitted, “but Lang has let me take the controls six or seven times when he used to take us up, before we came here to——”

“To learn all there is about building airplanes,” Bob continued without the flicker of an eyelash.

“Hm-m-m! Well, come on, kidlets! I’ll take you up in the prettiest little crate you ever sat in—what’s more, I’ll give you some experience so you can fly them crates after you get wise to how they’re assembled.”

It was evidently a genuinely friendly offer. If it had any hidden motives, Bob, on that sunny Saturday, with a gentle, warm vacation wind blowing, with bonny clouds drifting slowly, gave up watching and went in for air experience.

Al, finally deserted by Sandy, who had errands down town, saw Bob and Griff warm up the little speed sportster he had been rigging. A little envious he watched the check-up, the trial spurts of the fast little engine, the take-off and the soaring of the handsomely designed craft. Then he went on to visit Jimmy-junior, whose father, Sandy, had given him a special invitation to spend the afternoon and to stay to dinner with Jimmy-junior.

Lang, taking the cabin monoplane for a test of his rudder performance, called Curt to go along; so the trio lost interest in detective work and concentrated on enjoyment——

CHAPTER X
A SUMMONS

While Griff, who handled an airplane expertly, was executing dives and slips, barrel rolls and figure eights, and a loop or so to demonstrate his skill, Bob, in the rear cockpit seat, wondered whether Griff was trying to frighten him.

That was not his purpose, Bob decided, and he was more convinced when Griff, with a grin, turned, after waggling the stick and holding both hands up beside his head—the signal to “take control.”

Under Lang’s tuition, in several airplanes, during tests, Bob had been permitted to handle the stick, rudder and throttle. He knew the elementary movements of straight flying and had some of “the feel of the air” which comes to any person who has the flying sense: that “feel of the air” is akin to knowing what the ship is going to do and, of course, sensing how to meet its various tendencies. When, during a climb, with too steep an angle, the controls begin to get “loggy” for an example, the born pilot, or the trained fellow with his air-sense developed, knows instinctively that the ship is about to stall, and automatically drops the nose and picks up flying speed.

For awhile Bob, flying straight, or banking and turning, remained near the small flying field of the plant. He knew the signals with which a flying instructor guides his pupil, and, handling the dual control section in his own hands, and with his feet, he made simple maneuvers under Griff’s direction, and seemed to please Griff by the quickness with which he caught the corrections signaled to him when he over-banked, or let the ship skid too long without catching the skid.

The trial was over all too soon, and as Griff took over to shoot the field and set down, the most ticklish part of flying tactics, Bob felt a trifle sheepish for having suspected him.

However, Bob began to think. This sudden affable manner must have some reason behind it. Furthermore, he decided, Griff might be trying to win his confidence through the hidden flattery of telling Bob what a “corking” pilot he would make with a little more training. Bob knew that flying is taught carefully by any self-respecting school, that a thorough ground-school training and many hours of instructed flight will be followed by many solo flights, with intermittent check flights under the instructor’s eyes, before a pilot is considered more than a student. Griff over-flattered.

Bob, as he went home, where Al and Lang had preceded him, his cousin having stopped in for dinner, decided that he would accept Griff’s offered friendship with a grain of salt.

Al had already eaten his dinner, with Jimmy-junior, after a fun-filled afternoon during which Jimmy had displayed his airplane models, had supervised many trials while he let his guest wind the sturdy rubber band motors and set the tiny, practicable controls of the toys. Furthermore, he had talked about the Sky Squad idea and had begged to be permitted to join, being air-crazy, as he put it. Al, promising to take the matter up with his brother and with Curt, had said he would do all he could to induce them to agree. He could not broach the matter, however, as Curt, Bob and Lang ate, because Lang was full of the excitement of receiving a telegram from Bob’s and Al’s father, the detective, from a city about fifty miles away, asking Lang to come to the city for a report and a conference.

Glancing at Bob, both Curt and Al saw that the older member of the secret membership was disturbed in his mind. Lang would not tell about Griff, as he visited his uncle over Sunday. That was what Bob was thinking, as Al and Curt saw. But Curt, looking at his watch, reminded Lang that he must stop stuffing down the filet of sole, a form of fish steaks of which he was extremely fond, if he expected to “make” the ’bus that would pass the house on the way to the city, and the railway station.

“No. I’m going to borrow Griff’s sport model. More speedy and I want to check before it is turned over to him finally.”

Bob pushed back his chair as Al and Curt sprang up. Lang, rising with his superior, amused grin at their anxiety, waved them back and kissing his aunt and thanking her for the fish he loved, he departed.

“I’m going!” said Bob, and explained excitedly to his mother that he had information of importance.

They could not explain to their mother that they suspected Lang, at the very least, of protecting Griff, a friend but not a desirable one. Whatever their own ideas they were none of them blabbers.

Bob ran out on the porch, leaped down the steps, hopped on his bicycle and pedaled down the first side street. He was not entirely sure of his plans, perhaps he half intended to secrete himself in the fuselage of the ’plane, to go on as an unsuspected passenger; possibly he hoped to induce Lang to take him by getting there first.

Griff, at the gate, was in close communication with a mysteriously furtive stranger!

CHAPTER XI
A TRAIL AND A FLIGHT

Twisting his handlebars sharply, Bob sent his bicycle into brush at the end of the aircraft plant grounds where the fence turned; he wanted to get out of sight.

The pair at the gate were having some sort of argument and probably had been too excited and absorbed to notice him, Bob decided.

He dropped his wheel and crept back to the corner of the fenced enclosure to watch.

From that position he could see the man, but only part of Griff’s coat and an arm. The man, as he saw, was vigorously arguing. Griff must have been either pleading or arguing, Bob guessed, from the man’s violent gestures and appearance of “laying down the law.”

Bob recalled that he had seen Griff wrapping exactly that sort of parcel earlier.

The man took it, put it rapidly into his coat pocket, inside. With a quick look up and down the deserted highway he swung and crossed to a car parked on the opposite side of the road. Climbing in he speeded up his engine and drove away at constantly increasing speed.

“So they are dividing the ‘spoils’—or Griff was giving him money.” Bob, unable to see Griff, not daring to emerge from his concealment, made the deduction under his breath. “Well, now shall I follow that man? No, because his car is too fast. I can’t catch him on my wheel.”

He decided to wait where he was, to see what would happen. To go in at once might alarm Griff. He might realize that Bob had been near enough to see what had occurred; he might suspect. Bob wanted to keep his presence unknown; Griff had already been warned by Lang; he would jump to the conclusion that Bob was watching.

Griff, as he watched, ran wildly out into the road and began to wave and shout after the receding car.

Griff, while Bob stared, dashed back into the gateway. For a moment Bob wondered where the watchman was, then he saw the man, in a small ice-cream and soda water shack, a little distance down the road opposite the fenced property. Griff, Bob guessed, had offered to watch the gate while the man refreshed himself.

The last question was answered by the pop-pop of a motor. Bob knew that Griff rode a motorcycle. He was getting it started. He meant to pursue that car for some reason. Something had caused him to want to talk again with the car driver, Bob mused.

While he watched, keeping all but his head concealed, the motorcycle, with Griff mounted on it, came sputtering into view.

Never glancing around, opening his throttle, he pelted down the road after the car.

Bob, without hesitation, rushed his bicycle into the highway and pedaled after the motorcycle for all he was worth. Griff was too intent on his purpose to notice, he felt sure.

It would be a losing race, Bob feared, unless Griff overtook that rapidly receding car very soon. Muscles could not endure against a machine! Nevertheless Bob rode as fast as his pedals would turn.

As he sent the wheels spinning along it crossed his mind that Lang would be arriving at the plant almost any moment but he kept on all the same.

“It will take Lang awhile to warm up the engine, and, anyway, if I don’t go with him I know another way to communicate with father,” he decided.

The car was almost out of Bob’s sight, the motorcycle was rapidly overtaking it.

Far ahead, on a cross road, he saw a huge truck come into view. It was not only between the car and its pursuer; it was also well onto the road and almost directly in front of the motorcycle.

“Griff!” Bob shouted, without thinking that his voice would never be heard. He instinctively cried a warning. If the rider had his head low over his handlebars!——

His coaster brake jammed on, Bob slowed, alighted, his muscles refusing to function for the instant.

But during that instant Griff evidently saw the huge obstacle and swerved. In making the wild curve to go around the rear of the truck Bob saw the youth and cycle go off the road into the ditch.

Evidently unaware that anything had happened the truck driver kept on down the cross road. Bob, remounting, pedaled for all he was worth toward the scene of the accident. As he rode swiftly he saw other figures approaching.

At the point where the motorcycle lay on its side, he was met by Al and Curt, who had been approaching from the opposite way, up the side road. “We decided to come and see Lang hop off,” Al explained as the trio ran toward Griff.

He was sitting up, a little shaken, a little dazed, when they approached. Bob, seeing that he did not appear to be seriously hurt, caught Curt’s arm. “Look here,” he said quickly, “I want to go with Lang. Don’t say I was following—you know—keep it quiet. I must get to see father and tell him——”

Bob hurried off, as though he was in search of aid, and he felt, as he pedaled back toward the field, that Griff probably had been too much shaken to notice that Bob had come from the direction he had been riding, or deduce that Bob had followed him.

The watchman, and several others from the soda stand came running down the road. They called out as he approached and with a brief explanation that there had been a “spill” but that he thought it was not serious, Bob rode on.

He found Lang riding toward the plant, and swung his bicycle in at the gate and set it against the fence.

“Griff took a spill going around the back of a truck that came out of the side road. I think he’s all right.” Bob called out his answer to Lang’s shouted inquiry and saw his cousin ride on to investigate.

Bob, with some idea in his mind that he might crawl into the fuselage of the small speed ’plane, and, thus stowed away, be carried to the city from which his father had telegraphed, changed his mind. The close, smothery fuselage, subjected to the most violent rolling and heaving of the airplane’s progress, would probably make him ill. He preferred to stay outside, to see what happened, and to compel Langley to take him as a passenger.

Watching from the gateway he saw that Griff had been lifted to his feet and had apparently found himself only rather badly shaken. This was Bob’s decision because he saw a passing car driver help the shaken youth into his car, tumble the motorcycle out of the grass and turn it over to the plant watchman to be trundled back, and drive off to take Griff home, it seemed.

“Contact!” he cried, leaping aside to avoid the flailing, knife-like edges of the blades. The engine caught on the touch of spark to compressed gas mixture.

While Langley opened the throttle and warmed up his engine, Bob unconcernedly began to clamber into the after cockpit seat.

“Listen, Lang,” Bob leaned close to Lang’s ear to carry his message above the noise of the radial engine, “which suits you best? To have me with you, to tell dad what I know before your face—or to have me telegraph him while you’re on your way, and let you explain to him what I have to tell?”

“Oh—all right!” he grunted and “gave her the gun” in somewhat vicious spurts.

Bob, fitting on the “crash helmet” kept in the ’plane by Griff for him that afternoon, and the leather jacket and gloves, smiled.

He was progressing as a Master Sleuth, doing his share creditably for the Sky Squad.

As soon as the engine was sufficiently warm and methodical Lang had checked all his instrument readings, the trim little ship taxied down the smooth field to head into the wind which Bob saw, from the “windsock” blowing out from its mast on the office building, was from the south, a nice, light, Summer evening breeze.

The watchman, coming in, put aside the slightly damaged motorcycle and strolled across to the hangars, into one of which he stepped to throw a switch, lighting the flood light by which they could see to take off. He did not question Lang’s right to use the craft because Lang must have gotten its ignition key from Griff, its owner.

As they took the runway, and increased speed to the throaty roar of the engine, Bob felt that sense of the ship getting “light” which indicates to the pilot that she is ready to take the air. He saw the elevators tip, glancing around swiftly to check the safety of the way ahead, and then saw the lighted earth dropping, contracting into a spot of vivid light against a field otherwise dark; then the watchman shut out the floods to avoid confusing them in the air, and the ship climbed into dark night.

They had climbed several thousand feet and were headed into the north, so that Lang could “pick up” the lights of the airway along which his night flying would be easiest, when Bob saw him double unexpectedly.

For an instant the craft’s nose went almost straight down and Bob was glad he had strapped himself in; then Lang evidently caught control, and the stick, thrust forward as he doubled, with some unexpected convulsion or “stitch,” was pulled back and brought the ship out of the dive gradually.

“What happened?” Bob screamed above the engine noise, the song of wind through wires caused by their dive.

“Cramp!” called Lang, cutting the gun as he held a glide for a moment, turning a white face toward Bob. “Listen. Bob—oh!——”

He bent again. “The fish—too much fish—” Bob guessed, and had he known that Lang’s delay in reaching the field had been due to further refreshments, he would have said, “Fish—and ice-cream!”

At least that was a far more reassuring thought than Bob’s first idea, that some one had tampered with some control of this craft.

Suddenly, as he saw his companion in the forward seat double, Bob felt the stick waggle against his leg.

In an interval between his spasms of violent pain, Lang held up his two hands alongside his helmet.

“All right!” he called, and, with a steady hand, he clutched the stick of the controls in his cockpit, set his feet against the rudder bars, and eased his throttle open to regain speed.

He was not in the least nervous or flurried. He pitied Lang’s cramped stomach and evident suffering, but did not permit it to influence his steady nerve. He had been given enough lessons to know how to hold the craft in level flight. While night flying was not as safe and easy as daytime work, he knew that if he followed the ribbon of lighted highway that ran toward the beacons of the nearest airway, he could always “set down” on the asphalt, if worst came to worst, and if he did smash the trucks, the landing gear, he did not think he would do any more serious damage.

“Had I better set down?” he shouted, gliding for speed as he cut out the engine roar. Lang shook his head and gestured forward. Evidently he was not afraid of any immediate physical collapse and preferred to go on flying to see if he would recover. Bob held on.

He picked up the beacon and, watching Lang’s gestures, swung in a long, banked curve, to head across the wind down the unconfined airway, whose second beacon he could see, far away.

By habit looking around to be sure no other ship was close as he turned, Bob, startled, saw the flying lights of another craft pursuing.

It must be pursuit! It came from the direction they had come. It turned as they turned, only in a more sharpened bank, so as to cut off part of the distance, it seemed to Bob, to close the gap between them.

But as Bob opened the throttle to regain flying speed without having to dip down too low, there came from the other ship a red flare.

Lang considered. As he hesitated Bob guessed his thoughts. Some one from the small field, some member of the plant staff, probably Mr. Parsons, finding the ’plane belonging to Griff gone, and hearing from the watchman who had taken it, had taken off in the cabin monoplane to stop what he probably considered a prank of Lang and Bob—some night-flying lark.

They could outfly that cabin ship in the speedy, easily maneuvered sport craft—or, they could, with Lang at the controls. But Lang was badly upset in his stomach. What would he decide? Bob mechanically looked around for the best spot to set down.

Bob opened the throttle joyously. Here was adventure, pursuit, thrill enough to suit anyone!

CHAPTER XII
THE CHASE

The speed craft he and Lang occupied had much the best of it on a straight flight, but, against that, he had to set his inexpert handling. The smaller craft could out-climb, out-maneuver the cabin ship but he had no experience in stunting, especially dangerous at night.

To try to make a landing, Lang evidently concluded, was not wise. He felt that he could take over the controls before that need arose, Bob guessed.

If the cabin ship had the disadvantage of being slower, she had gained an offsetting advantage before they saw her. She was much higher in the air than their craft; she could dive, if her pilot chose, and thus close the distance between them—maybe come down “on their tail,” or ride them to earth, if her pilot proved to be determined to force them to land.

Accordingly Bob opened the throttle wider, and slightly elevated the nose to climb.

Instantly Bob manipulated ailerons and rudder correctly and felt the wind on the cheek toward the lower side of their bank, telling him they were slipping.

Then, applying rudder and other controls to check the slip, dropping the nose again to pick up flying speed quickly, he saw why the maneuver had been executed. The cabin airplane had begun to dive down from above them. Lang, having seen it, anticipated. He had not wanted to wrest away control—too dangerous. He had risked the signal, and Bob had executed his order accurately.

He was glad, all the same, when Lang shook the stick, tapped on his own helmet to sign that he wanted the controls.

Bob relinquished them thankfully enough. At night, in strange surroundings, in an airplane he had only handled a little, he was not foolish enough to wish to risk neck and limb—far less Lang’s than his own!—by trying to outfly a pilot who evidently meant to be vicious, to resort to war tactics if they did not obey his signals.

Lang, somewhat recovered, took over and Bob, delighted, watched his expert manipulation of the splendid little ship. She answered his every command. He barrel-rolled out of the way of any immediate danger, thus leaving the cabin craft well to one side. He started up a loop after a swift dive, but at its top he executed half of a barrel-roll, and since the top of the loop had the nose in the direction opposite their course, the half-roll put the craft on its level, upright course, but going directly away from the former one.

The cabin ship could not be stunted that way, or else its pilot against his will was compelled to recognize superior tactics.

At any rate, as Lang swung around in a wide circle, slowly climbing at the same time, the other craft seemed to be heading uncertainly back.

It came around, however, as soon as Langley straightened out on the former course along the airway; but they rapidly outflew it and when they landed at an airport in the distant city suburbs, the cabin ship was nowhere in sight.

It was nearly eleven o’clock at night when Bob and Langley were ushered up the hotel elevator and along a corridor and into Mr. Wright’s rooms.

The detective, who had been apprised, long distance, by his wife, that his nephew was flying to keep the appointment, was waiting.

Hardly had his surprise at Bob’s presence been expressed and a late supper for the air-hungered pair been ordered than another visitor was announced.

“Why didn’t you leave word that you were coming here?” he said, rather sharply. “We could all have come together.”

“So I was. The watchman said you hopped but he didn’t say where to. I was coming over to confer with Mr. Wright, but I thought Lang and you, Bob, were joy-riding. So I signaled you to land and when you didn’t I decided to scare you into setting down—but it failed.”

“I ought to know better than to think I could outfly Lang,” he said. “Well—if you’ve come with information, it’s all right. We can have a conference, all together.”

They did so, over the dinner. Lang listened to Bob’s recital of the latest developments about Griff, with growing anger, until he saw Barney’s face.

“Good boy, Bob,” commented Barney. “I’ve sort of had a notion in my head for some time about——”

“Yes. I’ve thought he was the one who’s crossed the wires on us and short-circuited the whole plant. So he divided with somebody, did he? Well—he must have gotten it from somebody higher. Have you thought about?——”

CHAPTER XIII
THE DETECTIVE’S THEORY

More startling than Bob’s fresh information was the revelation given by Barney, the information which had brought him, flying, to consult the detective he had engaged to solve the puzzling case.

Barney, because it was so late, gave only a hint; but what he said caused a great deal of sleeplessness on Bob’s part, at least.

“We got the wrecked airplane up,” Barney told them all, that night. “I’ve had it hauled in and dismantled.”

When, during their Sunday morning conference, he amplified his statements, the mystery deepened.

Dismantled, thoroughly examined, by Barney, in person—he did not trust any subordinate in so important a matter—the airplane revealed nothing wrong, either with its engine, with its wings, or with its controls!

“But it fell,” commented the detective. “What, do you imagine, caused the crash?”

“I give it up.” Barney was unable to make a theory. “I hired you to do the doping out of that! I give you the facts. You do the rest.”

“Bob,” his father turned to the youth, “have you jotted down all the suspicious things you mentioned, as I asked you to do?”

After consulting it and comparing it with a sheet on which he had written, Mr. Wright looked up.

“This is what we know,” he began. “For several months, according to Barney’s original explanation, when he gave me the case, airplane parts had been missed. Not very many, but some. We have to decide how they are taken, and then find out who does it and what happens to them, how they are disposed of.”

“How about the man who gives out the instruments and such?” asked Langley quickly. Bob thought he said it to forestall comment about Griff, “or the mechanics whom Al had been told by his rigger boss were possible culprits?”

“That point is not important,” Mr. Wright declared. “It is the beginning of what we know, and can wait. Our second bit of knowledge—and more important this is, too—is that for several months before the seemingly fatal crash, accidents had occurred to every airplane that was sent out of the plant. Buyers complained by letter, and only by good luck was it possible to avert several tragedies.”

“It had,” Barney nodded. “We wanted you three boys to start in with open minds. Remember? We didn’t tell you details; but now it’s gone too far for taking things easy. We’ve got to get to work.”

“Right,” agreed the detective. “The third point we know is that Mr. Tredway was very anxious to hold up the good name of his corporation, and that he decided to take this last ship to its owner in person, after Lang, here, gave it—” he paused, noticing Bob’s expression.

“I know what’s on your mind,” Langley said, turning to his younger cousin. “I was the one who tested and checked that Silver Flash. I said she was O.K. before the take-off. But,” his manner was defensive, “if you think——”

“I don’t think,” Bob asserted. “For a minute I did—but Mr.—but Barney says not a thing was wrong about the Silver Flash. So, of course, there’s nothing to think.”

“Besides,” said Barney, “we none of us knew it would be the Silver Flash. The buyer couldn’t make up his mind, till almost the last minute, about that pair of twins. One time he’d come and say he liked the silver, then he wanted the copper-gold finish. Both crates were identical except for that. I thought, myself, he was going to take—well, we all thought the last time he came he wanted the gold one. But I guess he telegraphed.”

“Well, then, that explains one thing,” said Bob. “If everybody thought he wanted the Golden Dart, that’s why the rudder rope was frayed off in that ship.” Barney, who had been told everything, nodded.

“Yes,” he admitted, “but that don’t explain why the other ship—sound and perfect—crashed. Unless——”

“Unless—what?” Bob, Lang and the detective were interested, but Bob voiced the question.

“I run the plant,” he said. “The deep part of the money end, and all that is none of my business. But I happen to know there’s some trouble about money, or losses, or something like that.”

“You think—” Mr. Wright bent forward, “—Tredway, because he was in some financial difficulty, or deeper trouble, might have done away with himself?”

“Well,” defensively Barney replied, “how else do you account for a diving ship, placed so careful, on the lakeside, close to shore, and only damaged as little as possible, and then not from anything being wrong in her?”

“They didn’t find hide nor hair of him, did they? Dredging, or searching didn’t locate anything!”

“However,” the detective objected, “that doesn’t explain about the frayed cable, or the other things done to airplanes to damage the reputation of the corporation; that is my theory about the motive.”

“No,” Barney admitted. “If you’ve got a theory about the motive for damage to crates, maybe you’ve got one about the whole affair.”

“There are three crimes to investigate,” Mr. Wright said slowly. “The accidents, the thefts, and the——”

“What sort of crime? Nothing is wrong with the ship he used, Barney says,” objected Bob.

“A very strange one,” his father replied. “Remember—there was a brown airplane hidden in a field. It was gone—before the accident. My theory is that either some one he feared, or some one who hated him, took off in that brown airplane, overtook or waited for Mr. Tredway—and——”

“Yes,” agreed the detective, “let’s drop all worry about the less important thefts, the deliberate damage to the airplanes—and look for the man who flew that brown airplane!”

CHAPTER XIV
THE SKY SQUAD DISOBEYS

Both Curt and Al listened eagerly while Bob related the details of the Sunday conference with the detective.

“Not a thing wrong with the Silver Flash?” repeated Al. “Then that brown crate must have driven it down—but why?”

“Maybe some revengeful pilot Mr. Tredway had discharged,” suggested Curt. “At any rate there must have been some motive to make a man do anything as terrible as that. But how are we going to locate the brown ship?”

“I still have that message we discovered on the seat, and then picked up in the dewy grass.” Al produced it, dry but smudged and crumpled, from his pocket card and identification case. “We might compare the writing with the—well, say with the books in the aircraft plant, and with everybody’s writing.”

“Lang didn’t get any information when we made inquiries about the brown craft at the nearest airport, did he?” Lang, who was quite affable and good-humored, with Griff and his actions forgotten in the new search, answered Curt.

“No, nothing more than you did. They’d never heard of the ship I described.”

“ You have got me more puzzled than this whole mystery has,” Al said, grinning. “Lang, the way Bob tells it, you must have been next door to ordering the undertaker, and then you were flying, stunting, as if you’d never eaten fish and ice-cream.”

“That’s psychologically explainable,” Lang liked to use long words, to indicate his superiority. “Under the stimulus of——”

“Never mind!” Al threw up his hands as if to ward off a flow of words too long for his youthful understanding.

“It’s too easy to explain,” Bob said. “Father said Lang got so excited that he forgot to think about himself, and ‘Nature took its course’ when he stopped worrying about his fears.”

“That was it,” agreed Lang. “I accepted the idea, from somewhere, that ice-cream and fish made poison, and while I was flying, when a little gas began to bother me I got scared, and the scare did the rest. Uncle said that half our pains are due to believing what other folks tell us can happen; the rest is from being afraid it is happening to us!”

“That clears it up.” Al became very sober. “I wish the disappearance of Mr. Tredway was as easy to settle.”

“Well, we’ll have to find that mysterious brown ’plane, or get hold of somebody who saw it flying, to tell us which way it went.” Lang rose, stretched, yawning, and sauntered off toward his wheel; the other three, sitting on the cottage porch before supper, for which Lang would not stay, looked after him in silence.

“Do you know what I think?” Curt broke the thoughtful pause. “I don’t mean to criticise, and I don’t want you fellows to get angry, but I have a feeling that Uncle Fred is wrong to have us drop all our suspicions and try to find a crate that could be five hundred miles away, in any direction. My theory is that if we locate the airplane it will be by ‘luck’ and I don’t believe in ‘luck’ because if you think ‘luck’ is going to help, you don’t have to do anything yourself, and if you believe it is going to hinder, there’s no use in doing anything. So,” he grinned, “I believe that everything comes out right only when we do everything we can to make it so—and as long as there isn’t any way to start hunting that brown crate, let’s——”

“Uncle Fred didn’t give you orders to ‘lay off’ watching, did he, Bob?” and as Bob shook his head, “He only meant for us to concentrate on seeing if we could pick up a clue to the mysterious ’plane. Well, I feel that by finding out what Griff is doing, and why his father is so fidgety and furtive, and the rest of the puzzles here, we may be led to that ’plane, or get a clue to it or to its pilot.”

“Well,” Curt answered Bob, “the way I look at it, if Uncle Fred took us into the case he expected us to obey the ‘spirit’ of the orders he gave, and he did say to forget the smaller things here and work on locating the ’plane.”

“I see,” agreed Bob. “It’s a pretty deep—what Lang would call, ethical problem. Father meant to leave Griff alone, unless he did something actually incriminating, and to put all our effort on the other thing. Let’s see your paper, Al.” He held out his hand for the brief note Al had preserved.

Study it as they would, they got nothing helpful from the grass-stained paper with the smudged writing.

“Let’s think who we’ve seen use an indelible pencil,” hinted Al. “Remember, the morning we found this, we decided, in a joke, that there were too many indelible pencils to try to trace the writer because he used one; but how many people close to this mystery have you seen using one?”

“Yes, Bob—because he takes a copy of every order he writes and of every requisition, on an old-fashioned letter press, the same way they put their copying ribbon letters in between a damp cloth and a soft, thin sheet of the big book, put it all in the press and make the copying ribbon print the letter into the book instead of using carbon paper!”

Each of the three having spoken in turn, by common consent they agreed to Al’s impulsive suggestion. They were hardly able to wait for their supper; however, they put it away with speed if not with the best of table manners and secured their bicycles.

The watchman accepted their explanation that they were passing and wanted to borrow several books from Mr. Tredway’s reference library, in the offices.

Bob, accordingly, went to the offices, while Curt and Al strolled, with apparent aimlessness, across the inner quadrangle.

“There’s a light in one window—no, in two windows—already!” Al mentioned. “I wonder who’s here, at night again.” Almost at once he suggested that they go and see.

They saw Bob, who had lighted the outer office electric bulbs, choosing several volumes from a shelf, to carry out in truth their explanation to the watchman.

“Now—who’s here?” Bob said, joining the others at the door as he put out the light.

“Can’t be Barney—unless he came back—no, the cabin ’plane isn’t here,” Al argued. “Anyway, Barney stayed over to transact some business, you said, Bob. Must be either——”

“Griff, or Griff and his father—or Mr. Parsons and somebody else,” Curt said breathlessly, excited. “There were two separate offices lighted, and you can see the door glass shining.”

“Yes,” continued Curt, “but one of us can hide in the alcove where the water cooler and door to the washroom are located. If anybody comes, it would be easy to dodge on into the washroom and no one would ask questions about that.”

“Then you’re elected!” Bob said. “I want to go with Al, because I think I know where to find the latest letter-book.”

With the reference volumes tucked under his arm he led Al down the dim corridor, while Curt secured a good place in the niche by the water cooler to watch from.

As the two brothers went down the steps, at the rear, toward the supply room, to be sure that no one was there and likely to come up and catch them, Al’s grip on Bob’s arm tightened convulsively.

He led Al down to the lowest steps, and there, just beside the door to the supply room the brothers flattened themselves against the wall.

They held their breath. They made themselves as small as they could. A quick tread came on down the steps, there was the pause of a body close—almost touching them. Breathing, sharp, short, quick, carried to their ears; but they kept mouse-still. The door opened.

A light flared up as Bob dragged Al back out of range. But as they turned and stared down, hearts still pounding from the excitement of the narrow escape, both brothers gasped.

CHAPTER XV
A TRIPLE TRAIL

Pulling Al further back out of the light, around the little dark jog beside the door jamb of the supply room, Bob put his lips close to his brother’s ear.

With a little squeeze to reassure his brother, Bob let go of Al’s arm and tiptoed back up the stairway, carefully clinging to the side wall and hoping that this precaution would enable him to get away without causing the steps to creak.

He was successful. Al, noting that the man inside the room seemed to be doing nothing more than standing there considering the layout of the place, guessed that Bob wanted to consult with Curt, watching upstairs. Al felt important: he was in the very heart of mystery, and much depended on him. Therefore he watched with every faculty alert as the man turned his head this way and that, apparently inspecting the stock of wing and fuselage cloth, the boxed instruments, the cases of “dope” for varnishing bodies and wings, the many other visible objects held in reserve.

Bob, slipping along the hallway at the top of the steps, noticed that both offices were lighted still, that both doors were closed, and as far as he could see, nothing had changed up above.

Curt was still watching. He was practically invisible in his nook by the water cooler. Bob, with a small word under his breath, reassured his comrade who came out of hiding as soon as he knew that the footsteps he heard approaching were Bob’s.

“Was he a stranger?” Curt asked. “I thought it was Mr. Parsons. He came out of that dark directors’ room, beyond me.”

“Oh!” Bob clutched Curt’s arm in a tight grip. “Have you used your eyes, Curt, in daylight? If you have, you recall that there is a fire escape running up the side of the building—and the landing is by that directors’ meeting room window.”

The opening of one of the lighted offices startled them, ended the consultation. Both comrades, tense, drew close against the wall behind the water cooler. If anybody was thirsty!——

The lighted square of that door went black. Someone had put out the dome light. Footsteps went carelessly along the corridor from the hiding youths, toward the front stairway.

“I must follow—whoever it is!” whispered Bob. “Curt, watch here. Al will watch that other man. It’s——”

Bob agreed and tiptoed along to the stairway. By the time he got there he had no need for special caution, the lower door was closing.

Bob ran lightly down the stairs, crossed the entry below, cautiously peered into the yard, lighter just there by the arc over the office building doorway, and nodded to himself.

Cautiously Bob trailed him, allowing the partner’s son to get out of sight beyond the turn before he left the doorway.

Where was Griff bound? The main gates were across the yard and, as Bob knew, they were locked while the night man made his rounds of inspection among hangars and plant structures.

While Al watched his man in the supply room, while Curt hid, watching the lighted office door, Bob wondered what Griff was about. The young man did not go anywhere near or bend his steps in the direction of the main entrance but turned, with Bob carefully watching as he clung close in the shadow of the office structure, and went on around the building toward the private exit used by the officials. Being the son of Mr. Tredway’s partner, Griff had a key; but Bob could see, as he peered around the building, that the gate stood slightly ajar already.

His thought was answered by Griff’s actions. He paused at the gate, seeming to inspect it. He was surprised to find it ajar, Bob decided. He held his place close to the office shadow and watched, as Griff looked around, inside and outside the fence.

Then, as though discovering something, Griff ran out of sight, leaving the gate as he had found it.

Instantly Bob ran across the small open space to the gate. There, in sudden caution, he cuddled his body close to the fence; it had just crossed his mind that Griff might have gone outside in a pretended hurry to draw out any pursuer; he might be hiding, watching!

“That’s queer,” Bob mused, while he projected his head through the gateway. Almost in the same instant that he saw Griff starting up a motorcycle, Bob saw Griff shut off the motor and trundle the machine away.

“His own motorcycle is broken, since Saturday’s accident,” Bob reflected. “Now he must have brought another one. He meant to ride off in a hurry,” he deduced, “but he decided the noise would startle and warn people, so he’s going further away before he starts up.”

Instantly his own action was decided upon. He streaked back across the yard, around the hangars, to get his own bicycle. Against a speedy motor it would not keep Griff in sight, but it would enable Bob to get over the ground faster, and, if Griff did not go home, Bob meant to pursue him, making careful inquiries as he pedaled. There was only the crossroad for him to take, and Bob could see it from the highway.

In a very short time, and without having been seen by the watchman, Bob was out on the road. The distant sputter of the motorcycle engine and a speeding form passing the junction of the crossroads gave Bob all the information he needed. Without wasting energy in an effort to keep the flying cycle in sight, he pedaled after it.

Al, watching, saw the man who was evidently making some notes in the supply room, suddenly dash to the switch. Out went the light.

Al heard the scrape and rumble of a window being unfastened and thrown up. The man was listening, he judged.

Curt, by the water cooler, heard nothing but the faint sounds of the motor; at first he thought they were shots. When he saw the office light go out suddenly, immediately afterward, he thought someone in there had shot at some one else; but the door was flung open and he heard hurried feet pounding along the hall and almost stumbling down the front steps, careless of how much noise they made.

Curt could not go to explain to Al. He must see who that was going out of the quickly darkened office so swiftly.

Al needed no one to warn him. He crouched, tense and listening intently, outside the supply room door for a full minute. Absolute, torturing silence began to twitch his nerves. Nameless fears and countless uncertainties filled his mind. Was the man stalking him? Was he there at all? Had he ever been there? Was he human—or——?

Al heard a queer sound; at once he identified it. The window was being quietly pulled down.

Curt, slipping down the banisters in the good, old-fashioned, speedy boys’ way, landed quietly at the foot of the stairs soon after the front doors of the office building closed.

But by that time whoever had emerged was far across the quadrangle and it was too dark to recognize him. There came the flare of the headlights of an automobile.

From its position on the grounds and from the style of its lamps, Curt guessed it was the runabout used by Mr. Parsons, Tredway’s remaining partner. What was he doing here? Where was he going? Curt, in the office doorway, not daring to emerge because of the beams of light that might swing around the yard at any moment, heard the voice of Parsons hailing the watchman, questioning him. The other replied in a way to show he had not heard any noises, could not account for them.

Curt, as the car got under way and the main gate was flung wide to permit it to depart, raced around the office building “ell” and across to his bicycle. He knew he could not pursue, but the wheel would give an excuse for emerging from that gate at once.

“Wait!” he called to the watchman, pedaling swiftly across to him. “I guess he forgot I was here,” pretending that Mr. Parsons sponsored his presence there so late at night. The watchman said nothing but held the gates open until Curt pedaled through and took his way after the car, not to keep it in sight but to see if it went to its owner’s home.

Al, ignorant that he was the only remaining member of the Sky Squad, watched tensely and listened alertly beside the supply room door. He heard nothing. Cautiously he protruded his head around the door jamb.

“But how—where—could he go?” Al answered his own questions at once, for the window, made of tiny panes of thick glass between heavy bars, locked always from inside, impossible to open from outside, was not tightly shut.

That window was not tightly shut. He had heard it opened, and—closed. But if the man had closed it from within the room he would have pulled it down tightly. He had not done so. He had left it partly open—why? To provide a way to come back, Al decided.

Almost at the same instant it flashed into his head that if he were to be caught in that room, with its door unfastened, he would be accused by any of the plant members, the watchman or those he thought were still in the upstairs offices, of stealing whatever might be missing.

He tiptoed back to the steps, listening. No sound came to him. Softly he went into the open doorway, made sure the window was not tightly shut, by inspecting the lighter space beneath it, then very quietly let the door go shut, allowing its spring lock to snap. He could open it from inside if he had to escape. No one without a key could open it from the hallway.

Then he ran close to the window, peered out, listened with an ear to the crack beneath the lower panes.

Nothing was stirring. But from the window he could see the gate, and the light was sufficient to show him a man’s form arriving there.

Evidently the form stopped from surprise or caution, then it went swiftly out. Al, forgetting fear, flung the window slightly upward, edged out, dropped to the ground, reached up and almost closed the window, then fully drew it down with a little slam, and raced to the gate. There he paused, peering out carefully.

CHAPTER XVI
THE “WINDSOCK”

For Al the trail ended abruptly after a walk of a mile. The stranger, whose face, with its heavy beard, Al could not dare get close enough to identify—even if he knew it!—hailed a passing automobile, asked for a “lift” and was taken in. That concluded Al’s chances of following because no other car came along. Dejectedly he returned to the aircraft plant to discover that some one, perhaps the watchman, had closed the gate. There was nothing left for him to do but to go to the main gate, call the attendant and get his bicycle. His friends were gone, the man assured him, and Al had no excuse to stay there.

Dejectedly, feeling that he had been close to a clue and that it had slipped through his hands by his “bad break,” Al rode home.

Curt’s trail took him, eventually, to the Parsons cottage. Seeing the car drawn up before the garage, Curt decided that he had no need to watch the car being put into the garage; evidently its driver had gone into his home for a moment first. Curt rode away. Had he waited his trail would have led further; but he did not guess that!

He saved his strength as he pedaled along, well ahead of his two less fortunate trailmates, and when he came to a cross street of the suburbs where a policeman was directing traffic Bob drew up beside the officer.

“Yes, Mr. O’Brien. I stayed at the plant—I’m learning how they put airplanes together at the Tredway plant. I wanted to ask if you noticed a motorcycle, not long ago—maybe fifteen minutes—a friend——”

“Yes,” the officer, starting the cars down the street by a wave of his hand, did not wait for an explanation of Bob’s reason for the question, “Griff Parsons rode by.”

Bob knew that Griff’s house was several blocks over, on an up-and-down street that was “one way” for traffic. If Griff had turned here Bob’s quest, he knew, was over; if he did not, Griff would be gone much further, because if he did not turn here, and thus enter his own home street in the right direction he surely would not go on and approach it in the wrong way, against the traffic rules.

“He rode on by, just waved to me,” O’Brien said, and turned to signal a warning to a car that was trying to slip past the stoplights.

The highway had no turns, except the suburb’s cross streets. It was possible that Griff might have turned into one of them, perhaps to return a hired motorcycle to its garage; nevertheless, so strange had been the action of the youth that Bob decided to ride on, at least to the last police officer along the main traffic road, to see if he could learn whether the trail continued or not.

The traffic officer, used to seeing this rider, greeted Bob and told him that several motorcycles had passed him. Bob, riding to the curb to rest, was puzzled. Had one of those been the motorcycle he had followed?

Griff, Bob knew, from his own inquiries, “hung out” with quite a rough crowd of youths; they had very little reputation in the suburb, and one of their haunts, near Rocky Lake, came to Bob’s mind. Griff, riding his motorcycle, might have gone on to the inn or roadhouse or “speakeasy” or whatever it was, near the picnic grounds at Rocky Lake.

On roadside signs, down the road in both directions, were admonitions to automobilists to “set down at The Windsock,” “Don’t fly past The Windsock,” and such tempting notices.

A windsock, Bob knew, was the cornucopia of doped cloth, closed at one end and held open at the other by a metal ring, which was fastened in a prominent, high position at every flying field and airport, to be filled by the draft of a breeze and thus, by its position, to indicate to flying craft which direction to “head in” or to “take off.” Since an airplane is much easier to get off the ground, and back to earth, headed into the wind, the “windsock” was a most important adjunct to every field; and Bob knew that the name, and the symbol, a real windsock on top of the inn, had been chosen by its owner because he had been an ex-pilot who put his money into the hotel venture and tried to attract picnickers, automobile parties and other patrons of a less savory nature by the novel idea of having his dining alcoves built to resemble the cozy little cabins of airplanes and had his meals served by girls clad in suits and helmets resembling those worn by pilots. Also, he had let it be rumored around town that he chose the flying symbol and the aviation idea because, in his inn, “the sky is the limit!”

Bob, approaching, was surprised to see the very motorcycle—he was sure of that!—he had followed, leaned against a post in the parking yard, and he felt certain that his long ride had not been wasted.

Where was Griff? Bob wondered. He hoped there would be some way for him to discover the whereabouts of the youth.

Not wishing to walk into the place for fear he might disclose his presence to Griff, Bob skirted the building, unobserved.

Bob did not need to get within sight of the occupants: he recognized Griff’s loud, sharp, furious tones. What was he saying?

“——all I could scrape together—I did put it in that package, I keep telling you——”

“If you don’t, you better say. If you don’t come through—by this time tomorrow night—I’ll ask your old man for it!”

Bob did not dare creep any closer. They might look out of the window. Some payment had been made, by Griff’s claim. By the denial of the other man it had not been made. By his threat it must be made.

Bob hesitated—and while he stood, undecided, the roar of a car, coming at full speed, came to his ears.

He glanced down the road. Hardly had he located the direction when he recognized the car. It contained—Mr. Parsons!

A man’s head leaned out of the open window. To Bob, as he crouched back into some ornamental shrubbery, the face was unfamiliar; but he saw it was brutish, fierce, angry—and he impressed it on his memory.

“Here’s your pop, now,” the man called—and then he gave an exclamation that Bob could not comprehend. Presently the light went out—and, almost at the same time, while Parsons alighted in the parking place, Bob, near the rear corner of the building, saw a form emerge from the kitchens and race away down the yard toward the grove beyond.

“Griff!” muttered Bob to himself. “Griff—running tight as he can go—running away from his father—to hide.”

Watching, more interested in the new arrival than in the son, Bob remained in concealment. But his mind was puzzled.

CHAPTER XVII
“THE CASE IS ‘SEWED UP’”

Sitting on the Wright porch, early the next morning, Curt and Al listened eagerly to Bob’s recital of the past night’s events.

“What could I do, except keep hidden and watch?” Curt’s question brought the counter-question from Bob. “The taxi door opened—and who do you suppose jumped out?”

“I saw him hail the taxi,” Al exclaimed. “Everything is beginning to fit together.”

“Yes, it is,” Bob agreed, “and, what’s more, it fits tightly. As soon as the stranger paid his fare he recognized Mr. Parsons who was halted on the roadhouse veranda, watching. They began to talk, and stood there for a minute.”

“They knew each other!” Curt exclaimed. “They must be working together to loot the supply room. That’s probably how the mystery man got in: he had a key from Mr. Parsons.”

“No—but the stranger saw his motorcycle. He got awfully excited about it and he went with Mr. Parsons to look at it. They went close to where I was hiding back of the shrubs, but they didn’t say anything until they were close to the motorcycle. They were too far away for me to hear, then.”

“Oh—yes! You would!” Bob was scornful. “Right out across an open yard!”

“They talked for about ten minutes—then the man made some notes of things Mr. Parsons said—I wish I could have heard! Then he hopped onto his motorcycle and rode off, and Mr. Parsons stood thinking for awhile and then——”

“No! He drove away. Griff must have been watching, too. He came out, and shook his fist toward the roadhouse and then walked off, and—that’s all.”

They discussed the incidents of the past night, coupling them with the strange actions and uneasiness of Mr. Parsons and of Griff on former occasions, riding, as they talked, toward the plant.

Barney’s cabin airplane was again on the field, and as soon as they arrived and he saw them, from an office window, Barney summoned them.

“Well,” he greeted them, closing the door, “how goes the study of airplane building?”

“Oh, we know how they lay down the framework for the fuselage and how careful they are to see that every longeron and brace and strut and guywire and turnbuckle fits exactly in place and is well fastened,” Al exclaimed. “And we’ve helped put on the wings and the tail assembly, and Bob is going to help install an engine, today, and we will watch.”

“It was just a ‘polite opening’,” Bob grinned. “Barney wants to know about—other things we’ve learned.”

“The partner and his son are working with an outsider. I thought so. But what about the brown ’plane? Any news of that?”

“We disobeyed Uncle,” Curt admitted. “Bob said Uncle wanted us to drop things here and concentrate on trying to find the brown ’plane, but——”

“Not only that, but if a crime is being committed under your nose you won’t go off looking for something else to do while it is going on, will you?” Al wanted their course confirmed.

“You did just right,” Barney commended them. “You lads stick to this end of it. I’ve suspected that Parsons and his son were ‘up to’ something, and I don’t agree with your father, Bob, about the brown crate at all! I think you fellows deserve a ‘raise’ and if you can only catch one or all of the crowd doing something—catch them ‘red-handed’ in a way of speaking, I’ll hand out a little private reward. I feel that it’s due to—to the memory of Mr. Tredway. He was mighty good to me and—and I want to—get everything cleared up here, because I think the ones who have been doing wrong right here at the plant got found out by him and they either hired that airplane from some distant place and flew out and rode down Tredway or else they paid some unscrupulous pilot——”

“Unscrupulous pilot!” reiterated Al. “Why—the man at The Windsock is a—an ex-pilot.”

“Well, from what I saw of him, his face shows that he’s unscrupulous,” added Bob.

“It looks to me, from here,” Barney said, slowly, “it looks to me as though we’ve got the case ‘sewed up.’ All you need to do is to find out, some way, about that ex-pilot—what he does with his time, if he owns a crate yet, and so on.”

“I think,” he nodded, “that ex-pilot might know a lot about a brown ’plane, and about what it did to force another one down——”

“Then we have got the case ‘sewed up’,” Al declared. “We came here last night to see if we could compare a little scrap of writing we found where the ‘plane had been, with the books of letters and things to see if the writing agreed.”

“We had no time to find anything,” Curt admitted. “The other things came up——”

“Well,” said Curt, “it’s done with an indelible pencil. Now that we know the ex-pilot is under suspicion, we can find out if he has an indelible pencil that he carries around—or, he might destroy it, considering what has happened since the note was written.”

“But who’s the note written to?” asked Bob. “It says ‘everything O.K.’”

“We ought to get a sample of the ex-pilot’s handwriting,” suggested Al, eagerly. “Shall I? I can try! They don’t know me out at The Windsock. Couldn’t I take my autograph album—and——”

“I’ll make inquiries about the brown ‘plane, from around The Windsock,” added Curt.

“Fine!” agreed Barney. “Fine! Yes, sir! Boys—we’ve got the case ‘sewed up’ or circumstantial evidence never pointed true.”

“Yes, but he’s awfully busy on that other case. He must trust you fellows pretty well.”

“Well,” Al swelled with pride, “maybe we’ve disobeyed orders, but if this comes out as good as we think it will, we’ll have no trouble making Father see that he was wrong and we were right to disobey.”

Griff seemed to be getting ready to work himself into danger for their special benefit, it seemed to Bob in the engine assembling rooms. The youth was angry, upset, uneasy, fidgety; he hurried out when he heard his father’s voice approaching down the hall and the older man betrayed as much uneasiness and concern as did his son.

But that night, when they thought they had the last stitches taken to “sew up” the case, as Barney said, Fate ripped out the whole thing—and they were left without a thread of a clue!—until the unexpected thing happened that gave Bob his “hunch!”

CHAPTER XVIII
A NEW MYSTERY

“Barney—Mr. Horton—” he corrected his own familiar allusion to the manager of the aircraft plant, “—says please hurry the work on this sport biplane. The man who’s buying it is in a big hurry. He wants to get into some race with it.”

“Oh, sure!” the rigger grumbled a little. “They’re all in a hurry. But I don’t rush my part of it for anybody. There’s been enough complaint about this plant, already, without me doing anything to cut down the performance of a crate by skimping my share of the high standards Mr. Tredway always kept up.”

“Yes,” the rigger was in a complaining mood, “that’s all very well. But did he say why they’re giving us cheaper stuff to work with, since the real boss—went West, maybe!—did they tell you why that is, that we’re getting cheaper stuff!”

“No,” Al admitted, “but I do know that Mr. Parsons and Bar—and Mr. Horton were talking about some complaint from the wing assembling room, about poor fabric. They almost quarreled. Barney told Mr. Parsons it had to stop, he was going to uphold Mr. Tredway’s ideas, and Mr. Parsons said so was he.”

He picked up a turnbuckle, a metal object in which the threads of each wire end were so threaded in that when the ends of wires were screwed in, the turning of the central, revolving part either drew the two sections of wire close, making it taut, or allowed them to recede a little from one another, for more looseness—by which the flying and landing wires, and other parts of the guying rig were adjusted.

“Shows how much you know,” scoffed the rigger, Sandy. “Look here—heft this—and then this one!”

He selected another turnbuckle, handed both to Al, and the youth “weighted them” in his two hands.

“Of course it does! It’s a cheap casting, not the aluminum alloy the other one is machined from. Why, them threads on the new one will wear and go bad in no time!”

Al, watching, observed that as the rigger manipulated a pocket knife in the threaded end of the part, bright metal and a worn look were almost immediately evident.

“Yes,” Sandy Jim agreed with his discovery, “and I’ve been talking around and others is dissatisfied—in the dope room, in the engine room. Everywheres!”

“But when Mr. Parsons talked with the manager,” Al explained, “they had the supply clerk in and went over the orders and way-bills and delivery check-up, and everything was all right. The orders went to the same firms, as always——”

“We’re getting shoddy stuff, all the same!” grunted Jim. “What good is it to rush out a ‘job’ and have it accepted on the reputation of Mr. Tredway, and then have complaints in a few days?”

“I don’t know,” said Al, and changed the subject. “Mr. Horton says you’ll have to excuse me, this morning. He’s sending me out on an errand.”

“Oh, sure!” Jim snapped. “Wants this job rushed, and takes away my helper! Whyn’t he use his office boy?”

Al could not explain that it was Barney’s way of releasing him so he could go to The Windsock for that comparison of the ex-pilot’s autograph with the clue note Al held.

“I guess you’ll have to ask him,” Al grinned, and went over to get his bicycle. Sandy Jim followed him, dragging a small parcel out of his hip pocket.

“As long as you’re riding,” he suggested, “go past the house and slip this in to Jimmy-junior. It’s some odds and ends of broken stuff for him to use on his new model air-liner.”

Al quickly sent his bicycle along the highway. Stopping at Sandy’s home he took as little time as he could to drop the parcel, and to explain to Jimmy-junior that the reason he had not yet been taken into the Sky Squad was that they had been too busy, evenings, to hold any meetings.

Then he made his way to the roadhouse near Rocky Lake Park, and leaned his wheel against the veranda supports.

“Is Mister Jones busy?” he asked a sleepy waiter who was listlessly dusting off some chairs in one of the small compartments made to look like the cabin of an air-liner. Al had found it easy to learn the ex-pilot’s name.

“In the office,” the man jerked a thumb toward a side room. Al, knocking at the door and hearing a gruff voice bid him enter, went into the same room Bob had described as the scene of the quarrel between the roadhouse man and Griff.

The man, looking up from some work at a small desk, had a coarse, scowling face. No wonder he was “ex” pilot, Al reflected, with a face as brutish and a manner as unfriendly and curt as “Mr. Jones” showed.

“Why—er—” Al stammered, not so much ill at ease as trying to pretend he felt shy in the presence of a great man, “I’m one of the fellows who have a sort of club, to study airplanes, and all that—and I—we—heard about you being a clever pilot, and I thought I’d ride out and ask if you’d be generous enough to write a little something about aviation in our club autograph album.” He produced the small book he had brought in his coat pocket.

He took the small volume and Al’s heart sank. Instead of writing sensibly and generously on blank page invitingly offered, he flipped the pages, and Al knew that the affair was a failure. There was nothing about aviation in the few autographed verses and sayings already collected.

“That’s no aviation album!” The man thrust it away angrily and jumped up. “What’s your scheme, young fellow?”

“Scheme?” Al tried to look innocent. “I told you—we want to get you to start the real autographs from aviators!”

The subterfuge did not satisfy the man. He frowned, stared at Al as though trying to get through his guard, to discover any hidden motive. Al, inexperienced, fidgeted, unable to conceal his uneasiness.

“Sure!” The man snatched up the book. “Come to think of it, why not? Fact is, kid, I’ll start you off with two autographs. Wait!”

He hurried out of the office. Al did not dare “peek” to see where he went or what he did. For all Al knew, the man might be just beyond the side door, watching. He sat very still, trying to be as self-possessed as he could.

“Here y’are!” he said, affably. Al, glancing at the book, saw that two opposite pages bore fresh scrawls. The man waved a hand. “Welcome. Run along, now. We’re busy, here—getting set to open up a new ‘airport’ out on the side, where folks can dance to a fine orchestra in a hangar. Tell any of your friends you like—especially your parents. We got the prettiest imitation of an airplane for the orchestra to set in——”

Al, hardly able to mumble his thanks, dashed out to his bicycle. He could scarcely hold in his impatience. One of those sets of rough characters was written with a pencil, the other with an indelible pencil!

A little way down the road, near the lake, where the airplane had cracked up, Al drew his machine in under a tree, almost tore the book out of his pocket and opened it hastily.

“Knowing when to stay on the ground makes a better pilot than knowing how to get off it!” It was signed with initials—“T. J.” Al did not recognize the writing although, he understood that the saying meant that a pilot wise enough to be cautious was better than one who thought that getting into the air was all there was to flying.

The second page revealed one word, the pilot’s good-luck wish, and two initials also:

Who had written the autograph? Had Mr. Jones? If his name was Jones he would have signed the initials on the first autograph—“T. J.” Or—would he have signed that way? Might he not have signed the reverse? Had he written either page? Who else had helped?

CHAPTER XIX
TANGLED THREADS

On a former occasion Bob had related news to an audience composed of Al and Curt.

As the trio rode homeward, Curt to share supper with the brothers, Al was the spokesman.

“Did you ever see so many people to suspect and so many clues that don’t lead anywhere?” asked Curt when Al had told his story and had shown his evidence.

“The Sky Squad has a mystery, and there’s no mistake about it,” declared Al. “We got what we wanted, but now—what can we do with it?”

“Well, it proves one thing, anyway,” Bob asserted. “The single word matches our ‘Everything O.K.’ note. That proves that the man who wrote the note is at that roadhouse, The Windsock.”

“It does,” Curt agreed. “But—is it the man named Jones? Did he write it?”

“What does all that matter?” Bob said. “The point is that we have proof that the man who used the brown ‘plane is staying at The Windsock. Now our job is to discover who he is.”

“Let’s see those autographs again.” Curt drew his wheel to the roadside and took the book from Al. “‘T. J.’ is written with a plain leadpencil,” he remarked. “The ‘J. T.’ one is the one written in indelible pencil. ‘J. T.’” he repeated thoughtfully. “Do you suppose Jones transposed his initials and then got a waiter or a clerk to write the other and sign what Al would take for his initials?”

“It’s too tangled up to suppose about,” argued Bob. “Two things we do know from it.”

“One is,” Al remarked, as they resumed their ride, “one is that we know the brown airplane man is at The Windsock. What’s the other?”

“Well, whether it’s Jones or not—Jones has something to hide, this proves. Otherwise he’d have scribbled a word or two for Al, and thought no more about it.”

“It simplifies things, doesn’t it?” Al, speaking after Curt’s agreement, was not so sure as his words indicated.

“It makes them more complicated,” Bob retorted. “Let’s see what we know and where we stand.”

As they rode slowly, he tabulated their clues and theories and discoveries, with many interruptions from his companions.

“First of all,” he began, “we saw a mysterious brown airplane hidden in the woods. Then, when we went there, it was gone—and this note was flung aside. The crate took off in a hurry because we saw heavy tracks, and made in a hurry, by the way they looked. Then there was a crack-up at Rocky Lake and we found out Mr. Tredway was in the Silver Flash that crashed.”

“And we saw a man come to try to help, swimming across the lake,” Curt broke in.

“And then we met Barney and he and Father called us in to help solve the Mystery Crash,” added Al.

“We learned there was more mystery than just the fall of the crate,” Bob went on. “That was bad enough; but there was more! Parts were being stolen from the aircraft plant, and ‘planes had been tampered with—after tests showed them to be perfect!—and——”

“When we went there to work in the plant,” Curt was eager to add his contribution to the sum of their recollections. “We saw Mr. Parsons acting suspiciously, and Griff, too.”

“And we have suspected Langley was in bad company with Griff, and Lang got mad at us about Griff—but we haven’t found any reason to suspect Lang, since,” Al declared. “But now we’ve got more people to suspect—the stranger who came to the plant and this ex-pilot.”

“But all this hasn’t brought us any closer to knowing anything definite,” Bob objected. “I begin to wonder if Father was right, after all, when he told us to ‘drop those unimportant things and locate that brown airplane.’”

“But we can’t!” defended Al. “There’s no way to start hunting. I’m for keeping on disobeying until something happens to help us.”

“And I’m for getting in to supper,” Curt changed the subject as they dismounted at the cottage. “Let’s give what brains we have a good rest while we eat.”

“Well, one thing more and we will.” Bob paused, thoughtful and serious. “Al said we had no cause to suspect Lang. Well—today, I was wondering why Griff was so nervous and fidgety and furtive, and Lang came in and took me out, to give me a lesson in handling the controls, he hinted. He really did, but before he took me up while he tested the new sport speedster, he said, ‘I see you’re bothering Griff again,’ and he gave me ‘down the banks’ about it.”

“Not that, so much. But—he told me to go on home, that it was closing time, and I put on my cap and punched the time-clock, and then I recalled that I had left the baseball we were playing ‘catch’ with at noon, in my bench drawer. I went back, and there was Griff, all excited, and Lang, with his head close to Griff’s, acting as upset and as uneasy as Griff when I came in and surprised them. Lang snapped at me—I—don’t—like it——”

“Well,” Curt was quiet, a little hesitant, but firm. “If Lang is mixed up in something wrong—we ought to—at least we ought to try to save him!”

“That’s good,” agreed Bob, quickly. “I thought you were going to say ‘we ought to catch him with the rest.’”

As they sat at the table Al mentioned the morning’s chat with Jimmy-junior, and suggested that they really ought to go and spend an evening with him as he had urged them to do; if the others liked him, they could communicate by nods and take him into the Sky Squad, not as a full member, but just to please him and have a fourth member to call on if an emergency arose where he would be needed. Al vouched for his innocence and good nature, eagerness to please and willingness to work without asking for explanations of why he did a certain thing.

“He’d be a good one to send to watch anybody—Griff, or the ex-pilot,” Al spoke as the trio rode toward Jimmy-junior’s home.

Bob did not finish. He applied his coaster brake, made a quick signal for silence, swerved into a garage driveway, followed by his companions, and dismounted, dropping his bicycle on the lawn.

“Wonder where he’s going.” Curt slipped along the side of the house by which they had stopped. “He’s in a terrible hurry,” he reported, coming back. “In a second he’ll be passing this house. Get back—behind the house. I don’t think he’ll notice the bikes on the grass in the dusk.”

They hid from the view of anyone on the sidewalk. Peering cautiously out in turn they saw Langley hurrying by.

Al was correct in his guess. As they trundled their bicycles, keeping as far behind Lang as they thought necessary, they saw him turn in at Griff’s gate. Five minutes later, from carefully chosen points of concealment they saw Lang come out, take Griff’s repaired motorcycle and ride off in haste.

Consulting one another with dismayed eyes, the chums, by common consent, mounted and pedaled for dear life along the street, around the corner, back to the main highway.

CHAPTER XX
A PACKAGE OF MONEY

Before they reached the aircraft plant toward which they pedaled with all their power, Bob, Curt and Al saw a light flare up.

“There’s nobody at the gate,” Curt called. They were near enough to see the open gateway.

Bob slowed up his pedals, permitting the bicycle to coast along as the modern, free-wheeling automobile runs when the foot is removed from the accelerator pedal. Curt caught up to him. In a moment, as they approached the gate, Al came up also.

“Don’t let him see you at all,” warned Curt. “Better wait and ask the watchman after he’s gone. You’ll find out more, that way.”

They hid the bicycles, in case it turned out that Lang had not left the ground. Careful not to disclose themselves, they watched at the gate as the engine of the sport model owned by Griff was warmed up. In the flood of light on the runway they recognized Lang as the pilot, and watched him adjust flying helmet and leather jacket, get into the craft, test the instruments, checking carefully, and then get his wind direction from the windsock, which told that the light Summer breeze was from the South. The watchman swung the tail around, set the chocks again for a final test. Lang “gave her the gun,” to see if everything was hitting perfectly, signaled for the chocks to be removed, and since his craft was correctly headed into the wind the airplane taxied, gaining speed, and rose swiftly into the dark.

Hardly waiting for the flood to be extinguished, the trio of amateur detectives hailed the watchman.

“Too late to see Lang take off,” greeted Bob. “He didn’t say why he hopped at night did he?”

“Thanks,” Bob spoke to the watchman. “As long as we’re here,” he turned to his chums. “Let’s bring in our bikes and get some more of those books on metal alloys Barney told us about.”

“His office is lighted,” Al commented. “Let’s stop in and tell him about the note and the autograph.”

“I’m trying to check up on the firm’s books.” Barney waved a hand toward the pile of heavy volumes, ledgers, daybooks, indexes and others, scattered on his desk. “I can’t find out what way they’re doing it, but something’s being ‘worked’ about the materials.”

“Well, I can’t find it,” he pushed three of the smaller books into a large lower desk drawer, and turned, mysteriously smiling. “How do you like this idea?” he asked. “I’ll put a few books aside, and then, when the staff comes in, tomorrow, I’ll see how the bookkeeper and Parsons take it. If there’s anything ‘flim-flammy’ about them, they will show it when they miss the books.”

“Why—nothing special,” said Bob. “We thought if Lang was flying over to see Father, that would take him about three hours—or four, and he wouldn’t get back here before morning, so there’s no use waiting for him to come back here. But—we haven’t anything special to do, except go to call on Sandy’s son, Jimmy-junior.”

“Why not ‘stick around’ here?” suggested Barney. “For awhile, at least. I don’t want to be mixed up in anything, but if anybody should come slinking around, I’d like to know it—as long as you have nothing much on hand?”

“Why not put out all the lights, and just hang around in the dark for an hour?” suggested Barney.

They agreed readily enough, and felt quite like conspirators or real sleuths on a big case as they occupied easy chairs in the big “directors’ room” and talked in low tones.

Footsteps, sounding without effort at concealment, in the corridor, caused all three comrades to become tense and alert.

Bob felt a hand clutch his arm, and almost called out in his nervous reaction until he realized that Curt was whispering:

However, hardly had they gotten into concealment when they realized that there was no need to hide; the steps went briskly past the door and on, down the hallway.

At the door to the hall Curt turned, waiting until the other two joined him, he spoke quietly.

“You wait here,” he urged. “I’m lightest—and quickest, I think. Let me go on down and ‘snoop’ a little. He slammed the door so hard it jumped open a little—it’s Barney’s office!”

“Barney? He—do you suppose?—” Al was puzzled. “He told us to wait, though——”

Curt was gone, tiptoeing, clinging close to the inner wall, where, he felt sure, the boards were so sturdy and well secured that they would be unlikely to creak.

They waited, uncertain what to do—in fact, there was nothing they could do but wait.

They had only a moment to decide. Down the hall, from the stairway, came other steps; the chums drew back inside the doorway. They let Curt peer out.

“It’s Griff, this time!” he informed the others. “He’s coming to meet his—no he isn’t! Get back! Hide!”

Hesitating steps paused but before there was any further movement Curt, Al and Bob were well screened from any but a careful search in full light.

They were glad, this time, they had gotten under cover. Griff did not go to meet his father!

Instead he came into the directors’ room, at least as far as inside its door, where, a faint blotch against a very dull oblong of weak light, Bob saw him standing, watchful.

“Shucks!” thought Al, “we can’t find out about Mr. Parsons on account of——”

They did not hear anything; but evidently the youth watching at the door did, for he came further into the room. Would he decide to hide? Might he choose the spot already occupied by one of the youths?

Their suspense was relieved! He waited inside the doorway, and it was a wait of a long, dragging three or four minutes that seemed like an age to the crouching trio; but finally he walked out, his step confident and loud, showing that need for concealment was over.

Quickly the three reached the door. Already, as they peered out, a light was glowing, but not electric ceiling domes—it was a pocket flash held close to something in Mr. Parsons’ own office.

Like shadows the three, arms touching, went down the hall. They could not contain their suspense. At an open door, partly drawn shut but not locked, they stopped. Looking through the crack, hardly daring to breathe or move, they saw Griff fit a key to his father’s desk, open it, take something from a small drawer—and walk confidently, if slowly, to—the safe in the corner!

Before it his light was held low, close. He was manipulating the knobs of the combination. As the partner’s son he had access to it, the chums realized. They forgot some of their caution but not all; they peered closely in through the crack of the door—and saw——

CHAPTER XXI
CAUGHT AND CLEARED!

Spellbound the three watching youths saw Griff count the bills in that packet he had taken from the aircraft plant safe.

They heard the ruffle of paper as he ran through the ends of the crisp, new bills.

With unexpected promptness, startling his companions, Al flung the door inward so that it banged against the wall. Instantly he leaped into the room. His chums followed. Startled, dropping his packet, Griff swung around to stare in amazement and terror.

“Drop those bills!” Al cried needlessly, “we’ve caught you red-handed!”

Al dashed across to the window, to block any possibility of Griff trying to drop the ten or fifteen feet to the ground. Bob snatched up the money. Curt blocked the door.

After his first look of stunned horror, Griff sank into the swivel chair and buried his face in his hands. His shoulders shook with a sudden revulsion of feeling that unmanned him, made him sob like a creature in pain.

For a moment no one moved. The comrades were rather dismayed and nonplussed by Griff’s pathetic attitude.

They had caught him, yes! Red-handed, as Al had said, they had caught him, in the act of something very dreadful.

Nevertheless, his surprising way of giving in, sitting there in a bent posture, with his body racked by his sobs, made him a rather pitiful figure.

“Stop that!” Bob said, finally, and rather gruffly. “You’ve done wrong. You’ve been caught. Take it like a man!”

“Yes,” Griff replied in a shaking voice. “Yes—I’m caught. I know I’m a baby—but—but——”

“But—what?” demanded Curt. “I suppose you’ll say you were forced to do this by somebody else. They always do, in books!”

“Oh!” Griff had hard work not to break down again. In spite of the way they had found him, in spite of what he had been planning to do, there was something that touched the youthful hearts of the trio, in Griff’s sorrowful eyes and drawn face.

“Oh!” he repeated, “if only somebody could help me instead of hounding me and——”

“We’re not ‘hounding’ you,” Bob defended their action. “You’d have done the same.”

“But you’ve been watching me and following me and suspecting me,” Griff declared sadly. “I know I deserve it—but——”

“Oh! Stop saying but!” Curt was annoyed by what he took to be an attempt to win sympathy. “We’d have helped you, instead of ‘hounding’ you if you’d been honest, instead of trying to be cunning and in with the wrong sort of people.”

“Nobody helps me,” responded Griff. “Everybody is after me for one reason or another.”

“That’s because you’re so furtive and fidgety that you ask for it—and doing things—like this—” Bob shook the bills.

Griff sat in silence for a moment. Bob walked over to the open safe, saw where the package belonged, and pushed it into place, then slammed the safe door, turned the knob of the combination to lock it and swung back to Griff.

“I mean this!” Bob came and stood in front of him. “I mean that the money is back in the safe. If you can show any reason besides temptation or somebody forcing you to do—this!—we’ll all promise to say nothing more about the things we saw you do.”

“That wouldn’t do any good,” he said despondently. “I’ve got to have that money. You think it’s—” he could not bring out the word, but he saw that the trio recognized what he meant. “It isn’t—because Lang is flying, right now, to his uncle, to get him to come back and give me money—a loan—to replace this.”

“Yes,” Griff answered Al. “It’s—it’s all mixed up and—awful!—but you say you’d help instead of telling on me, if I could show I wasn’t as bad as you think.”

Bob thought he saw a genuine honesty in the clear look Griff gave him. His sympathy was really quick and he wanted to be fair.

“Really we would!” Al was also touched; Griff, caught and breaking down and seeming to be declaring innocence in some way, was not the furtive, uneasy, shifty-eyed Griff they had known. “Honestly! Try us and see.” He and Curt moved closer. The three stood in a group in front of the huddling youth in the swivel chair.

“It will make me out bad enough,” he stated. “But—not as bad as you’ve been thinking. Oh, I know!” he took on a touch of his old defiance, “I know you’ve tried to connect me with all the wrong things that have been going on here! I know I’ve acted as though I am guilty. I’m not, though—not in the way you think.”

“All right,” Curt admitted. “We’ll listen. We’d rather have you innocent than guilty—of anything!”

“I guess you all think you’re clever,” he said, forgetting his own trouble for a second or two. “You come here to learn all about this mystery of where the missing parts go and who did things to the crates, and why. Don’t you think we have eyes? It’s all over the plant what you are trying to do. Don’t you suppose we all know one of you is a close friend of the other two, and Bob and Al are sons of a detective? What’s the answer?”

“The answer seems to be that you thought we weren’t smart and so you went right ahead.” Curt was a little nettled by Griff’s statement, although common sense told him, now that Griff mentioned the point, that their scheme must be fairly evident to any sensible person.

“I didn’t think whether you were smart or dumb,” Griff replied. “I had too much on my mind. Bad as it is, it might as well be confessed. I gamble, and owe money for it, and I came here to borrow this from the safe—it’s as much my father’s as anybody’s, because he’s Mr. Tredway’s partner, but—I didn’t intend to try to ‘get away’ with the money. I only wanted it overnight. Before the office opens Lang will be back with the money to replace it.”

“What makes it so important to get money at this time of night?” demanded Curt, suspiciously.

“I’ve been running around with a pretty rough crowd,” he admitted, “and they got me in the habit of going to places like The Windsock, out on the——”

“All right. There’s ways to gamble, out there, if you know the people who run the place.”

“Well—he owns it, yes. Mostly its Jenks, his manager, and the waiters that let the crowd do things outside the actual license rights of the roadhouse. Well, anyhow, I got to spending money pretty fast and I gambled. After awhile I lost so much I found out I was owing the ‘house’ as they say, more than two hundred dollars!”

Although several maxims and Biblical quotations sprang into Bob’s mind, he kept silent. This was no time for preaching, for pretending the “holier than thou” pose. Under the same temptations, argued Bob to himself, it would be hard to say whether he’d go Griff’s way or not. It isn’t how good a fellow thinks he is, but how good he proves himself to be under temptation, that counts, Bob decided.

“That’s what you’re taking the money for—or trying to,” Curt determined. “But why did you have to take it this way, and at this time?”

“The manager at the roadhouse said, last week, he’d have to get all the debts owed the house and clean up, because they’re spending a lot on a new dance place, like a——”

“Hangar. We know. Never mind why they wanted it. Tell me,” Bob changed the subject for a moment, “what does the owner look like? Is he short, thick-set——”

“Never mind,” said Curt, pacifically, wishing to get Griff’s side of the matter first. “We wanted a specimen of his handwriting——”

“I wish I could get one!” declared Griff, ruefully. “That’s the whole trouble, fellows.” His manner was more eager, more confidential. “I paid the money once—and he didn’t give me a receipt——”

“Oh!” Bob was connecting some things in his mind. “He came here one evening and demanded the money, and you gave him a parcel and then realized he didn’t give you a receipt. You tried to chase him on your motorcycle and got into an accident.”

“I thought you were watching, but I was too excited and upset to care,” agreed Griff. “Yes, I had borrowed from all the fellows I knew, and had scraped every cent out of my savings account, and I had the money. But he didn’t give any receipt, and when I finally got over the smash of the motorcycle and went to ask for it he declared I’d paid him with a package of wadded, folded paper and not money!”

“But it was money,” declared Bob. “Unless you changed it, because I caught you wrapping up something green the day I came into the engine assembling room.”

“It was money, all right enough,” Griff asserted. “But he wanted it twice. Well, I had promised my father that I wouldn’t go with that crowd any more, and I had been weak and went against my promise. So I couldn’t go to him about it.”

“If you had, and made a clean breast of it, he would have gotten you out of this scrape.” Bob had to say that much.

“I don’t think so!” Griff was morose. “He’s got so much worry on his mind about the plant and all that’s happened that he’s jumpy and nervous and suspicious and he’d throw me out of here, and maybe send me away from home. And I am trying to go straight. I will—I make a vow on that!—if once I can get out of this scrape. I’ve learned a lesson.”

“But that fellow at the roadhouse knows you’re afraid of your dad, I guess,” asserted Curt.

“I overheard that,” Al stated, and related what he had heard through the open office window at The Windsock.

“You fellows have been on the job!” There was a note of admiration in Griff’s voice, then he sobered and went on. “Yes, that fellow, out there, knows about me being afraid of Father, and he said if I didn’t have the money tonight, before midnight, he’d tell my ‘old man’ as he calls Dad. They’re opening a dance place and he said the cash was essential tonight.”

“Yes, and he’s going to call me, long distance, as soon as he gets there, and I was getting the money out so I could start for The Windsock the minute he calls up.”

“That explains everything,” he stated, almost regretfully. “Griff has cleared himself, and his father’s motive is logical.”

“It leaves us ‘up in the air’—and not in any ‘crate’ either!” agreed Al.

“Yes,” nodded Bob. “Barney said the case was all sewed up—but the threads must have been weak, because here’s our case all torn apart!”

Since Griff and Mr. Parsons were cleared of suspicion, the other two agreed promptly.

“I may be cleared,” said Griff sadly, “but I’m not out of trouble. If I don’t get this money to that man—Jenks is what we all call him, Toby Jenks!—why, he’ll call up Dad—and then——”

“Let me take the money out there!” urged Griff. “Just keep quiet about catching me here——”

“Even if the money belonged to your father, which the stockholders of the corporation might argue out with you,” said Bob seriously, “taking it, just overnight, would be—wrong, to say the least.”

“Yes,” admitted Al, “I guess it would be better not to worry him about this, if we could see how to get around it and still not let you take this money.”

“We suspected him,” Curt said, rather ashamed but anxious to be as frank as Griff, whose manner and actions convinced them that he had been absolutely honest with them. “We suspected him of being mixed up in something.”

“Everybody suspects everybody else,” admitted Griff. “Dad suspects Barney, Barney suspects me, I suspect the supply clerk and the bookkeeper of working together to get cheaper supplies here, and they suspect each other and everybody else—even you three!”

“Well,” Bob waved the statement aside, “that isn’t getting down to brass tacks. Think, for five minutes, everybody. We’ve got to help Griff!”

Seeing their case destroyed, their chief suspect cleared, they turned loyally to help to retrieve themselves by aiding him.

CHAPTER XXII
THE “MYSTERY CRATE”

“Father ordered us to drop this part of things,” said Al finally, “but I’m glad we disobeyed if it helps Griff to get out of trouble.”

“So am I,” admitted Bob. “But that isn’t what we were quiet for, to talk about what we’ve done.”

“That’s what I was coming to,” defended Al. “Let Griff stay here with you, Bob, while Curt and I ride out to The Windsock. We can call up as soon as we arrive, and then wait outside, hiding. Then Griff can take this money and come out, and pay it, and then we will jump in from outside the door and grab it and jump through the window and——”

“That’s you, all the way!” his brother challenged. “Quick on the trigger and sorry when the bullet hits the wrong target.”

“I have a plan, though,” suggested Curt. “Al and I can go out to The Windsock, as Al said, to get a good place under that office window. Then, when Griff pays the money, we will be witnesses, and if the man tries not to give a receipt we’ll be on Griff’s side.”

“I suppose the head Sleuth of the Sky Squad has the one perfect plan!” Al was sarcastic.

“No,” Bob was honest, “I haven’t! I thought of having Griff call the man and say he’d be there bright and early with the money——”

“I did tell him that, when Lang left. He said it would be tonight, whether he got it from me or from my father.”

“If we could keep that Jenks man so busy, keep his mind so much occupied he’d be too excited to think about Griff—” Al was not very sure of himself.

“We could!” Curt astonished Al by accepting the idea. “Look here! If he isn’t the ex-pilot, maybe the ex-pilot wrote that other autograph. Whether he did not or did, anyhow the Jenks man had something to conceal, or he wouldn’t have gone to the trouble of giving Al two specimens of writing to get mixed up with. Now—if we were out there, and Griff tried once more to stave off payment till morning, if he agreed, all right, we could come home and this money in the safe would be all right.”

“All right. If the man refused to wait, we could telephone in to Griff to find out, and if Jenks refused to wait, we’d walk in on that Jenks fellow and say we knew he was mixed up in something wrong about the airplane crash, and throw out hints, and so on. I think, myself, he is in it somehow. He’d bluster, maybe, but if he has anything to conceal, we could scare him, and then tell him to let Griff alone for the present or tell his story to a policeman—and we might hint that he could explain a lot about the crash——”

“I like it as well as anything you’ve suggested,” said Griff. “If you could ‘get way with it.’”

“Trust us to scare him good and proper!” declared Al. “I’d ask him ‘how about the brown ‘plane’——”

“No good,” argued Bob. “We looked that craft up in the official registry and she’s from out West, and while we know her markings we haven’t found her and I don’t believe he——”

“I do,” Al defended his deduction. “I think he had it brought here for him to use, and then taken away again, and that accounts for his note—‘Everything O.K.’ when the pilot left it there and he put the note on the seat to show he had been there!”

“Then maybe this Jenks hopped off, in the morning, met the ‘plane Mr. Tredway was flying, forced it into trouble, rode it down——”

“But we saw the big cabin ship!” objected Bob to Curt’s theory. “There was no other ship around.”

“You can’t be sure!” argued Al. “That brown crate might have been up above, against the dark clouds in the sky! You couldn’t tell if we heard one or two engines. He could have surprised Mr. Tredway, could have driven him into a dive—something may have gone wrong——”

“But Barney examined the craft when it was hauled in,” urged Bob. “Nothing was wrong with it at all!”

“Yes, we did! No name we know. No one mixed up in the case. It was probably hired by wire, or telephone, from somebody we don’t know.”

“It isn’t important, anyhow,” Curt declared. “Not right now. What do you think of my idea, Griff?”

“Then—let’s do it!” Al jumped away from the group and was already at the door. Bob hesitated a moment, then, seeing how eager Curt was to echo Al’s enthusiasm, he agreed.

After the two started for The Windsock, Bob sat with Griff, giving him the facts they knew, the theories they had formed for awhile.

“It’s tangled up, and no mistake,” Griff, recovered somewhat, but no longer fidgety, feeling that aid was being given him in his trouble, rose. “Look here, Bob—I was so excited, I didn’t eat any dinner. What say you stay here in case a call comes in, while I run out and get some coffee and sinkers?”

“Right! I shan’t need the slip that has the combination on it, any more.” He put a paper in a small drawer, closed down the roll top, adjusted his cap at a more confident, rakish angle, and sauntered out, while Bob made himself comfortable at the desk in the swivel chair.

In the deserted office building there was almost no sound—a rat crept toward a wastebasket, ran back as Bob moved in his chair; but otherwise the place was very still.

“There’s an airplane engine!” Bob mused, as, in the silence, he caught the faint, steady drone coming from the sky.

Bob went to the window. The sound seemed to come from the other side of the building. He ran across the hall into the directors’ room and got to the window, which had a fire escape stairway outside it.

Just as he peered through the bars of the fire escape, he saw a craft swoop down, quite low. It did not land! Instead, it seemed to zoom along and to rise swiftly.

“Overshot the field,” Bob mused. “Why doesn’t he drop a Verey light to signal the watchman to turn on the landing floods? Or—maybe the watchman isn’t out there. I’d better see.”

He ran down the stairs and out into the yard, across it and onto the small landing field. The craft had passed, but he could still hear the engine. It seemed from its change of location, that the craft was coming around in a spiral.

Bob ran toward the switch controlling the flood lights. One of the large, hooded lamps was near it. As the sound of the engine came closer he switched on the floods.

To his surprise the sudden light seemed to startle the pilot—at least the craft seemed to waver, to skid, to drop, and then, to catch its flying speed and control. But it did not spiral as he expected a pilot who had waited for light would do.

Swiftly, eagerly curious, Bob caught hold of the handle on the adjusting mechanism of the flood light. It could be lifted, or set lower, to govern the range and height of its beam.

Bob proposed to use it as a searchlight, to illuminate the craft if he could swing the heavy lamp upward in time.

For answer Bob pointed excitedly toward a brown, sharply outlined craft, climbing, growing dim in the fainter beam as it receded.

“It’s—it’s—” he gasped, “—it’s the mystery crate—the brown airplane!”

CHAPTER XXIII
BOB PURSUES!

Realizing that the watchman did not know what he meant by “the mystery crate,” Bob hurriedly told of the earlier experiences: all the while he talked his mind was busy, underneath, wondering why the pilot of the brown ship had flown over the plant, why he had appeared to lose control when the light flared up, why he had climbed to get away.

“Look here, though!” he cried, beckoning as he ran. “In the hangar is a crate just like Griff’s model—belonged to Mr. Tredway. He—he won’t need it no more. Whyn’t you?——”

“Sure! Once you get off the ground, the air’s all the same, day or night, ain’t it?”

Not exactly, Bob demurred, There were many considerations to be thought out, but his father had said “locate the brown ship.”

“Can we get the crate out? Can we get it started? Is there any fuel aboard?”

Already the watchman had hold of the tail assembly of a trim, slender, dark fuselage.

“Grab on!” answered the watchman, jockeying the fuselage so that a wingtip missed the span of the cabin ‘plane’s spreading airfoils. “Grab on! I know you lads is detectiffs, and here’s your chance for a medal or somethin’.”

Bob “grabbed on!” with spirit. He had caught the enthusiasm of the older person. It took them only a short time to jockey the craft into the open, to get its gauges checked, to see that it had oil and at least a tank of gas three-quarters full.

“Contact!” he yelled, stepping swiftly beyond the range of those deadly sharp blade tips.

There came the snap and bark of the motor. Cold! But Bob, feeling that for all the precious seconds it must waste, he ought to be safe before he might be sorry, allowed it to warm up, checked his instruments as he had observed Lang and Griff do, and then, as the watchman, obeying his signal, kicked away the chocks so the wheels could move forward, the amateur pilot, steady and cool all at once, glanced at the windsock, saw that he could take off straight down the short field, pulled open the throttle, tipped the “flippers” so the tail ceased to drag, as the propeller blast caught the elevators, and began to race down the field.

As he went he tipped the elevators sharply, felt the ship sway a trifle, realized he was off the ground and moving steadily, climbing to the roar of the engine!

He smiled a little. He had not forgotten to hold the ship level for the brief seconds that it needed to assume flying speed after the first hop from earth. He had not climbed her at too steep an angle, there was no indication, at least to his inexperienced hand, of any logginess of the controls presaging a stall. He was away!

“Now,” he thought, with a sharp glance around the sky spaces, “I am in for it. If nothing goes wrong with the machinery or the prop I guess I can keep this crate level and get somewhere.”

“He was mightily interested in the aircraft plant,” Bob reflected, letting the ship “fly herself,” as most well balanced aircraft will do in steady air, as long as flying speed is held. “Now all that we have found out, so far, has centered about the aircraft plant and—and The Windsock! Could he be around there? Or——”

“—Or, maybe he’s brought the brown ship back for some new stunt! It might be hidden in that field again!”

He pushed the stick a trifle to the side, thus operating the ailerons, while he used his rudder experimentally, meaning to swing in a circle.

Whether a good Providence watches over amateurs, in sports or in professions, or whether Bob had actually learned from his lessons, the fact is that he did not overbank or use too much rudder, and neither felt the wind of a skid on one cheek nor the breeze of a slip on the other. Around went the ship, in a wide swing.

Bob kept his eyes on the sky, with momentary glances at the instruments, not all of which were understandable to him yet; however, he knew the altimeter, the tachometer which records engine speed, the gas and oil pressure gauges and such important ones.

They seemed all to record satisfactorily. His altitude was six hundred feet; a little low for safety, so he climbed to twice that. The revolutions were even and plenty for his need, as he watched the fluctuations of the tachometer when he eased the throttle forward in his climb, or backed it gently in the level-off.

He nearly lost control in his excitement, but with the true air-sense he caught the tendency of the sideslip by opposite rudder and aileron and then banked and circled till his nose pointed straight for the dying flare.

“I’ll get there soon! And see!” Bob told himself. He held the ship level, glancing at the “bubble” in the spirit level, as he gave the gun, opening the throttle steadily.

To the roar of the engine, the sing of cool wind in taut wires, the sting of pulsing blood pounding a thrill-song in his temples, Bob took up his quest, and soon saw, ahead, the dim outline of a circling ship. It was dark. Was it brown?

He dared not get too close. Rather, he preferred to climb, so as to be safely out of the other fellow’s way if he maneuvered.

From above Bob planned to light a white flare, by whose light he could identify the ship.

Bob needed no flare to tell him that he had discovered the brown craft—its action was indication enough! The pilot dived, and then went into a barrel-roll, dangerous at a low altitude, Bob thought.

The “stunt” enabled the ship to get to one side and out of his line of flight if he dived for it.

But Bob had no such intention, he merely followed as the small, brown craft, speedy and capable, went fleetly through the night.

Bob, easing his throttle a little more open, as he got the line of flight, held his elevation and his level position; he did not try to overtake the other, he wanted to see where he went—nothing more!

So the flight held, one about five hundred feet up, the other easily as high again. The speed was almost identical, the ships were well matched.

He began to climb. Bob, fearing to be over-reached, climbed also. Higher, higher they both went, Bob still atop the other, for he had as much power, as well angled wings, as clever a ship as his adversary.

But the battle of elevation was short. At fifteen hundred feet the brown ‘plane went into a wingover, and to Bob’s dismay it was, by that maneuver, in a reverse direction to the flight of his own, and he dared do no maneuvering, no stunting, at night and alone!

Before he could swing in the easy circle which his inexperience compelled him to use, the other pilot was almost out of sight. He climbed, and thus Bob gained, but he saw that his pursuit was futile.

In its misty vastness, surrounding a ship like a fog, an inexpert pilot could not know, without continually watching his spirit level and other instruments, if he flew level or on his back, if he was going sidewise or straight toward earth. To watch the instruments “to fly by the dashboard” was useless; he could not see to follow if he risked the feat.

Disgusted, disappointed, he cut the gun and slowed his ship, and flew around toward The Windsock. Somebody on the ground was burning several land flares, he saw.

It told him one thing! The other fellow had been expected! His signal had been seen.

For an instant Bob was tempted to try a landing, to see if they would be startled, those people down there in the glare. Did they perhaps think he flew the craft they expected? It would be worth something to discover that. Or—would it? The danger, the risk, was considerable. It was strange territory to him. The people, seeing his craft markings, its different color, might extinguish the flares, leaving him, low, to “set down hot” or to climb, too late, and land in trees!

CHAPTER XXIV
SUSPENSE!

When Al and Curt, riding easily, reached the region of the Rocky Lake Park, they hid their wheels in the well remembered field, preferring to advance on foot, to spy out conditions before arriving at the roadhouse to which they were going.

“There’s something going on, over there,” said Curt, as they walked, facing traffic, along the familiar highway.

“But they won’t chase people away! It would be bad for the business!” chuckled Curt. “Every young man can have—must have—at least two in his family, and they might be dancing papa and mama.”

The new dance floor, built in an old-looking, metal-covered addition at the side of the main hotel, was crowded. A “jazzy” orchestra, with many toots of its saxophones, howls from clarinets, trills and staccato yaps from its trumpet, put rhythm into the march of many feet.

“Makes me wish I had a girl and had her here and knew how to dance,” laughed Curt.

“What I wish more is—” Al did not get time to express his desire to have Bob along, to advise him in his rather impulsive acts. A man in a dress suit, as the drums rolled in warning to attract attention, advanced to the edge of the band platform and addressed the dancers applauding their last “number.”

“Lay—deeze—an’—gemp—mum!” Al nudged Curt and whispered that the man was Jenks. “For this opening night the manage—munt has went to the special expense—youse mus’ excuse my poor way of speakin’. ‘I’m only a simple flyer, an’ my eddication don’t go no higher’——”

Al exclaimed, and Curt scowled at the aspersion thus put on the intelligence of the most manly, most steady, best educated general class of men in industry—pilots!—but they listened, nevertheless.

“The manage—munt has put on a extra fine show for tonight. In fact, folks,” his manner became more natural, “we’ve engaged a stunt flyer to come over here tonight, to fly around up in the dark blue, and to do stunts, with rockets and colored lights so you can see what he does. I understand the whole crate is to be lit up some way. So, if you’ll all step outside, while we put tables in here for refreshments, you will have the free entertainment as soon as we can get his signal and let him know to go ahead.”

While the laughing couples gathered, a small, red flare was visible. The men who seemed to be awaiting this signal, lighted flares. But to their amazement the ship did no stunts! It went away!

“Funny!” muttered the excited, disgruntled manager, Jenks, close by Al and Curt.

As the flares brightened it seemed as though there were two airplanes dimly reflecting the light.

“But they aren’t doing any stunts!” complained a girl to her partner. “Wait!” he counseled. Waiting, however, did no good.

The dancers, murmuring, and the manager, trying to apologize, saying it must not be the right crate, went back to dance, shoving the refreshment tables roughly aside.

Al and Curt, waiting, watching, wondering, saw the men stick the stubs of their flares into the ground and walk off.

“Look! He’s coming back!” Al pointed to a speck. They listened and heard the drone of an engine.

“He’s back again!” shouted Al, and the people came out again, standing with backs to the glaring light, shaded eyes turned upward.

“Look!” Curt caught Al’s arm. “He’s in trouble—isn’t he?—yes, he is! Listen! His engine has stopped—dead!”

“He can’t land here,” said Curt. “He’s too low to spiral and shoot this little clearing—anyhow, it isn’t a place to land—not for night landing!”

“I wonder if the same things are happening that happened—when Mr. Tredway was—lost!” Al murmured. “That time, we heard the engine, and then the ship dived.”

An airplane had been cruising over the flares. Its motor had stopped. That was sure.

For he was the pilot whose engine stop had left him with a “dead stick.” He must glide. He had enough gliding angle, he supposed, to take him back to that providential field—if he could throw over a flare and make some sort of a set-down!——

For, in spite of its danger, knowing well what might happen, Bob had shut off his own engine—deliberately!

Appearances are deceiving. To Al and Curt, on the ground, with darkness, distance and trees to screen the truth from them, it seemed as though the glare they saw beyond the grove must spell a blazing airplane.

As he headed over The Windsock roadhouse, and decided to give up, to return to the aircraft field, he had all of his mind and attention on his craft. Because of that he was able to notice a mystifying, if tiny bluish light, intermittent and flickering, close to the pipe that conveyed fuel from the tank to the mixing carburetor.

Somehow, either through one of those malicious acts which had already been done to other ships, or from a rubbing wire, some electrical conducting wire had worn off its insulation and was bare, and each time it rubbed or touched metal it made a spark.

If there is one thing more dangerous than another in the air it is the menace of an open spark close to gasoline feed lines and carburetor mixing chambers.

Knowing it well, unable to determine the cause, but sure that the spark was electrical and dangerous, Bob took the only safe course. As Curt and Al had observed, his engine stopped. He cut off the ignition.

“Now,” thought Bob, “I daren’t use my motor. That means I must glide. At this height, if I remember what Lang said, the angle that will give me safe flying speed will about take me to that little field we first saw the brown ‘plane hidden in. Can I make it?”

He depressed the nose, watching, by his sense of touch, how the stick and rudder bar acted. As he moved through the air he elevated the nose a trifle, to get as flat a gliding angle as he dared; but his whole mind was concentrated on that feeling, that sense of heaviness in the reacting of the controls. When they began to respond sluggishly he knew enough to sense that he was losing flying speed, approaching the danger point called stalling, in which the ship gets out of control, drops or slips or does some other uncontrollable maneuver.

Always, in time, he lowered the nose, picked up the needful speed, and thus, by coming as close to the “graveyard” glide, or flat angle, as he dared, and yet conserving enough reserve speed to keep the lift of the wings more sustaining than the downward pull of gravity, he held his craft in the air.

Always the nose, pointed into the wind, went lower. Always, as he tried to penetrate the darkness of the night and of the brown earth below, his eyes, over the cockpit cowling, searched for the flattish, light spot he wanted. Along its inner side was the strip of turf he needed.

“Can I glide that far? Will I overshoot or undershoot? Will I misjudge the height as I come down, if I do make it? Will I set the ship down too suddenly, so it will bounce off and then—with too little margin of height to get speed again—crack up? Will I stall too high and smash down? Will I be going too fast, and run too far? Can I glide in to the turf or will I set down in stubble and nose over?”

Resolutely, by all the will power he had, Bob crushed out those nerve-deadening, muscle-binding terrors.

There was the field. Where, now, did they keep the light producing flares? Oh, yes! There, in that little boxlike compartment.

He flung a detonating flare that would light in the air or on striking earth. Its light was what horrified Curt and Al.

The white gleam showed, far ahead, faintly lit, the field. His course would take him toward it, but he altered the direction of his flight slightly to get over the turf, then corrected the bank, leveled his wings, depressed the nose still more, picked up speed and, with all his force, sent a landing flare into the air, as far ahead and to the side as he could fling it.

Then he “shot” the field, got his nose directly onto a line with the large trees at the end of the field, pulled up the nose more, to kill all the forward momentum he dared, and then——

Bob gasped. He was too far to one side. He would land in the stubble. Also, he was a little too high.

Then, from some hidden source of remembered instructions he got the instinctive knowledge of what to do.

He dropped the left wingtip by pushing the stick sidewise, and felt the ship tilt. It went into a sideslip. That both lost speed forward and got him further over to the left.

Opposite rudder, hard! Up left wingtip, down right! Nose down a little! Speed enough to go on!

With his heart in his mouth, looking swiftly down, Bob saw the earth seem to come up at him. Up elevators! Stall. He’d have to take it! He was close to earth, over turf. He must not keep that nose down and glide into the trees or taxi beyond the end of the turf.

CHAPTER XXV
CROSSED WIRES

By the time Curt and Al got their bicycles and pedaled to the vicinity of Rocky Lake, Bob’s flare was out and they had no means of ending their suspense until they had looked around in the picnic grove and assured themselves that there was no burning airplane in sight.

They pedaled faster. Presently the pair reached the field; soon Bob, using a small pocket flashlamp, was telling his brother and his best friend how the electric spark had worried him.

“I knew the brown airplane was gone,” he continued his explanation, “the only thing left for me to do was to head back to the plant. But I saw that quick little flicker close to the gas line and cut off the ignition switch.”

“Tracing the wiring,” Bob told his brother. “And here is a wire! It ought not to be run so close to the gas line! And here is another, away back under the dash instrument board. They cross!”

“Certainly not!” agreed Bob. “We’ve learned enough about airplane construction at the Tredway plant to know they don’t do such careless things as that!”

“Then somebody deliberately did it,” concluded Al. “It’s part of the scheme to damage the crates.”

“It’s worse than that!” Bob climbed to the ground and faced his companions. His face, hard to see in the dark, because he was saving his electric battery, was very serious. “It’s worse than just tampering! Fellows—this is Mr. Tredway’s own airplane!——”

“I see,” commented Curt soberly. “Some one wanted harm to come to the owner of the plant.”

“And the ‘some one’ made sure it would. In daylight,” Bob stated, “that spark wouldn’t be noticed. It was only by being out in the dark of night, that I could see it.”

“But crossed wires ought not to rub enough to wear out the insulation in a short time,” objected Al.

They were silent for a long moment. The full wickedness of that deliberate act made each of the youths feel rather cold. They were dealing with something more sinister than an attempt to make away with small airplane supplies, to damage airplanes for the purpose of injuring the reputation of the manufacturers, as they had decided the conditions seemed to indicate.

“Well,” Curt became practical, “you can’t fly that ship home, not in that condition.”

“If we had some adhesive tape,” Bob said, “I could tape the wires and get back to the aircraft field.”

“Maybe I could do it,” Curt responded. “My hands are thinner and my fingers are longer than yours.”

As soon as Al brought the roll of pitched fabric, Curt, with the flashlamp set for steady burning, located the damaged insulation and began to work with strips of the tape, having some difficulty in winding it without pulling the wires too much.

“This is going to be a slow job,” he called out. “Bob, somebody ought to go and call up Griff, to see if he has any news.”

“Why don’t you both go!” Curt urged. “One could stay at The Windsock and watch and the other could come back with news—or, Bob, you could ride back on my wheel, to The Windsock with Al, and then come on back here and we two could fly back to the hangars together.”

“Would you trust yourself with me, in the dark, flying this ship?” asked Bob. “Something else may be wrong with it.”

“That’s so. I’ll look it over. I know how they inspect them,” Curt suggested.

“There’s that ‘plane again!” Al pointed to a tiny red flare high up over the roadhouse ground. “He has come back.”

“I suppose I frightened him away,” Bob said. “He probably thinks whoever chased him has given up, and he has come back.”

“One thing bothers me,” Al observed, forgetting his weary legs in the fresh excitement. “Why would a crate that has a pilot who flies away from pursuit come back to do stunts?”

“I can’t answer that,” Bob replied. “Let’s get there. See! He is looping, and he has lighted some sort of rocket or bomb that makes a trail of fire to show his stunt off in the dark.”

Bob agreed with his brother’s exclamation as the airplane, high above them, with fireworks leaving a comet’s tail behind it, made a series of loops, dived, zoomed, made a sort of “S” of fire by side-slipping first one way and then the other.

When they got back to the roadhouse the display was over. Ground flares were going and it was clear that the pilot meant to land.

“We’re going to see who it is, after all,” declared Bob, thrilled by the possible revelation that was to come.

Curt saw the gyrating ship and its glowing trail of sparks. He watched for a moment and then went doggedly back to his work. If Bob needed this sport craft, Curt proposed to have it ready if careful, methodical work could get it so.

Surprised, he heard himself addressed by a youth who came over from the farmhouse whose builder owned the field.

“Some display for the opening of the roadhouse dance floor,” Curt replied, tightening down the tape and clipping off the end with his pocket knife.

“I don’t—I’m not the pilot,” Curt stated. He explained. Then, his task finished, he clambered down to see the glow of the distant, concealed ground flares, and to guess that the sky rider was going to land.

“This is gettin’ to be a regular aviators’ place,” said the youth to Curt. “Guess pa ought to put up signs, ‘Places to land for rent.’”

Thus having the spot indicated, even in the dim light Curt was able to see that deep ruts had been made, not only in the soft, ploughed edge of the field, but also on the turf.

“Hm-m-m!” he had no explanation to comment. It was unimportant. Something of greater concern was on his mind.

“See here, buddy,” Curt said, “will you help me ‘warm up’ this ship?” He was searching for two stones or blocks big enough to hold the airplane still while the propeller revolved. “The pilot might want to take off now that I’ve fixed the damage.” The boy agreed. Curt, locating several rocks near where the brown ‘plane had once been hidden, set them under the wheels, and then, realizing that the ship must take off facing into the wind, he got the youth to help him drag the tail around, to pull the whole ship as far up at the end of the turf as possible.

“‘Crate,’” Curt corrected, smiling in the darkness. “That’s a slang way of speaking of an airplane, and it means either a term of fondness, or of disgust, according to how the user feels about his ‘ship.’”

“You can, if you are willing to study enough,” Curt said. “It means hard work. There’s a lot to learn. But a fellow who has ambition can get to be anything he likes.”

“You can pick up some education while you’re studying in ‘ground school,’” Curt explained. “After you learn the parts of the airplane, the way each one works, what it is for, and so on, and how they are put together, you have to study about airplane engines—the principle of the internal combustion engine and what all the parts are for and how they work. There has to be study of—let’s see—oh, yes!—aerodynamics—how a ship flies, and why, and what different air currents do, and how to know their effects. There’s navigation, too—the beginnings of it, anyway.”

“If there weren’t so many people who thought that,” Curt said soberly, “we wouldn’t have so many accidents. Flying is a science; and there’s more to it than getting into the air and going somewhere. It takes ground school study to learn the foundation part, and instruction flights to learn how things are handled, and solo flights and stunting to show you how to handle a crate in an emergency—and navigation in its practical applications, for long flights. But if you are in earnest, you can get all that, and pick up practical arithmetic and grammar and so on, in night school at the same time.”

“No—unless—you might come over to the Tredway aircraft plant and I’d introduce you to Barney—Mr. Horton, the manager. He might give you a chance to work as a ‘grease monkey’ in the field, for he is awfully nice. He helped all of us.”

The youth agreed eagerly, and then, with the chocks set and the ignition switch off, Curt told him how to work the propeller around, and got him back to safety as the ignition switch followed the gas “on.”

The engine took up its roar, and Curt knew enough to shut down the throttle to idling speed, allowing the slow revolutions to warm up the power plant. He knew little about oil pressure and instrument readings, but he knew that an engine, to function safely and steadily, in flight, must be warm.

While he busied himself getting everything as nearly ready as his ability allowed, Bob and Al reached the roadhouse.

“Yes,” said Bob. “Now, Al, the pilot must have gone inside the roadhouse. I don’t see him around the dance place. You could go in to ask for his autograph. I see you still carry that little book. It ought to be easy to get a look at him, have him pointed out to you. That’s really all we need.”

Al agreed. He had no difficulty in getting a busy waiter to jerk a thumb toward one of the private compartments.

CHAPTER XXVI
THE SKY SQUAD GOES INTO ACTION

Three men faced one another in the small compartment, made to look like a passenger ‘plane cabin.

As Al, at the curtained entrance, recognized the one facing him, all three turned to look.

The man to his right was the mysterious stranger whom Al had seen in the supply room!

Before Al could form his mental picture of a face that seemed familiar, a bus-boy, with a heavy tray of soiled dishes, bumped against him.

“Get out o’ the way,” the youth grunted, to Al, and gave him an angry push with his free hand. Al, his balance disturbed, stumbled forward—into the arms of Mr. Parsons at the door.

Struggling, squirming to get out of the powerful grip on his arm and shoulder, Al found himself held as if in a vise.

Suddenly his whole body went limp. His head dropped, his eyes closed. He sagged down, and surprised and disconcerted, imagining that the youth he held might have fainted in his fright, the man released him, lowered him to the floor while he looked up, intending to call for aid.

Behind him another face looked out, the bearded face of the man Al had seen previously in the supply room.

“I am!” cried Al, shrilly, as he tensed his muscles, swung free of Mr. Parsons as the latter bent over him. Like the leashed spring of a panther Al’s squirming, swift move took him out of danger.

To cries, to shouts of surprise and of inquiry, Al eluded the grasping hands of a waiter, dodged a diner’s gripping fingers, evaded the move of a man to block him at the door, and was free!

Quick thinking and a ruse had prevailed where strength was not enough to accomplish his wish.

Speeding along, outside, after vaulting the veranda railing, Al quickly located Bob. With a wave of his hand Al signaled. His progress was swift as he scampered across the parking space, between standing automobiles, toward an old barnlike structure backed into the grove. Bob, seeing the wave and Al’s progress, dodged, on his own part, among the cars until he rejoined Al in the open door of the old, dilapidated barn.

“There was somebody else with them. And—I didn’t recognize him, because I was so surprised and excited—but his face ‘rang a bell’ and I’ll think who he was when I get quieted down.”

“Listen!” Al drew Bob further into the dark interior. “Bob—when I blundered in on them, those men had—what do you suppose?—the company books!” Al clutched Bob’s arm tighter. “You remember, we hid when Mr. Parsons was in the offices—he took those books!”

“Yes,” Bob’s whisper agreed. “Now he’s been showing them to that man we saw, and to somebody else.”

Bob shook Al’s arm reassuringly. “No,” he admitted, “I thought Griff’s story was part of—what did they say in the war?—oh, yes! It was ‘camouflage.’ Fancy paint to conceal something.”

“They may be coming to look for you. Mr. Parsons must have recognized you, Al. I wonder if there’s a haymow over this old floor?”

They hurried away from one another. Presently Bob called out softly and, following the wall, with one hand touching to hold his place, the other extended ahead to avoid bumping into any obstruction, the youngest of the Sky Squad found his way to Bob.

There was a ladder against the wall. Bob whispered instructions and started up the dark, uncertain ladder. Bob had hardly reached the top and called down a low reassurance when Al almost scrambled in his eagerness to get up quickly.

At the top of the ladder, Al fell softly onto the upper floor boards, and he, with his brother, bent attentive, strained ears to catch the low murmur from below.

“He’s from the plant,” a voice called, and Bob recognized the quick, sharp tones of Mr. Parsons. “He was a boy from the plant.”

“You got those books wrapped in record time!” someone else chuckled. Then, as the youths drew their heads back, turtle fashion, to avoid the glare, a match was struck.

“Better go up and have a look,” said a third, deeper voice. “We can’t afford to have those kids snooping. I think Barney brought them into the thing. They’re only kids—but they have eyes!”

Bob, with a twist of his neck, looked around in the dim upper room. Its end window, dirty and cobwebby, allowed the moonlight to stream in. The shaft of dull light streamed across, slantwise. Bob, following its path with his eyes, touched Al’s arm. Gently he directed his brother’s gaze toward a corner.

By common consent the two began a slow, cautious movement toward the sacks; but Bob, quick in an emergency, drew the whole pile, very cautiously, partly lifting the lower ones, to a darker place.

Al, close beside him, divined his idea. They could hide under the large cluster of heavy burlap bags.

By the time that a match was struck in the upper floor they were lying, crouched, under a number of the burlap bags.

“Wait, though.” Bob’s breath almost stopped. Had the other man who came up discovered the sacking?

“Wait, though,” the man repeated. “We meant to compare the books tonight; that’s why I took all the trouble with those stunts, to have a logical excuse for landing here. We can’t, now! Those kids may have telephoned somebody—whoever they’re working for. Suppose we hide the books, and get together tomorrow night. I’ll take the crate back and come over by train.”

In their stuffy concealment the brothers heard steps, low muttered suggestions. Evidently a place to sequester the company records was selected. The youths quivered and Al nearly screamed aloud as a sack was dragged from the top of the pile. But the sack did not pull off the ones they clung to over their perspiring heads.

“That’s the stuff! On that shelf, and cover ’em up. Nobody would think of that place.”

The voices receded. The heavy tread ceased. Scuffling sounds told the brothers that the men had descended the ladder.

“They said ‘on the shelf.’ Feel around, as soon as they are out—wait! Al, I’ll slip over and spy out through the window——”

Al sat on the floor, among the sacks, mopping his brow which was wet with hot perspiration that had, a moment before, been ice cold. Bob waved across the bar of moonlight. The trio of seeming conspirators was safely away, he indicated.

With his head, though jarred only slightly, Bob found the shelf. A quick exploration defined the books, in a compact roll of tape-tied cloth, hidden under the sack. It was a second’s work to remove them and to rejoin Al.

Alertly, and with caution, Bob protruded his head over the edge of the opening by the ladder. He was fortunate! In the doorway stood the unrecognized member of the party, smoking. Evidently he had returned.

Bob watched, holding Al in check by his grip on the younger one’s arm. The man did not propose to leave, it appeared.

The sound of an airplane motor starting conveyed the truth. He was waiting until his ship was ready before going into the open.

But Al, try as he would, could not suppress the horrible inclination to sneeze, induced by the dust in his nostrils from the dirty burlap.

“Huh—sh—huh—sh!” he tried to hold back, but Nature got the better of his will.

Like two swift gazelles the youths dashed across to the window, wide and old. It was part of the door through which hay was drawn up, they discovered. They tugged at it. On rollers, but stiff from disuse, it stuck. Panting they struggled. Closer came the ascending steps, a call to know who was “up there!”

Bob hung by his hands, gave a swift glance down, let go! No sooner did he land, with loosened muscles to avoid the shock as much as he could, than the package of heavy books landed beside him.

Al, almost caught, doubled with a swift, bending squirm, as the angry man reached to grapple with him in the moonlit doorway. By his quickness Al was able to get away for an instant.

He tried the same ruse he had used so well before, but in another form. Every ounce of weight he could put into it he gave to a run away from the ladder. Then, doubling on himself, but tiptoeing and bending as low as he could, avoiding the moon ray, Al crept softly along. The man, following the direction of the footfalls, and thus trying to locate his quarry in the dark, did not see the silent, gloom-hidden form slip along the wall. Al was down the ladder before his ruse was detected.

Bob, racing toward the bicycles, realized that the other two men, catching the warning shout, were bearing down on him. Like a rabbit he reversed his route, slipping in among the trees behind the barn. But Mr. Parsons and the other mysterious stranger were determined men. Bob could not run and be silent. He dared not creep. They were too close behind him.

Al, seeing that this pursuit was close, tried to divert attention by shouting as he ran, openly, across toward the bicycles.

But this did not draw the others away; they felt that Bob had a parcel for which they meant to catch him. On and on, through the grove, dodging, squirming past trees, through briers, Bob went.

Curt, at the field, with the engine idling on the airplane, did not hear the pursuit until Bob, almost worn out, nearly done, came racing along. Then, seeing him, Curt ran to meet him. From the grove behind came the crash and shout of pursuers.

Curt caught the package as Bob hurled it. Then, with an instinct that amounted to genius, Bob noted a flattish stone, and as he ran he bent, pausing an instant, and came up tugging along the small, flattish boulder that, in the dark could be mistaken for the package of books. Unconcernedly, as though watching in the role of a spectator, standing on the parcel of books, Curt remained quiet, and the men raced past him.

From the road, where he flung his bicycle, knowing well where Bob would head for, Al arrived. He raced toward the airplane just as Bob ran in the same direction with his boulder.

Al, not unnerved by his excitement, realized that if the propeller was turning, some chocks or other means of holding back the ship were in place. He bent under the wheels as Bob arrived.

“Get in!” he cried. Bob, pretending to drop the books in, let the boulder fall beside the turf. While he was climbing in, the men paused for an instant by Curt who said, sharply, “There he goes!”

Al tumbled into the rear cockpit, determined not to be caught after the enmity he had awakened.

“Take me!” he cried, but the roar of the engine drowned his voice as Bob, risking everything, in the dark, opened the throttle.

Up went the elevators enough to lift the tail as the propeller stream swept against them.

Along the turf the ship began to move. The men, aware of the sinister menace of the whirling blades, fell aside. Bob, sensing the near approach of the end of his runway, lifted the elevators again, felt the ship going light, gave her the gun, holding her just long enough on the level after the take-off to get his speed—then up he roared.

And a boulder beside the turf remained, while Curt, with the books under his arm, among the trees, went to Al’s bicycle—and delivered the books to his uncle’s study.

But he didn’t stay at home. Mr. Wright was not there. Bob and Al would fly to the plant. Thence, on tired feet, Curt pedaled.

CHAPTER XXVII
DRIVEN DOWN

Almost as soon as he lifted the airplane above the grove beyond that cornfield, Bob recovered his wind and his confidence.

Al, of a more nervous type, was still trembling in his after-cockpit seat, but his excitement was changing from that of the recent adventures to the thrill of sky-riding at night with his brother. There was not only the elation of the climb to keep his nerves quivering; also there was the uncertainty of what might happen because of Bob’s lack of skill and experience.

Climbing steadily until he was over five hundred feet above the earth, Bob felt none of his brother’s uneasiness or excitement. He was confident that he could control the airplane as far as straight flying was concerned; his only difficulty would be the landing, not the easiest thing for a skilful pilot unless a signal could be given that would make the plant watchman illuminate the small field.

Bob, making a long swing, banked gently, to head back for the plant, calmly considered the elements of the situation and tried to plan, as well as he could, how to meet whatever came up.

Al, giving more attention to sky and earth, as they straightened their course, correctly pointed for the field at the plant, saw a tiny set of glinting lights far away in the sky.

Impulsively he caught the stick of the dual control to waggle it. That was the only way to attract Bob’s attention; but Al, in his quick way, shook the stick and then held it pretty far to one side, and Bob, not expecting the move and unaware at first that Al did it, felt his heart sink for an instant, fearing that something had gone wrong with the controls.

Al, horrified at the effect of his move, sat, tensely still, waiting for a crash. Bob, alert, decided in a flash that he would do all he could to avert the smash before he gave up hope. He made the necessary moves to correct the slip.

To his delight the craft obeyed promptly, coming back into its proper position quickly. Turning to reassure Al, Bob saw his brother violently gesturing toward the sky to one side. As he looked Bob saw tiny lights and knew them for the flying lights of a craft.

The explanation came at once. Al had attracted his attention to the airplane knowing it must be the brown ‘plane. Probably the two men who had chased Bob had contrived to tell the pilot, before he took off, that—as they supposed—the company books were in Bob’s possession. With a wave of his hand toward Al, reassuring him, Bob set his course for the flying place belonging to the Tredway plant. He was being pursued by the ship he had, recently, followed; it suited him. He would lead the ship back there, contrive some way to attract attention, get Al to drop flares, and then, landing, telephone all the airports nearby to identify and stop the pilot who must eventually alight for fuel.

Bob realized it, at the same time that he recalled how swiftly the other pilot had climbed to escape identification earlier at the plant.

Instead, the brown ship had some sinister intent toward himself, Bob guessed, for it was climbing rapidly, and Bob, unaware of the safe climbing angle or stalling angle of his own craft, dared not risk so steep a tilt.

He proposed to gain all he could in speed, and that meant distance ahead of the other, while that other airplane climbed. He knew he could fly faster, on the level, than a climbing ship could, and he saw the other lights slowly becoming somewhat fainter, smaller.

In a few seconds the other ship leveled off and began to approach. Bob, craning his neck to get a sight of the other craft beyond his own wing spread, saw that the other man, evidently angling down and pointing directly for a position above him, meant to overtake him and was quite capable of doing it. He had superior experience and skill.

Bob realized quickly that the better part of valor in an airplane at night, under such conditions, was to give up.

To carry out that pretence he reached into the signal light stores and selected a light. This he tossed back to Al.

Al knew that Bob wanted light. He ignited the flare, which proved to be a green signal blaze, flung it overside and watched its tiny parachute catch the air and suspend it.

The other pilot, arresting his dive, also flew along level, and watched, it appeared.

Bob, lighted by the glowing green flare, pointed to himself and then pointed to earth.

The other ship, coming steadily closer, was quite plain in the illuminated space. Its pilot made a similar gesture, pointing first toward the airplane Bob piloted, then downward.

Bob lowered the nose and began to spiral, as though looking for a spot on which he might safely “set down.”

Swiftly Bob summed up the situation. Beneath him, easily reached, was the wide ribbon of the asphalt highway. By heading almost directly into the wind he could “shoot” the road, and by keeping his engine running at partial speed he could make a “power stall,” letting the craft settle very gradually instead of trying to glide down, guess at the correct height and then stall and drop. To do the latter in the comparative darkness of the highway might result in smashed landing gear or worse if he stalled too high and dropped, or it might happen that he would “put her on hot,” or at too great speed and without stalling, come against the ground. In one case out of ten that might enable him to roll along, but if he struck the slightest uneven bit of road, or a bulge of the tar at the intersections of the asphalt road blocks, up would bound the ship, perhaps to stall herself and crash.

By using power he could keep flying speed while gradually settling until his wheels contacted the road. He could also rise more readily if he discovered that he had gone too far to either side of the narrow road—wide enough in fact but narrow from the standpoint of its use as a landing place.

The man meant “business” and that might spell trouble for an amateur. Better far would it be to set down and see what came of it.

As he saw the roadway ribboned out straight ahead, with no headlights observable in either direction, Bob lifted the nose a trifle, adjusted the throttle until, with the road streaming backward under him, he saw it very gradually growing wider and clearer.

Almost perfectly he landed. Being a straight road he had lots of time to taxi, with his gun cut and his only care being to hold the ship on its wheels and not let a wing-tip scrape the asphalt.

Instead he seemed to be circling at a very low altitude, not a hundred feet up, and with only bare flying speed, diving ten feet to catch up his speed and then climbing back to circle again.

“We can’t leave this crate standing on the highway,” Al called as soon as Bob had the engine running at idling speed. “Suppose a Sunday driver comes along at sixty miles an hour?”

“That’s so. If we go up he’ll ride us down, and we might not make as good a landing—you might not, I mean.”

“The headlights blind me,” he declared, shading his eyes with his cap brim and hand.

“It’s—it’s the ones who are after us,” called Bob. “See! One of them is stopping the car and the other one is jumping out.” He turned to Al.

“They think we have the books. The man in the brown ship drove us down. Mr. Parsons, in his car, with the other man, is coming to get us.”

Al, as soon as he was on the ground, used his heels to good purpose. Bob, pausing only to bundle up some folds of his coat to make it look, from a distance, as though he carried a package under it, slipped to the road and ran the other way.

CHAPTER XXVIII
CURT’S DISCOVERY

“Those books are off my mind,” Curt reflected as he pedaled slowly toward the aircraft plant, “but my legs aren’t. I’d go to bed and rest for a week if it wasn’t for seeing what Griff is up to.”

He had ridden only a block or two away from his uncle’s residence, where he had deposited the books, when a thought occurred to him.

“I know how to get a ‘tow’ to the plant,” Curt whispered to himself, swinging his handlebars to turn into the next cross street. “They usually get shipments of fabric on the eleven o’clock freight, and our truck is there to load it in.” He glanced at his wrist watch.

“Yes,” he told himself, “it ought to be loaded or nearly so—and that means the truck will be starting soon. I’ll ride along till it catches up with me and then let it pull me where I’m going.”

It was a reasonable notion and well-founded. That it was sound was soon proved, for Curt saw the truck turning into the street just ahead, from the direction of the station.

He had expected it to come from the street he had passed, but realized that it must have followed the direction it had been pointed instead of turning around in the station yards; increasing his speed for the moment, Curt caught up with the tail boards of the large truck, took hold with one hand, set his coaster brake, and rode in comfort, resting his weary feet.

He let go and dropped back a few yards, intending to let the truck go; but it bothered him to decide what caused the change of route.

Curt resuming his pedaling, following at a little distance, determined that for all his weariness he ought to find out why a truck, openly laden with cases and parcels, boxes and canvas sacks, should not go directly to its destination to be ready for unloading when the plant opened in the morning.

Curt, keeping at good distance, let the truck get around a bend. He could follow by the sound of the motor. He did not wish to be seen.

When the motor ceased to send its roar across the distance to him Curt laid Al’s bicycle, which he had ridden from the cornfield, beside the rutted country road and walked, screening himself carefully, to the bend.

“No truck should stop in this out-of-the-way place,” he decided. “I’d better be careful. They might have a guard set at the turn.”

There was no guard, however. Evidently the truck driver and his assistant had no suspicion that they were observed.

Openly the truck stood in the road, to one side. Curt, able to distinguish its bulk, was too far away to see through the darkness what was going on.

“Maybe a broken drive chain,” he thought. “Still, I’d better be certain.”

He made a slight detour through the pines along the byroad, being careful to make as little sound as possible, working around toward the position of the truck. Whatever sound he made was soon drowned by the roar of a motor.

“That’s another car coming,” Curt told himself, “and it’s a heavy duty motor, too.”

He made fast progress toward the edge of the trees. There, hidden behind a large trunk of pine, he could see the dim road, the dull outline of the truck, and the moving forms of men lifting things out and piling them by the road.

“They’re unloading the truck!” Curt was amazed. Was this some bold banditry, some open theft?

To his further astonishment and mystification the other truck came along and stopped. There was an exchange of low, but jovial banter between the rough drivers and their helpers, but no allusion was made to their task. Instead, the men on the truck just arrived began also to unload bolts, cases, boxes, sacks, from their vehicle.

Curt could not figure the problem to a satisfactory decision. Were they substituting one load for the other? Why?

At any rate, they would be occupied for several hours, Curt thought. He made his way quietly back into the wood and hurried toward his bicycle.

“I’ll ride to the plant, get the watchman to telephone for the police, and round up those fellows.”

Every ounce of his reserve energy Curt put into his pedals as he bumped along the byroad and then raced down the main highway.

When he came within sight of the aircraft plant he was surprised at the activity displayed. The flood lights were on. Far up overhead he heard the sound of an airplane engine.

“Oh!” Curt was reassured. “It must be Bob and Al coming in. They will be glad to hear I put the books away safely, and then we can all ride back to the truck—no, we can’t!” He recalled that his own wheel was parked at The Windsock—if no one had taken it.

There was no one in the watchman’s place by the main gate, which was open. Curt decided that the man was at the flying field to give assistance to the airplane as it landed.

“Hello!” Al, turning at the door of the administration offices, hailed Curt. “Come on!”

“Must be Mr. Parsons bringing in the ship we deserted on the road. Did you leave that parcel of books at Dad’s? Good! But why did you come back here, Curt?”

“No—we must get to Griff. He must be wild, waiting without any word. I know the trucks won’t wait forever, but you can identify them in the morning. Come on.” Curt followed Bob’s lead, with Al at his heels as they entered the office corridor.

Griff’s voice came to them as they reached the upper landing. He was talking—telephoning!

“Oh—Langley! You got there! Good! What? Your uncle is gone? Gone? Gone! Lang—where? You don’t know? What’ll I do, Lang? You don’t know? Well, I do!” and he slammed the receiver on its hook.

At the safe, kneeling, was Griff. He twirled the dial, clanged back the safe door, reached for the packet of bills again.

Over the offices came the drone of the approaching airplane circling for a landing. Al moved toward Griff.

“Get back!” Griff was furious. Bob, behind him, snatched the packet of bills, flung it into the safe, slammed the door. Griff, with a furious snarl, bent to recover the packet, but the door was shut.

Heedless of the roar of the airplane engine as the ship came low over the office roofs in its descent, Bob, Al and Curt disentangled themselves, got to their feet.

Already Griff was by the safe, the combination figures on the slip in his hand, the dial of the safe door twirling and clicking.

With a quick glance Griff measured them. His face was white, his jaw was set, his whole attitude was that of a terrified, trembling young man who had determined on a course he knew to be wrong but which circumstances would not allow him to avoid.

“You daren’t!” corrected Al. “Your father has stolen the books, but you shan’t——”

The safe door was wrenched open. Bob started forward, Curt at his side, to catch Griff’s hand, to prevent this thing he felt he had to do. His fear of his father’s anger was greater than his dread of the boys, it seemed.

His hand on the packet of bills, Bob tried to stop him. Griff, with a scowl and a wicked word, kicked Bob’s shin, avoided Curt’s grasp, and stood back, his face working.

“Listen!” Al, nearest the door, called the word. They were halted, frozen into statues with tense poses and straining ears.

Instantly, white with terror, Griff flung the bills toward the open safe, kicked the door shut, turned like a hunted animal and ran out through an intervening door into the next office, and, with Bob in hot pursuit, raced across the hall, into the directors’ room, to its window and down the fire escape. And Bob, at the window, felt a hand grip his collar. He was caught!

CHAPTER XXIX
A CONFESSION

Without a struggle Bob gave up. In the dark he did not know who his captor might be; but he reasoned that if it turned out to be Barney resistance would be less sensible than explanation. To struggle for escape if the hand on his collar belonged to Mr. Parsons, would be foolish and might make it harder for his chum and his brother to explain their situation.

In his mind’s eye Bob recalled how the office had looked as he left it. Griff had kicked at the safe door, believing the money had gone in; but it had not! It had dropped on the floor.

Unquestionably Mr. Parsons, or Barney, or whoever held him, had come past that office but had not stopped there, preferring to make a capture of the only person he could put his hands on.

Bob realized that non-resistance was a wise course. As he had surmised, he was led back toward the office. He was glad that he had done nothing, said nothing to explain the situation so far. The man who had hold of him, who urged him along the corridor, was Griff’s father, the man from whom they sought to save Griff.

At the office door Bob, panting and choked a trifle by the tight grip on his coat, took in the situation swiftly.

It looked, from all the appearances, as though Al were dictating from the slip while Curt manipulated the combination, to open the safe; on the other hand, from another point of view, it might appear that the pair had recently had the safe open and were closing it.

What made that more probable to an outsider’s eyes was the package of greenbacks which Al held!

“What does this mean?” Mr. Parsons, half dragging Bob along, made a quick, nervous advance, caught the package from Al with his free hand.

“It means that your—” Al began in his imprudent haste; Bob gave him a sharp, meaning look. Al, catching it, realizing that he had almost mentioned Griff, whom they had previously agreed to aid, was silent.

“It means that we came back here—” Curt began and was interrupted by the angry partner of Mr. Tredway.

“Not content with taking those books,” he said angrily, “you want to take the company money—how did you get into my desk? Pick the lock? That adds another count against you!”

He released Bob’s coat collar and strode to the desk, a flat-topped one in the center of the room. Catching up the telephone receiver, he made a call.

“What’s that?” Mr. Parsons spoke into the transmitter again. “He is out? How soon will he be back? Have him call Mr. Parsons, at the aircraft plant! Yes—perhaps I can give him some tenants for the new cells in the police station.”

Bob, recovering his usual good judgment, began to consider the very difficult situation that faced the Sky Squad.

Al, however, seldom thought before he spoke; more often than his brother, he was sorry for hasty decisions and sharp speeches.

Curt, as thoughtful as Bob, trod on the foot of the younger captive and Al, jumping away, refused to be warned.

“I don’t care!” he cried. “If he thinks two sons of a detective, and their friend will be put in cells for trying to save—oh, all right, Bob!—for trying to put money back into a safe—” he whirled on Mr. Parsons at the sound of the latter’s sarcastic laugh, “—that’s what we were doing! If the Police Chief arrests us—we’ll ask him to arrest you, too!”

“For taking the company books away. For showing them to somebody outside the firm—planning how to get more cheap parts into the plant. Oh, we know all about you!”

“Indeed! Young man,” he swung to Curt. “Please go into the bookkeeper’s room, unlock his book cabinet, and bring all the books you find.”

Curt, surprised, took the small key from their captor, went in and lighted the adjoining office, returning, finally, with an armful of books.

“Bob does,” declared Al, still angry, but becoming a little uneasy. He might have jumped to his decision about the books he had seen. He was always making snap decisions!

“Then why were you in such a sweat to get the others when we tried to—” Al’s voice tailed down to nothing; he began to see how really guilty they could be made to seem. There was entry into the offices at night, an open private desk, a tell-tale safe combination memorandum on the floor, a package of bills beside the safe, for one chain of evidence; there was an intrusion on a private conference, at The Windsock, and the subsequent escape with the books for a second, not to think of Bob’s use of the airplane with no permission from a higher authority than a watchman, and the infraction of State law by landing on a highway and deserting the ship in a traffic lane. Al’s bravado began to evaporate.

Bob, who had remained cool, thinking, was able to see a brighter side to the situation.

“Please, Mr. Parsons,” he began, “don’t call in the police. That would force us to defend ourselves. We could explain what we were doing and why. But we have a—a code of honor, and we would rather have you let things work out without the police—and reporters.”

“Father! You shan’t! You mustn’t! Listen to me. I took that money!——”

The telephone receiver dropped, hanging by its cord to swing unheeded against the man’s leg.

“I’ll confess!” Griff, for all his fear of his father, of consequences, was showing his true manliness. “I ran away, Father, because I thought I had put the money back and locked the safe. I didn’t want to be caught. I thought I could go down the fire escape and get away. But when I saw you catch Bob I came back and listened—I must not let these fine friends stand a night in a cell for something I’ve done.”

Then, haltingly, ashamed and despairing, but honestly, Griff cleared the Sky Squad and told the truth.

“He was trying to get out of his trouble,” Curt said to end the deep silence that followed Griff’s explanation, “and he didn’t want to come to you when you had so many things on your mind.”

“Our cousin has gone to get money for him from Father,” added Bob. “But Father must have started for home before Lang got there, and it was only when the man at The Windsock threatened to come and tell you and make it look worse than it is, that Griff lost his common sense. We came back here to meet each other and saw what he was doing and convinced him it was a mistake.”

The impulsiveness of Al prompted him to “put in his oar,” but his earlier bluster was gone and he kept still.

Bob, quietly picking up the telephone as he heard the impatient voice of someone at the other end of the connection making it squeak, spoke into the transmitter quietly.

“We’ll call you back. Something has come up to make things different.” He hung up the earpiece.

Apparently Mr. Parsons did not notice him at all. Added to the blow given by his son’s confession that he had broken promises and gotten into deep trouble was the knowledge that three loyal companions, with full knowledge of his guilt had not only protected him from himself but had shielded him at the expense of being, themselves, suspected and unfairly accused.

“I beg your pardon,” he said, “I am sorry!” Bob, smiling with some relief, eagerly gripped the extended hand, to be followed by Curt and Al.

“Son,” the voice seemed cool and sharp, but it changed suddenly, “Son, I guess I’d have done better to make a comrade of you than to try to rule you with fear and threats. Come here, Griffith.” The young man advanced, hopeful, but also shame-faced. “Son, we all make mistakes. If we learn not to make them again, that is life’s lesson. I am not a judge. I am—your father!”

“I had to tell you—but I guess if it hadn’t been to save these friends, I might have gone on. I guess I’m a coward.”

“It took more bravery to walk in under the circumstances than to tell your father any other time, I say!” Curt exclaimed.

“I will settle with that fellow at the roadhouse,” Mr. Parsons stated, when forgiveness was assured to Griff and the five occupants of the office were determined to “work together” for a change, “If he has been paid——”

“Why not meet the Police Chief somewhere and have Griff tell him the things that are done against the law at The Windsock,” suggested Al. “Then we could all go there and give evidence of how Jenks tried to collect twice from Griff—and maybe we would find out something about—our own mystery. I think he is in it, some way!”

Mr. Parsons decided that he owed the Chief some explanation of his call and, somewhat over-excited, and not his usual sensible self, he failed to realize just what Al’s suggestion implied—that they make Griff incriminate himself, since he had played at the tables without informing against the hotel. The Police Chief agreed to meet them near the roadhouse, and when Mr. Parsons hung up and turned back to them he was much more calm than they had ever seen him. “If I explain my own purposes,” he said, “it will be easier for us all to understand and get together. I have been trying to protect my absent partner——”

“I know!” cried Al, “I know now! I thought the face of the man in that brown airplane—the one who flew it—was familiar. That’s Mr. Tredway!”

“Yes, alive. This has been a very mixed affair,” the partner declared. “I knew that Arthur Tredway was alive, but I could not speak of it or explain, because we did not know whom we could trust, and so told no one.”

“But why did he do it? Why did he hide and let everybody think he had ‘gone West?’” Bob demanded.

“So someone crossed wires that were scraped nearly bare, in Arthur’s own ship!” Mr. Parsons was dismayed. “That proves his suspicion that somebody meant harm to him. And that is what we hid him away to discover. If the accidents ceased with his disappearance, he was in danger; if not, the damage was aimed at the aircraft company.”

“But you haven’t found out why he was in danger—or from whom?” declared Curt.

CHAPTER XXX
BARNEY GIVES A HINT

While the quintet waited for the taxicab which Mr. Parsons summoned from town, Griff put the money back in the safe, thankful for his escape. Bob, Curt and Al expressed their elation that he was freed from suspicion, and Barney arrived.

“The watchman called me,” the manager explained. “Things got a bit too exciting out here and he thought I ought to know. What is there to tell me?”

“Hm-m-m.” Barney was pleased but thoughtful. “Glad to learn my best friend’s partner is cleared,” he nodded at Mr. Parsons. “Certainly I’m delighted that his son is all straight. And Tredway is alive! Glory be! I’m gladdest about that.”

“The man who gave me everything I have, made me the manager of his plant! I’ll say I’m glad he’s all right. Well, let’s go see that ex-pilot and his wicked two-autograph ally!” he grinned at Al.

“You know what they were doing,” he told Curt. “All you have to do now is check the stuff that is unloaded from our truck in the morning. If that turns out to be poor material, trace the other truck, get your proof—and at least one part of the mystery will be easily solved.”

They went out and packed into the taxicab, giving its driver direction for meeting the Police Chief at the edge of the picnic grove.

When they got there and related their experiences they were daunted to find him decidedly lukewarm about “rounding up” the ex-pilot and his roadhouse manager.

“I don’t think the idea is so good,” the Chief of Police stated. “Griffith Parsons has no receipt. He can’t actually prove that he paid real money, or that he paid at all. Anyway, now that his father knows the whole business, that fellow, Jenks, hasn’t a chance to collect again. He won’t dare try. Just what do you want me to do?”

“There’s this note put on the airplane, and his trying to avoid showing his handwriting by giving me two autographs,” Al suggested.

“In a way I’m sorry to destroy that clue,” said Mr. Parsons, “but when we get to the roadhouse you will see that it has no value.”

“We thought of facing the manager, Jenks, with Griff’s evidence of how he permits gambling to go on—and other things outside the law—and making him tell us what he knows,” Bob urged.

“Oh, I know what you’re thinking,” the officer chuckled as he eyed Bob, Curt and Al. “Graft—hush-money! But that isn’t it at all. As far as Griff’s information goes, we’ll take care of that better by making a raid when the place is crowded and the barn is actually in use for illicit purposes. But, don’t you see what you are doing?”

“I do,” said Barney, and Mr. Parsons agreed again. “If we offer to make him tell with a threat of what we will do if he refuses,—we are ‘compounding a felony’ if we get him to tell anything and don’t go through with the legal steps on the face of our evidence.”

“Oh, well,” Barney saw how disappointed the three chums were, although they admitted the justice of the official’s attitude, “let’s go out and see my old patron and comrade.”

The Chief of Police agreed to look into the charges Griff had made and turned his car to return to his home, while Barney, in one cab with Bob and Al, and Mr. Parsons in the one they had called, with Curt and his own son, went on.

“Why didn’t you tell me you were all right?” he cried, pumping the plant owner’s hand, slapping his back, and, as Al said later, “almost kissing him,” while the mysterious stranger, and the others watched with various feelings.

“I had to make my plans in secret,” Mr. Tredway retorted. “Not even my partner knew until tonight. But—let us get acquainted, all the way ’round.”

“This is my brother,” he presented the man, “and so these are the three young men who have worked so hard to solve the mystery of my crash into the lake!” He shook hands and they selected a private dining room on the second floor for a midnight repast.

“Well,” he said, smiling pleasantly at the three rather silent youths as the first course, a hot, nourishing soup, was served, “have you solved the puzzle of the mystery crash?”

“I think we have—but not all, sir,” replied Bob. “I think I can put together what happened, but not why it had to happen.”

“Well, sir,” Bob, without trying to be vain, spoke frankly. “We got mixed up and puzzled, at first, because we were trying to solve a lot of things by connecting them with your—disappearance.”

“That mixed Griff’s case in, and his father’s,” agreed Curt, and he turned back to give Bob the center of the stage.

“You didn’t know whether the damage to airplanes was aimed at the plant or at you direct,” Bob told Mr. Tredway, who nodded. “You had two airplanes—both alike, except one was the Golden Dart and the other was the Silver Flash.”

“Exactly. And I thought,” Mr. Tredway interrupted, “if the guilty person knew which airplane I meant to deliver, he would damage that one and so, at the last minute I changed my ship, after saying I was going to deliver the Golden Dart I took off in the Silver Flash——”

“And you were right,” gasped Al. “When we flew the Golden one her rudder cable was frayed and broke.”

Mr. Tredway looked to Bob for an explanation, desiring to test the youth’s skill at deduction.

“I haven’t much to work on,” Bob said modestly, “but this is how I think you did it:

“Your brother flew here in the brown ship and hid it in the field, leaving the note to show you it was ready.”

“You took off early, and then set down the big cabin ship on the turf—that accounts for the deep ruts—and the ship was in the way so you dragged it into the stubble until the brown ship got up, then took the cabin craft into the air——”

“I fail to see what the brown airplane, and Arthur’s brother, have to do with it,” Barney broke in.

“Mr. Tredway’s brother had to be there to bring down the cabin ‘plane,” Bob explained. “At least that’s the only way I can see for the tracks in the field, and the crack-up, to fit the conditions,” he paused.

“You mean—they exchanged ships? Arthur landed the cabin crate and then flew away in the brown one, while his brother crashed the Silver Flash?” Barney demanded. Tredway nodded as did his brother.

“The young man is correct in his deduction,” the latter said. “I had to come and exchange ships with my brother and then crack up the Silver Flash to give the idea that its pilot—and my brother had taken off in it!—had gone into a mudhole or under rocks in the lake.”

“Removing one partner,” Mr. Tredway smiled, “gave the other one ‘a free hand’ if he was in any way guilty, or you, Barney!”

“No, I did not suspect you, I only wanted to get away and see what happened, and who did it.”

“These young men have cleared most of us,” stated Mr. Parsons. “They have done more! They know how the good parts are taken and cheap ones are substituted.” He explained about the trucks.

“But we can’t solve the mystery of why you brought books here and then said the company books were all at the plant,” argued Al.

“I found a small set of duplicate books—that is, what we would call ‘fake’ books—private books in the cabinet,” began Mr. Parsons.

“That’s where I took them from. You see, Barney, as long as we all suspected each other it was wisest for me to check them. Not that I accuse you, because they were in your desk. You were checking up, also, of course.”

“I’m not finished either,” declared Barney. “But—as long as Arthur wanted a look at them, it’s all right with me.”

“We have them safe,” said Curt. “And the brother is the mysterious man with the dark beard whose motorcycle Griff used, and it was he who was in the supply room, the other night.”

“I was,” said Mr. Tredway’s brother. “I came, with his key, got in the private gate, went up the fire escape and down to check up in the supply room—until Griff, running off with my motorcycle, made me suspicious, scared and anxious. So I left.”

“And I came here to see Arthur’s brother,” said Mr. Parsons, and Griff, looking ashamed added, “—and I ran away!”

“But we don’t know who damaged the crates, or if it was against Mr. Tredway or just spite work against the company,” Al said. “The mystery crash has failed to bring that to light.”

“Yes,” Barney suddenly leaned forward, “I’ve got to go, out and dismiss my taxicab—it’s eating its head off—but first I’ll give you a hint to chew over while I’m away.”

“Suppose the motive was revenge,” Barney spoke very low, and Bob, watching some curtains, at a locked side door, thought the breeze must be stirring them, “suppose there was once a pilot at the plant and that Arthur had to fire him and——”

“You don’t mean to say!—” Mr. Tredway bent close, excited. “The pilot I once discharged? Why—he’s the owner of this place. I’d never dream——”

“All the same—chew it over!” Barney rose. “I suppose you’ll be flying back—you won’t stay here tonight.” Tredway shook his head.

“Be right back,” Barney said. Bob, as the others chatted softly and excitedly, followed the departing manager with his eyes. He had thrown suspicion on several, had Barney. Also, he had been the only one who inspected and then reported on the Silver Flash, that nothing had been found tampered with! And—he had chased Lang and Bob to see Bob’s detective father! What a lot of curious facts, Bob mused!

“I think it would be a good idea for all of us to stay,” suggested Mr. Parsons. “It’s after midnight, and these lads must be worn out, with all their pedaling to and fro. We can telephone their homes.”

“You may all stay,” said Mr. Tredway. “But until we prove something I shall keep out of sight. Especially if the ex-pilot is apt to be around. I’m going to warm up my brother’s airplane and hop back to the airport I came from.”

They all parted. Curt declared he wanted to secure his forgotten bicycle, Bob and Al were sure they had better go on home if Mr. Parsons would let them take the taxicab. He decided that, after all, he and his son had better go home. The meal was finished. Mr. Tredway, going by a side hall, and down back stairs, sought to avoid recognition while his brother agreed to watch the ex-pilot at every chance.

Bob and Curt found the bicycle safe, and trundled it to the luggage rack at the back of the taxicab.

“Stay here,” he said, “I want to say something to Mr. Tredway—he’s warming up the airplane.”

As he reached the man so mysteriously lost and so suddenly discovered Bob caught his arm and spoke very earnestly.

“For the sake of your safety,” Bob whispered, “take off, just as you planned—but only go to the cornfield—set down as soon as you can—and then—look for—crossed wires!”

CHAPTER XXXI
“ONE MORE PROBLEM”

Bob did not delay a moment after he delivered his solemn warning to Mr. Tredway.

“Barney,” he said earnestly, “don’t stay here tonight! Come home with us. Stay with the Sky Squad.”

“You forgot where you were, didn’t you, when you spoke about the——” he lowered his voice, glanced around, spoke carefully, “—the ex-pilot as the one who had a motive for injuring Mr. Tredway?”

“I’m sure I heard something. You didn’t think, but there’s a curtained door in that private room we used. How do you know Jenks or—the other one—might not have heard you?”

“Lad, you’re quick! Right, too. Maybe I’d better go on. But I won’t need to stay with you.”

Barney, half-amused at Bob’s concern, and partly wondering what caused it and if he actually had been spied on, overheard, and realizing even better than did Bob, he thought, how dangerous such an accusation might be, Barney agreed.

The ride back to town was taken up with discussion of Barney’s hint but through all the talk Bob was rather quiet.

It was decided that the three members of the Sky Squad would be taken home first, then Griff and his father would go on, leaving Barney to finish the ride to his own home.

As the car drew up in front of Bob’s house and Al began saying his goodnight, quite sleepily, Bob turned to Mr. Parsons.

“What do you say to going back to the plant, after you drop Griff, and getting the real set of company books, and bringing them here. We can work on them together, and see if there is anything in the private set that doesn’t agree with the others.”

“Why not wait until morning?” suggested Mr. Parsons. “Aren’t you worn out?”

“What books?” Barney asked. “Oh—that’s so. I remember. You said you had them. Put them away carefully! Don’t leave them out.”

“Oh, we will,” agreed Al, overhearing. “We’ll put them in the big desk in Father’s study and lock them up.”

“Well, goodnight,” said Curt. He had been invited to stay but he preferred to go on home. Bob threw in a suggestion.

“At that,” he said, “Curt, why don’t you let me telephone your mother, and you stay. And Barney could wait with us till Mr. Parsons comes back.”

“Well, come to think of it, why not?” Barney decided. “If it won’t wake up your folks.” Bob assured him it wouldn’t. His mother must still be waiting up, he declared; there was a light burning in his father’s study.

“Good grief!” he cried, “I never thought—supposing Dad has come home?”

“Let’s go and see—will you come in with us?” he addressed Barney, and the latter cordially agreed.

“I guess we’d better let you wait in the living room till we see whether it’s Dad or Mother. She might not be dressed for company—if Mother is sitting up.” Barney agreed to wait, and Al went to the door to call Curt in to telephone home.

The den, into which Bob turned, closing the door quietly, was occupied, as he had all along suspected it would be, by his father.

“I heard that you weren’t in the other city,” Bob said, after a hasty greeting. His father saw his eagerness and let him talk. “Lang flew there to get help—” he sketched very swiftly the incidents of the night. “Now, Father, what brought you home? Have you?——”

“Not until tonight. But I know it’s the same person, and I’ve got him in the living room and I want to pretend to him that we are guarding him from some one else, while we keep guard to see that he doesn’t take fright and escape.”

“He came to a detective at the very first. He has put suspicion on everybody else. He seems terribly anxious about those books.”

“Circumstantial evidence justifying suspicion, but not proof. However—I’ve learned that some people, probably using assumed names—it may all be the same person—have been changing aircraft stock into gold. What is your plan, son?”

“We must keep him from guessing that we suspect—and keep him where we can watch him. The way I plan, if you agree, is this. Father, if he is the guilty one, he is terribly dangerous. He must have crossed wires on Mr. Tredway’s airplane, before the owner left the plant—hoping he’d have a short-circuit, set the gas on fire and come down in flames. Then he thought the Golden Dart was the cabin ship to be flown and he frayed the rudder cable. When he discovered the other ship was going he might have crossed wires on that—remember, he mentioned ‘crossed wires’ back in the other city? And he’s the only one who inspected the Silver Flash when she crashed and was hauled in. So we must keep him here where we can hold him if he makes a move.”

“Right. Get him in, son. We will pretend to study the books, and I will watch his reaction.”

“We will let him go. He cannot leave tonight because if he has been taking stock and exchanging it for gold, he probably had to bank it—he wouldn’t leave it in his house, would he, son?”

“We can have detectives watch his house all night. Father, fix it with the Chief of Police while I get him.”

Barney was ushered in, Al and Curt joined them and the three of the Sky Squad lined up on the davenport to watch Barney as the detective discussed the case.

Mr. Parsons, for whom Al watched to let him in without awakening Mrs. Wright, brought other books and they were all busy.

“We’ve solved one mystery—how the bad parts are coming in,” said Bob, confidently. “Curt, bring the false ledger and the real one.”

“Notice how those tiny pencil ‘ticks’ are made in the beginning of some entries?” Bob pointed to several. “There aren’t any in the regular ledger, but the entries correspond, and they are always worded in a queer way. See this one, about fabric: ‘10 bolts fabric, cotton, quality A—dash—X—one hundred,’” he quoted. “Now all the entries that are ticked in the false ledger are backward like that—and the same in the regular book, but no others except the ticked ones are!”

“Here are several bills of lading that weren’t entered Saturday, just slipped into the back of the regular ledger,” Bob drew them out and unfolded them. “One is all right, but the other is made out backward—the same as the ticked ones—and it isn’t a real bill of lading at all, because it is dated for today, and the shipment that arrived today isn’t to be delivered until tomorrow and we saw the two trucks exchanging goods on the byroad—or, Curt did.”

“This bill of lading being dated ahead and being one of the ‘backward wording’ sort, shows that those are the entries that are ‘queer.’ That solves the mystery, because we know how those things are being substituted tonight.”

“Then the bookkeeper is due for a call on the carpet—maybe worse,” said Barney. “That’s his book, and the false set is the same handwriting!”

“That settles that mystery and leaves only the one about Mr. Tredway’s possible evil wisher,” said Mr. Parsons.

“Why, that’s attended to—all we need to do is to watch that ex-pilot, and Mr. Tredway’s brother has agreed—” Al paused. The den private extension telephone was ringing.

“It’s for you, Bob,” his father said. “Who’d be—oh, Mr. Tredway! How are you? Glad you’re ‘alive and kicking.’ Yes, this is Wright. My son stole a march on me, finding you. Here he is.”

“Hello....” he said amid a tense silence. “Oh, did I guess right?... You didn’t go on? ... set down in the cornfield ... fix it in the morning?... Yes. Thank you, sir, for calling. Yes, we just got here.”

“Another of the puzzles solved, and I guessed rightly,” he said. “Barney, when you suspected the ex-pilot, I thought it might be that he’d do the same as he had done on the airplane I piloted—Mr. Tredway’s own sport craft. You know why I had to set it down?”

“No,” said Bob, slowly. “You mentioned the ex-pilot having access to the ‘planes. Well, on the brown ship—the wires were crossed tonight!”

“Oh!” Barney gasped, and recovered from his startled amazement. “You don’t say! That’s bad for—the ex-pilot.”

“But it disposes of one mystery—who! He was probably there at The Windsock and heard you—don’t you suppose?”

“All but one more puzzle,” said Curt. “Who’s getting away with the small parts, and valuable instruments?”

“I can settle that!” said Barney. “Sandy Jim, the rigger Al was put to work for—remember him sending you to his house with a lot of parcels supposed to contain junk for his kid?” Al nodded, dismayed. It hurt to hear that honest-looking Sandy was so wicked. But Barney seemed to have the correct idea, as the evidence indicated.

“We’ll round them up tomorrow.” Barney rose. “Suppose I take those books along with me? I’ll bring them in early in the morning.”

“Fine!” Bob jumped up, gathering the books. “There’s a Summer shower wetting the streets—I’ll wrap these in paper for you.”

When he returned with the parcel all goodnights had been said and the party broke up.

“But how can you? He has helped us, and he’s Mr. Tredway’s friend and I always thought—er——”

“A criminal had to have a motive?” prompted his father. “I attached no importance to one fact I have discovered, until I felt sure of Barney’s guilt. Now I do. This might be his motive! Years ago Mr. Tredway won the girl whom another pilot was courting. The man went from bad to worse, threatened—and then disappeared.”

“Of course that was not the pilot’s name. He must have changed his name as well as his appearance.”

“Then, Father, how did you know it’s Barney. How about the ex-pilot? Couldn’t he?——”

“Well—then—good cracky! Bob—you gave the culprit all the evidence in those books—to destroy!”

“No!” Bob smiled. “Dad’s encyclopedia is shy four volumes, and there are three vitamine books gone, and Barney has them. The real books are in their places on our shelves!”

CHAPTER XXXII
FLIGHT!

When the sun peered through dispersing Summer storm clouds it saw three alert, wide-awake youths, a little tired but very tense, in the testing field of the Tredway aircraft plant.

“Is Tredway’s speed plane fueled up,” Mr. Wright came over from the offices where he had deposited the company books in readiness for later use: his question was addressed to Griff.

“We’ve got a net spread that Barney Horton couldn’t escape if he was an eel. One of my best detectives has been outside his house ever since he went in from the taxi, at one ‘a.m.’ Those two men over by the offices, getting ready to dig a trench, are two picked men of my headquarters staff. Every motorcycle man, every traffic man, all our roundsmen and policemen are on the alert.”

“I simply cannot believe it of Barney,” Mr. Tredway was as doleful as though they were planning to arrest him, instead of his plant manager, “I took him in and gave him every opportunity, taught him all he knows, pushed him to the top. To think—”

“But he doesn’t look a bit like the man who was trying to win the woman who became my wife.”

“By the way,” interrupted the Chief of Police, “she hasn’t appeared at all in this—have you separated? Isn’t she——”

“Oh, yes,” quickly, “she is alive. My wife is away in Europe. That is the reason I decided to—disappear. I knew that news of it would not reach her before I ‘came to life.’”

“But if Barney is the guilty man,” Curt was still dazed, “why did he turn suspicion on that ex-pilot at The Windsock?”

“He tried to turn suspicion on everybody,” retorted Mr. Wright. “It is a favorite trick of a guilty person. He has practically accused the bookkeeper, the supply clerk, Sandy Jim, the rigger and the man you mentioned.”

“But he’s free,” Al spoke. “Why didn’t you arrest him while you had him at the house showing him the books?”

“You must remember one fact, my young ‘Sky Squadder,’” the Chief of Police commented. “Circumstantial evidence, and suspicion are one thing. Proof of guilt that will stand in court against a clever lawyer is something quite different.”

“In other words,” Mr. Wright explained, “we feel, with absolute conviction, that Barney is our man. We haven’t any actual proof. We must wait until he makes some open move. Bob, cleverly discovering Barney’s supposed guilt because he saw Barney make that excuse to get out to the airplane when he said he wanted to dismiss his taxi, did all he could to keep the man close to his Sky Squad; but Barney was clever.”

“I thought he would make a try for the books during the night if I got him to stay with us,” Bob admitted modestly. “Then, when he refused to spend the night with us I hoped he’d discover that we had substituted other books for the ledgers, and would try to get in our place to get all the incriminating evidence. But,” dejectedly, “he was too clever for that, even.”

“How do you expect him to make an open move, if he’s all that wise?” asked Griff.

“Well,” Mr. Wright spoke up, “some one has been quietly exchanging company stock, turning some into gold, here and there. I think it was Barney’s work under assumed names, to get his money into shape for escape. We have made him see that we know how the cheap, shoddy supplies are coming in, and other things: he will try to get away.”

“The paying tellers of the town banks are on the watch. The first minute he comes to close his accounts, as he will do before he takes a train, we will be informed. Before he goes he may try to destroy the false account books, and leave only conviction of his guilt, but no real, legal proof.”

“But—” Al was still somewhat puzzled. “Bob, how did you come to suspect Barney at all?”

“Do you remember me telling what was said when I flew with Lang to see Father?” As Al and Curt nodded, Bob added, “Barney used a phrase about ‘crossed wires.’ Then I found crossed wires in Mr. Tredway’s ship last night, and later Mr. Tredway found wires chafed, and led across each other, by his brown ‘plane carburetor. It was the quickest way to endanger a ship—the spark could set fire to free gas, and might not be noticed in daylight. Barney had time to do it.”

“When he went out? I see,” Curt said. “But, Bob, you thought some one was listening, watching—you told Barney so.”

“I still think some one was spying over our dinner—but it may have been the manager, Jenks, who may be ‘in’ with Barney.”

“Speak of the—” Mr. Tredway gave a warning glance as he began the old adage, “speak of the devil, he’s sure to appear.”

To their amazement, Barney came through the gates. He was calm, quiet, not at all furtive or frightened.

“What was the idea of that trick you played with the books?” He patted the package he carried. Bob was confused.

The arrival of the rigger, Sandy Jim, coming early to complete work on the new airplane for which the owner was in such a hurry, enabled Bob to hide his confusion as his father answered, quietly, “I’ll tell you that, Barney.”

Bob, who turned his head to hide his crimson face, and who went to greet Sandy Jim, with Al, as an excuse to avoid an explanation that might upset their plans, was surprised at the look on Sandy Jim’s face.

“Hello, Sandy!” Al greeted, taking the amazement as natural, since everyone around the plant supposed the owner to have gone under the mud in the Silver Flash, “ready for work early.”

Bob took over the explanation, giving Sandy enough of the former happenings to enable the rigger to recover from his surprise.

“I’m right glad,” the man stated, finally. “Now—Al, you get some of your crowd together and fuel up this new crate—soon as a pilot shows up we want it tested. I may have to make some changes in the wire tension and balance—get busy, me lads!”

Al eagerly agreed, seeing that their carefully planned “coup” had fallen through. Barney, listening to Mr. Wright, to Mr. Tredway, to the latter’s partner and the Chief of Police, trying, all together, to give him a “third degree,” began to laugh.

“That’s a good one!” He threw back his head, roaring his mirth. “So I’m the culprit, eh? Ho-ho! Oh, my, that’s rich. Clever Sky Squad you have, Wright! Ha-ha-ha-ho-ho! Here I am doing all I can to help my partner, trying to solve the puzzles he couldn’t untangle—and I’m to be arrested!”

“No one spoke of arrest!” the Police Chief hedged. “Are you sending some one else to get your banked gold?”

Barney stared and then smiled. “All the stock I ever had is in my safe deposit box—come on! I’ll show you, at the bank.”

They were puzzled. Arthur Tredway was eager to claim that his friend and protege was innocent.

The others were compelled to admit as Bob mentally decided, that Barney’s face, manner and actions were open and honest.

“That’s enough gas,” said the rigger. “Now, Al, fill her up with oil—I want to see Mr. Tredway.” He descended from the aircraft, went to his employer and with many protestations of delight gripped his hand.

“See here,” he urged, “Mr. Tredway, this crate they’re fueling is in a big rush. I have to make adjustments for balance before she is delivered. Can’t you take her up?”

“Why not?” Mr. Tredway was anxious to get into action since he had agreed to “return to life.”

Bob nodded, consulted the brand new instruments and noted that the fuel and oil registered at “full.”

His brother did his bidding. It took several trials to start the new engine but Bob got it going and then drew back the throttle to idling speed and went over to rejoin the group.

“I don’t think Arthur ought to take that crate up,” Barney was half laughing. “Of course I know that the only wires I ever crossed was when I flew my crates over telegraph lines—but he might think I had ’em crossed in this ship!”

“I’ll get the speedster of Mr. Tredway’s warmed up, too,” Bob said softly, “in case——”

To Al’s amazement and Curt’s astonishment the head of the Sky Squad beckoned furiously. They followed.

“See if there’s gas and oil in this,” he urged as he led them to the ship he had flown the night before, returned to its field by Mr. Parsons. “Listen, fellows——”

As he busied himself making ready to start the motor, getting the nose of the sport ‘plane into the wind, Bob explained.

“While Mr. Tredway was joking Barney about the crossed wires, did you see Jim’s face?”

As the engine took up its roar, he clambered in again, leaned far over the edge to Curt, while Al climbed into the after seat.

“Sandy Jim turned white,” he said above the engine hum. “I think we’ve found the real—watch, fellows! Father is going to tell Barney in front of Sandy Jim about the crossed wires.”

“Jim is acting nervous,” added Curt. “He’s turning—the chief has grabbed his arm. Now Dad is going to say to Barney that he’s guilty, that he hates his benefactor because of the other man winning Barney’s girl—of course we know it’s Jim, now—watch him! Jim’s being accused now—look!”

CHAPTER XXXIII
THE SKY SQUAD WINS

Roaring across the runway, Bob’s one purpose was to use the airplane as a missile, to run it into the other before Sandy Jim could rise. In that he failed. The other ship was up, and Bob knew that he had so much speed that he must take off or ram into a hangar.

By a spurt of the cold engine, risking a stall to get his trucks over the hangar, Bob soared.

Leveling off, he glanced around. To his amazement he saw Al snapping on his safety belt in the rear cockpit seat. Al waved a hand, pointing to one side. And Bob looked.

Bob began to climb. If he could force Jim to earth as he had been herded the night before—

But Bob sideslipped, dropped steeply into a dive to come out of the slip, and as he drew the ship to level flight, heard something strike the prop, saw it shatter.

Bob began to look for a way to spiral back to the testing field. His propeller, with a blade shattered, was useless.

Al screeched again. To the west, coming fast, was a ship they both recognized. Lang was returning in Griff’s speedster. Also, as Al pointed out, the cabin ‘plane was rising from the landing field.

Forestalled by the approach of Lang, with the other ship rising to chase, with his engine functioning badly, and the resulting distraction of attention, Jim’s safety was endangered.

The very thing that he had done when he planned to urge Mr. Tredway to test the ‘plane—crossing two wires—had prevented his escape.

The new carburetor, leaking, dripped a rich gas and air mixture onto the sparking wires—there was a flash of flames as Bob looked.

Almost he forgot his own purpose, but with steeled will he held his tight spiral, saw the cabin ship was out of his way, shot the field, and landed.

When Lang and the others joined him beside the smoking ruins of the new ship, they saw Sandy Jim, who had tried to escape by jumping before the flames reached him.

“I hated Tredway from the time he got the girl I wanted to marry,” Jim panted, as they gave him water. “I went from bad to worse—went to the dogs. I got in with tough men, tried prize-fighting, that’s how my face got changed, so I wasn’t easy to remember and recognize.

“Laid low for a while, then I gave up plans for revenge, and decided to come to work here to be close to the woman I loved, only, last Fall, she went away. So I knew Tredway had drove her to separate—”

“You’re crazy! My wife went to Europe for a long visit with relatives in France!”

“Honest? Then all my hate was on a wrong idea. Well, you know most of the rest. I damaged ships, worked with the bookkeeper and the supply clerk and a manager of The Windsock to substitute cheap stuff for good, sell the good and ruin the plant—but it was all no use—and started on a wrong idea—no use to say I’m sorry—but—well, boys, handle me easy—I’m no good, but I can feel pain!”

“I feel sorry for Jimmy-junior, and the man’s wife,” said Curt, after the ambulance had taken Sandy Jim to the hospital.

“Jimmy-junior isn’t his son,” explained Mr. Parsons. “He is the son of Sandy’s brother, whom Jim took to raise. It would be a good idea if you young men took him into the Sky Squad now, to take his mind off his sorrow.”

“Then let’s go,” urged Bob. “It’s just about time to wake up our new member.”

Transcriber’s Notes

*** END OF THE PROJECT GUTENBERG EBOOK THE MYSTERY CRASH ***

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The Project Gutenberg eBook of The Mystery Crash

THE
MYSTERY CRASH

CONTENTS

THE MYSTERY CRASH

CHAPTER I
THE DESERTED AIRPLANE

CHAPTER II
AT ROCKY LAKE

CHAPTER III
A GREATER MYSTERY

CHAPTER IV
THE SKY SQUAD IS FORMED

CHAPTER V
A DOUBLE PUZZLE

CHAPTER VI
SUSPICION AND SUSPENSE

CHAPTER VII
IN THE FALLING ’PLANE

CHAPTER VIII
WATCHFUL WAITING

CHAPTER IX
STRANGE ACTIONS

CHAPTER X
A SUMMONS

CHAPTER XI
A TRAIL AND A FLIGHT

CHAPTER XII
THE CHASE

CHAPTER XIII
THE DETECTIVE’S THEORY

CHAPTER XIV
THE SKY SQUAD DISOBEYS

CHAPTER XV
A TRIPLE TRAIL

CHAPTER XVI
THE “WINDSOCK”

CHAPTER XVII
“THE CASE IS ‘SEWED UP’”

CHAPTER XVIII
A NEW MYSTERY

CHAPTER XIX
TANGLED THREADS

CHAPTER XX
A PACKAGE OF MONEY

CHAPTER XXI
CAUGHT AND CLEARED!

CHAPTER XXII
THE “MYSTERY CRATE”

CHAPTER XXIII
BOB PURSUES!

CHAPTER XXIV
SUSPENSE!

CHAPTER XXV
CROSSED WIRES

CHAPTER XXVI
THE SKY SQUAD GOES INTO ACTION

CHAPTER XXVII
DRIVEN DOWN

CHAPTER XXVIII
CURT’S DISCOVERY

CHAPTER XXIX
A CONFESSION

CHAPTER XXX
BARNEY GIVES A HINT

CHAPTER XXXI
“ONE MORE PROBLEM”

CHAPTER XXXII
FLIGHT!

CHAPTER XXXIII
THE SKY SQUAD WINS

Transcriber’s Notes

THE FULL PROJECT GUTENBERG LICENSE

The Project Gutenberg eBook of The Mystery Crash

THE MYSTERY CRASH

CONTENTS

THE MYSTERY CRASH

CHAPTER I THE DESERTED AIRPLANE

CHAPTER II AT ROCKY LAKE

CHAPTER III A GREATER MYSTERY

CHAPTER IV THE SKY SQUAD IS FORMED

CHAPTER V A DOUBLE PUZZLE

CHAPTER VI SUSPICION AND SUSPENSE

CHAPTER VII IN THE FALLING ’PLANE

CHAPTER VIII WATCHFUL WAITING

CHAPTER IX STRANGE ACTIONS

CHAPTER X A SUMMONS

CHAPTER XI A TRAIL AND A FLIGHT

CHAPTER XII THE CHASE

CHAPTER XIII THE DETECTIVE’S THEORY

CHAPTER XIV THE SKY SQUAD DISOBEYS

CHAPTER XV A TRIPLE TRAIL

CHAPTER XVI THE “WINDSOCK”

CHAPTER XVII “THE CASE IS ‘SEWED UP’”

CHAPTER XVIII A NEW MYSTERY

CHAPTER XIX TANGLED THREADS

CHAPTER XX A PACKAGE OF MONEY

CHAPTER XXI CAUGHT AND CLEARED!

CHAPTER XXII THE “MYSTERY CRATE”

CHAPTER XXIII BOB PURSUES!

CHAPTER XXIV SUSPENSE!

CHAPTER XXV CROSSED WIRES

CHAPTER XXVI THE SKY SQUAD GOES INTO ACTION

CHAPTER XXVII DRIVEN DOWN

CHAPTER XXVIII CURT’S DISCOVERY

CHAPTER XXIX A CONFESSION

CHAPTER XXX BARNEY GIVES A HINT

CHAPTER XXXI “ONE MORE PROBLEM”

CHAPTER XXXII FLIGHT!

CHAPTER XXXIII THE SKY SQUAD WINS

Transcriber’s Notes

THE FULL PROJECT GUTENBERG LICENSE

THE
MYSTERY CRASH

CHAPTER I
THE DESERTED AIRPLANE

CHAPTER II
AT ROCKY LAKE

CHAPTER III
A GREATER MYSTERY

CHAPTER IV
THE SKY SQUAD IS FORMED

CHAPTER V
A DOUBLE PUZZLE

CHAPTER VI
SUSPICION AND SUSPENSE

CHAPTER VII
IN THE FALLING ’PLANE

CHAPTER VIII
WATCHFUL WAITING

CHAPTER IX
STRANGE ACTIONS

CHAPTER X
A SUMMONS

CHAPTER XI
A TRAIL AND A FLIGHT

CHAPTER XII
THE CHASE

CHAPTER XIII
THE DETECTIVE’S THEORY

CHAPTER XIV
THE SKY SQUAD DISOBEYS

CHAPTER XV
A TRIPLE TRAIL

CHAPTER XVI
THE “WINDSOCK”

CHAPTER XVII
“THE CASE IS ‘SEWED UP’”

CHAPTER XVIII
A NEW MYSTERY

CHAPTER XIX
TANGLED THREADS

CHAPTER XX
A PACKAGE OF MONEY

CHAPTER XXI
CAUGHT AND CLEARED!

CHAPTER XXII
THE “MYSTERY CRATE”

CHAPTER XXIII
BOB PURSUES!

CHAPTER XXIV
SUSPENSE!

CHAPTER XXV
CROSSED WIRES

CHAPTER XXVI
THE SKY SQUAD GOES INTO ACTION

CHAPTER XXVII
DRIVEN DOWN

CHAPTER XXVIII
CURT’S DISCOVERY

CHAPTER XXIX
A CONFESSION

CHAPTER XXX
BARNEY GIVES A HINT

CHAPTER XXXI
“ONE MORE PROBLEM”

CHAPTER XXXII
FLIGHT!

CHAPTER XXXIII
THE SKY SQUAD WINS