"Once more! Will you give me the recognition signal?"

The Great Dome on Mercury

By Arthur L. Zagat

D arl Thomas mopped the streams of perspiration from his bronzed face and lean-flanked, wiry body, nude save for clinging shorts and fiber sandals. "By the whirling rings of Saturn," he growled as he gazed disconsolately at his paper-strewn desk. "I'd like to have those directors of ITA here on Mercury for just one Earth-month. I'll bet they wouldn't be so particular about their quarterly reports after they'd sweated a half-ton or so of fat off their greasy bellies. 'Fuel consumption per man-hour.': Now what in blazes does that mean? Hey, Jim!" He swiveled his chair around to the serried bank of gauge-dials that was Jim Holcomb's especial charge, then sprang to his feet with a startled, "What's the matter?"

The chunky, red-haired control-man was tugging at a lever, his muscles bulging on arms and back, his face white-drawn and tense. "Look!" he grunted, and jerked a grim jaw at one of the dials. The long needle was moving rapidly to the right. "I can't hold the air pressure!"

"Wow, what a leak!" Darl started forward. "How's it below, in the mine?"

"Normal. It's the Dome air that's going!"

"Shoot on the smoke and I'll spot the hole. Quick, man!"

"Okay!"

Thomas' long legs shot him out of the headquarters tent. Just beyond the entrance flap was one of the two gyrocopters used for flying within the Dome. He leaped into the cockpit and drove home the starter-piston. The flier buzzed straight up, shooting for the misted roof.

T he Earthman fought to steady his craft against the hurricane wind, while his gray eyes swept the three-mile circle of the vault's base. He paled as he noted the fierce speed with which the white smoke-jets were being torn from the pipe provided for just such emergencies. His glance followed the terrific rush of the vapor. Big as a man's head, a hole glared high up on the Dome's inner surface. Feathered wisps of tell-tale vapor whisked through it at blurring speed.

"God, but the air's going fast," Darl groaned. The accident he had feared through all the months he had captained Earth's outpost on Mercury had come at last. The Dome's shell was pierced! A half-mile high, a mile across its circling base, the great inverted bowl was all that made it possible for man to defy the white hell of Mercury's surface. Outside was an airless vacuum, a waste quivering under the heat of a sun thrice the size it appears from Earth. The silvered exterior of the hemisphere shot back the terrific blaze; its quartz-covered network of latticed steel inclosed the air that all beings need to sustain life.

Darl tugged desperately at the control-stick, thrust the throttle over full measure. A little more of this swift outrush and the precious air would be gone. He caught a glimpse of the Dome floor beneath him and the shaft-door that gave entrance to the mine below. Down there, in underground tunnels whose steel-armored end-walls continued the Dome's protection below the surface, a horde of friendly Venusians were laboring. If the leak were not stopped in a few minutes that shaft door would blow in, and the mine air would whisk through the hole in its turn. Only the Dome would remain, a vast, rounded sepulcher, hiding beneath its curve the dead bodies of three Earthmen and the silent forms of their Venusian charges.

D arl's great chest labored as he strove to reach the danger spot. Invisible fingers seemed to be clamped about his throat. His eyes blurred. The gyrocopter was sluggish, dipped alarmingly when it should have darted, arrow-like, to its mark. With clenched teeth, the Terrestrian forced the whirling lifting vanes to the limit of their power. They bit into the fast thinning air with a muffled whine, raised the ship by feet that should have been yards.

By sheer will he forced his oxygen-starved faculties to function, and realized that he had reached the wall. He was drifting downward, the hole draining the Dome's air was five feet above him, beyond his reach. The driven vanes were powerless to stem the craft's fall.

One wing-tip scraped interlaced steel, a horizontal girder, part of the vault's mighty skeleton. Darl crawled along the wing, dragging with him a sheet of flexible quartzite. The metal foil sagged under him and slanted downward, trying like some animate thing to rid itself of the unwonted burden. He clutched the beam, hung by one leg and one arm as his craft slid out from beneath him. The void below dragged at him. He put forth a last tremendous spurt of effort.

Two thousand feet below, Jim Holcomb, dizzy and gasping, manipulated the controls frenziedly, his eyes fastened on the dropping pressure-gauge. From somewhere outside the tent a dull thud sounded. "Crashed! Darl's crashed! It's all over!" Hope gone, only the instinct of duty held him to his post. But the gauge needle quivered, ceased its steady fall and began a slow rise. Jim stared uncomprehendingly at the dial, then, as the fact seeped in, staggered to the entrance. "That's better, a lot better," he exclaimed. "But, damn it, what was that crash?"

T he headquarters tent was at one edge of the circular plain. Jim's bleary eyes followed the springing arch of a vertical girder, up and up, to where it curved inward to the space ship landing lock that hung suspended from the center of the vaulted roof. Within that bulge, at the very apex, was the little conning-tower, with its peri-telescope, its arsenal of ray-guns and its huge beam-thrower that was the Dome's only means of defense against an attack from space. Jim's gaze flickered down again, wandered across the brown plain, past the long rows of canvas barracks and the derrick-like shaft-head. Hard by the further wall a crumpled white heap lay huddled.

"My God! It was his plane!" The burly Earthman sobbed as his ten-foot leaps carried him toward the wreck.

Darl was his friend as well as Chief, and together they had served the Interplanetary Trading Association, ITA, for years, working and fighting together in the wilds of the outer worlds. A thought struck him, even as he ran. "What in th' name o' Jupiter's nine moons stopped th' leak?" He glanced up, halted, his mouth open in amazement. "Well, I'm a four-tailed, horn-headed Plutonian if there ain't th' boy himself!"

Far up in the interlaced steel of the framework, so high that to his staring comrade he seemed a naked doll, Darl stood outstretched on a level beam, his tiny arms holding a minute square against the wall. Lucky it was that he was so tall and his arms so long. For the saving plate just lapped the upper rim of the hole, and stemmed the fierce current by only a half-inch margin.

T he throbbing atmosphere machine in the sub-surface engine-room was replacing the lost air rapidly, and now the increasing pressure was strong enough to hold the translucent sheet against the wall by its own force. Jim saw the extended arms drop away. The manikin waved down to him, then turned to the shell again, as if to examine the emergency repair. For a moment Darl stood thus, then he was running along the girder, was climbing, ape-like, along a latticed beam that curved up and in, to swing down and merge with the bulge of the air-lock's wall.

"Like a bloomin' monkey! Can't he wait till I get him down with th' spare plane?"

But Darl wasn't thinking of coming down. Something he had seen through the translucent repair sheet was sending him to the look-out tower within the air-lock. Hand over hand he swung, tiny above that vast immensity of space. In his forehead a pulse still jumped as his heart hurried new oxygen to thirsty cells. He held his gaze steadily to the roof. A moment's vertigo, a grip missed by the sixteenth of an inch, the slightest failure in the perfect team-play of eye and brain, and rippling muscle, and he would crash, a half mile beneath, against hard rock.

At last he reached the curving side of the landing lock. But the platform at the manhole entrance jutted diagonally below him, fifteen feet down and twelve along the bellying curve. Darl measured the angle with a glance as he hung outstretched, then his body became a human pendulum over the sheer void. Back and forth, back and forth he swung, then, suddenly, his grasp loosened and a white arc flashed through the air.

Breathless, Jim saw the far-off figure flick across the chasm toward the jutting platform. He saw Darl strike its edge, bit his lip as his friend teetered on the rim and swayed slowly outward. Then Darl found his balance. An imperative gesture sent the watcher back to his post, his sorrel-topped head shaking slowly in wonderment.

D arl Thomas ran headlong up the staircase that spiralled through the dim cavern. "No mistake about it," he muttered. "I saw something moving outside that hole. Two little leaks before, and now this big one. There's something a lot off-color going on around here."

Quickly he reached the little room at the summit. He flung the canvas cover from the peri-telescope screen. Tempered by filters as it was the blaze of light from outside hit him like a physical blow. He adjusted the aperture and beat eagerly over the view-table.

Vacation jaunts and travel view-casts have made the moon's landscape familiar to all. Very similar was the scene Darl scanned, save that the barren expanse, pitted and scarred like Luna's, glowed almost liquid under the beating flame of a giant sun that flared in a black sky. Soundless, airless, lifeless, the tumbled plain stretched to a jagged horizon.

The Earthman depressed the instrument's eye, and the silvered outside of the Dome, aflame with intolerable light, swept on to the screen disk. The great mirror seemed alive with radiant heat as it shot back the sun's withering darts. The torrid temperature of the oven within, unendurable save to such veterans of the far planets as Darl and Jim Holcomb, was conveyed to it through the ground itself. The direct rays of the sun, nearer by fifty million miles than it is to Earth, would have blasted them, unprotected, to flaked carbon in an eye-blink.

An exclamation burst from Darl. A half-inch from the Dome's blazing arc, a hundred yards in actuality, the screen showed a black fleck, moving across the waste! Darl quickly threw in the full-power lens, and the image leaped life-size across the table. The black fleck was the shadow of a space-suited figure that lumbered slowly through the viscous, clinging footing. How came this living form, clad in gleaming silver, out there in that blast-furnace heat? In one of the space suit's claw-like hands a tube flashed greenly.

D arl's hand shot out to the trigger of the beam-thrower. Aimed by the telescope's adjustment, the ray that could disintegrate a giant space flier utterly flared out at his finger's pressure. Against the lambent brown a spot glowed red where the beam struck. But, warned by some uncanny prescience, the trespasser leaped aside in the instant between Thomas' thought and act. Before Darl could aim and fire again the foe had dodged back and was protected by the curve of the Dome itself.

Two white spots showed on either side of Darl's nostrils. His mouth was a thin white slit, his eyes gray marbles. Standing against the wall beside him was a space suit, mirror-surfaced and double-walled against the planet's heat. In a few moments he was encased within it, had snatched a pocket ray-gun from the long rack, and was through the door to the auxiliary air-lock. The air soughed out in response to his swift thrust at a lever, a second door opened, and he was on the outside, reeling from the blast of that inferno of light and heat.

For a moment the Earthman was dazzled, despite the smoked quartz eye-pieces in his helmet. Then, as his eyes grew used to the glare, he saw, far below, the erect figure of the stranger. The man was standing still, waiting. His immobility, the calm confidence with which he stood there, was insolently challenging. Darl's rage flared higher at the sight.

S corning the ladder that curved along the Dome to the ground, he threw himself at the polished round side of the great hemisphere. With increasing speed he slid downward, the gleaming surface breaking only slightly the velocity of his fall. On Earth this would have been suicidal. Even here, where the pull of gravity was so much less, the feat was insanely reckless. But the heat-softened ground, the strength of his metal suit, brought Darl safely through.

He whirled to meet the expected onslaught of the interloper. The green tube was aimed straight at him! The Earthman started to bring his own weapon up when something exploded in his brain. There was a moment of blackness; then he was again clear-minded. But he could not move—not so much as the tiny twist of his wrist that would have brought his own weapon into play.

Frozen by this strange paralysis, Darl Thomas saw the giant figure approach. The apparition bent and slung him to its shoulder. Glowing walls rose about him, dimmed. The Terrestrian knew that he was being carried down into one of the myriad openings that honeycombed the terrain. The luminescence died; there was no longer light enough to penetrate to his helmet's darkened goggles.

Frantic questions surged through the captured Earthman's mind. Who was his captor? From where, and how, had he come to Mercury? Jim, Angus McDermott, and himself were the only Terrestrians on the planet; of that he was certain. Only one or two of the reptile-skinned Venusian laborers had sufficient intelligence to manipulate a space suit, and they were unquestionably loyal.

This individual was a giant who towered far above Darl's own six feet. The Mercurian natives—he had seen them when ITA's expedition had cleaned out the burrows beneath the Dome and sealed them up—were midgets, the tallest not more than two feet in height. Whatever he was, why was the stranger trying to destroy the Dome? Apparently Thomas himself was not to be killed offhand: the jolting journey was continuing interminably. With enforced patience the Earthman resigned himself to wait for the next scene in this strange drama.

I n the headquarters tent Jim's usual grin was absent as he moved restlessly among the switches and levers that concentrated control of all the Dome's complex machinery. "Darl's been gone a devilish long time," he muttered to himself. "Here it's almost time for shifts to change and he's not back yet."

A bell clanged, somewhere up in the mass of cables that rose from the control board. For the next ten minutes Holcomb had no time for worry as he rapidly manipulated the innumerable wheels and handles in accord with the vari-colored lights that flickered on a huge ground-glass map of the sub-Mercurian passages. On the plain outside there was a vast rustling, a many-voiced twittering and squeaking that was not quite bird-like in tone. Through the opened tent-flap one could see the stream of Venusian workers, their work-period ended, pouring out of the shaft-head and filing between the ordered ranks of others whose labors were about to begin.

They were queer-looking specimens, these gentle, willing allies of the Earthmen. Their home planet is a place of ever-clouded skies and constant torrential rains. And so the Venusians were amphibians, web-footed, fish-faced, their skin a green covering of horny scales that shed water and turned the sharp thorns of their native jungles. When intrepid explorers discovered in the mazes of Mercury's spongy interior the surta that was so badly needed as a base material for synthetic food to supply Earth's famine-threatened population, it was to these loyal and amiable beings that ITA's engineers turned for workers who could endure the stifling heat of the underground workings.

The tent-flap was thrust aside, and a hawk-nosed Scot came sleepily in, to be enthusiastically greeted by Jim.

"Hello, you old Caledonian. 'Bout time you showed up."

T he newcomer fixed the speaker with a dour gaze. "An' why should I commence my tour o' dooty befair the time?"

"Because your chief, Mr. Darl Thomas, decided that he's a filliloo bird or somethin', flew to his little nest up top, an' forgot to come down again."

"Is this ain o' your jests, James Holcomb? I eenquire mairly that I may ken when to laugh."

"It's no joke, Mac. Last I see o' him he's skippin' around the roof like he has a buzzin' propeller stuck to his shoulder blades. He lights on th' air-lock platform, pops inside, an' goes dead for all I know."

From his bony legs to his scrawny neck the Scotchman's angular body, as nearly nude as that of the others, radiated the doubt that was expressed in every seam and wrinkle of his hatchet face.

"That's straight, Angus, may I kiss a pink-eared vanta if it ain't. Here's what happened." The bantering grin disappeared from Jim's countenance as he detailed the events that had preceded Darl's vanishing. "That was two hours ago," he concluded, "and I've been getting pretty uneasy about him."

"Why did na ye call me, so that ain o' us micht eenvestigate?"

"Hell. Darl wasn't born yesterday, he can take care of himself. Besides, your last shift was pretty strenuous, an' I thought I'd let you sleep. No tellin' what might happen next; this forsaken place has been givin' me the jim-jams lately."

"Your conseederation is touching, but—" A scratching at the door, accompanied by a high squeak, interrupted him.

T o Jim's shouted "Come in," there entered a Venusian, whose red rosette fastened to the green scales of his skin marked him an overseer. In the thread-like fingers of his hand he held a time-sheet, but the nervous pulsing of his gill-membranes caused Holcomb to exclaim anxiously: "What's wrong, Ran-los? No accident, I hope?"

The shrill combination of squeaks and twitterings that came from the man-reptile's toothless mouth meant nothing to the Scot, but Jim's last service had been on Venus and he had gained a working knowledge of the language. Finally the interchange was ended, and Ran-los bowed himself out. Jim turned to his companion.

"There's some more queer stuff for you, Angie. Just before shift-change, Ran-los heard odd sounds from the other side of the barrier at the end of gallery M-39. Says they seemed like signals o' some kind. He's a wise old bird and if he's worried about something it's damn well worth lookin' into. I don't know whether to find out first what's happened to Darl, or—"

Again there was an interruption; this time from the usually silent radio-communication set in the far corner. Jim leaped to the instrument and snapped on the head-set. Angus leaned over him, watching his intent face.

Faintly, as from an immense distance, came the thin whistle of space-radio. "S-W-A ... S-W-A ... S-W-A...." The general attention signal for all Earth's far-flung outposts from Jupiter to Mercury! The signal was coming from "M-I-T-A," the Earth company's home station on the Moon, outside the Heaviside layer. "S-W-A ... S-W-A ... M-I-T-A ... M-I-T-A." Again the signal rose and fell.

J im reached for the sending key and pounded out his acknowledgement: "K; M-E-R ... K; M-E-R ... K; M-E-R." He listened again, heard Venus answer, and Jupiter. Across five hundred million miles of space ITA men were responding to the roll-call of Earth. A reminiscent smile crossed Jim's face as he recognized the stuttering fist of Rade Perrin, on Eros. Rade always sent as if he were afraid the instrument would snap at his fingers.

M-I-T-A was signalling again, and now came the message: "S-W-A. All trading posts, mines and colonies are warned to prepare for possible attack. The Earth Government has just announced the receipt of an ultimatum from—" A raucous howl cut across the message and drowned it out. The siren blast howled on and on, mocking Jim's straining ears. "Well I'll be—Interference! Deliberate blanketing! The rats! The—" He blazed into a torrent of profanity whose imaginativeness was matched only by its virulence.

Mac was clutching his shoulder, stirred for once out of his vaunted "deegnity." "What is it, mon, what is it?"

"War, you bloody Scotchman, war! That's what it is!"

"War! Foosh, man, 'tis eempossible!"

"The hell it's impossible! Damn, and Darl not here! Take over, Mac; I've got to go up an' get him!"

I n the meantime Thomas' helpless journey had come to an end. After an interminable descent in what to him had been pitch darkness, the giant who was carrying him halted. Darl had heard the whistling inrush of air into some lock, then the clanging of a door. He felt himself hurled to the ground. Fumbling hands tugged at him, drew off his space suit.

The dim light of the cavern, as the helmet was dragged from his head, hurt Darl's eyes. Salt sweat stung them. It was hot, hotter than the Dome, hot as it was in the surta mine, where only the nerveless Venusians could work for any length of time.

Darl struggled to focus his eyes on a blurred blue form that towered above him. He felt sharp claws scratch at him and realized that cords were being passed around his limp body. They cut tightly into his legs and his arms. Then he was staring at a tube in the hand of his captor. Its end glowed with a brilliant purple light, and he felt a flood of reawakened energy warm him. His head jerked up, he strained against the taut, strong fibers binding him. The paralysis was gone, but he was still helpless.

A husky, rumbling voice broke the silence. "I wouldn't struggle, Earthman, if I were you. Even should you get free I still have my ray-tube. And my little friends would ask nothing better than your body to play with."

Darl writhed to a sitting posture. Now he could see his mysterious abductor clearly. This eight-foot, blue-feathered individual, with curved beak and beady eyes glittering from his naked, repulsively wrinkled head, was a Martian! Despite the human shape of his body, despite his jointed limbs and thumbed hands, this denizen of the red planet resembled a vulture far more than he did any other Earth creature.

T he Earthman's pride of race came to his rescue. "What's the game?" he growled. "Looking for trouble?" There was nothing in Darl's voice to show the fear that chilled him. Behind the Martian he could see vaguely a group of little yellow Mercurians.

"I'll ask all the questions here. And you'll answer them, too, if you're wise. Even your dull mind should comprehend that you are in my power."

Darl decided to proceed more cautiously. "What do you want from me?" he asked.

"I want," the Martian answered, "the recognition signal of Earth's space-ships."

"What!" The ejaculation burst from Darl's throat. This alien wanted the secret code, the watch-word that distinguished Earth's space ships, that gained for them free admittance to ITA's armed posts on the outer planets! This could mean only one thing, that the long rivalry, the ancient dispute between Earth and Mars was about to flare into open war. Any friendly visit from a foreign flier would be heralded by word from M-I-T-A. Thomas' face became a stony mask, covering the tumult of his mind.

"You understood. I want the Earth recognition signal at once—and after that, the surrender of the Dome." The very calmness of the husky tones was a threat.

"Never!"

"I warn you, Darl Thomas. It would be the better part of wisdom for you to yield willingly what I ask. You will give in eventually, and the means of persuasion I shall use will not be exactly—pleasant."

"You'll get nothing from me!"

The outlander's lidless eyes were filmed with a gray membrane. His head thrust forward, the feathered ruff beneath it bristled. Darl braced himself to withstand the swooping pounce that seemed imminent, the slash of the sharp beak. A burring rattle broke the momentary hush. The Martian relaxed, turned to the Mercurian from whom the sound had come and replied with staccato vibrance.

A s the cave filled with a whirring tumult Darl had a chance to examine the Mercurian natives crowding around his prostrate body. They were little yellow midgets, ranging from eighteen inches to two feet in height. Half of their small stature was taken up by snouted heads, with saucer-like, crimson eyes, and long white tusks jutting from foam-flecked mouths. The trunks were globular. The spindling legs and thin arms ended in sharp claws. There was an impression of animal ferocity about these tiny beings that stamped them as utter savages.

His captor was speaking to the Earthman again, his horny beak parted in what might have been a grim smile. "My friends remind me that I promised you to them. They have not forgotten how you and your fellows drove them from their burrows."

Darl was suddenly cold, though the sweat still streamed from his bound body. An uncontrollable shudder took him as he saw what the diminutive claws of the midgets held. While the Dome was still an unfinished framework one of the Terrestrian artisans had somehow been isolated from his fellows. Thomas had been of the party that found what was left of him, and the memory was still a throbbing nightmare.

"Once more! Will you give me the recognition signal?"

Darl shook his head, and prayed for sudden death. The Martian spoke to the dwarfs. They started forward, saliva drooling from their tusks. Darl gritted his teeth. He would hold out as long as was humanly possible.

A shrill rhythmic whistle came from somewhere outside. The blue giant started and snapped something to the Mercurians. Then he turned to Darl. "I must leave you for a little while," he said. "You have till I return to change your mind." With a parting admonition to the savages he was gone through a side door that Thomas had not noticed before.

G rateful for the postponement, however short, of the inescapable ordeal, Darl took stock of his situation. He lay, firmly bound, on the gritty rock floor of a low-ceiled cave about twelve feet square. In one wall was a door of red metal. The portal through which the Martian had vanished was next to it. Darl repressed an exclamation when he saw the opposite wall. It was of solid metal, bluishly iridescent. That was beryllium steel, the alloy from which the barriers at the terminals of the surta mine were fashioned. He forced his head higher. There were the marks of the jointures, the weldings that he himself had made.

The discovery seemed only to emphasize the helplessness of his predicament. His faithful Venusians, Ran-los, Ta-ira, and the rest were just on the other side of the three-inch plate of toughened steel. Three inches—yet it might have been as many hundred miles for all the help they could give him.

The yellow pigmies were circling in a macabre dance, their crimson eyes turned always toward him, hate glowing from their crawling depths. The whistle beyond changed in character. Darl recognized it. It was a Martian space-radio, the code of which Earth scientists had never been able to decipher. The Mercurian circle tightened, the fetid smell of the dwarfs was overpowering. Low at first, then louder and louder came the rattling cacophony of their chant. It filled the confined space with an overpowering clamor.

Darl writhed again, rolling over and over till he had reached the barrier. The pigmies gave way before him; evidently they had been warned to keep their claws off. With his insteps Thomas could reach the helmet of his space suit, where it had been dropped against the wall. He drove it against the metal and the clangor of its striking reverberated through the chamber. Darl managed to regulate the sound. He was now hammering out double knocks, long and short, spaced in the dots and dashes of the Morse code. "H-E-L-P D-A-R-L H-E-L-P D-A-R-L H-E-L-P...."

It was like some scene out of a madman's dream, this dim-lit cavern with its circling, dancing pigmies, the human figure lying sidewise on the ground, the rattling, savage chant and the metallic tattoo of Darl's hopeless message. A diabolic orgy of weird sound and crisscrossing shadows.

I t seemed hours that he pounded the helmet against the wall, hoping that the sound of it would be audible above the clamor of the midgets. His knees and hips were aching and numb, his leg ripped, almost to the bone by the sharp edges of the jagged floor. A sudden thought struck him. The fiber thongs that bound him were also rubbing against the rock. His flesh was terribly torn. Perhaps the thongs, too, had been frayed, weakened by the long continued friction.

He stopped the pounding signals and began to force his knees apart with all the power of his burly calves. The cords cut into his bulging muscles, cut into and through his skin. The veins stood out on his forehead, his neck was a corded pillar, his teeth bit through his lip as he stifled a scream of pain. Then, startlingly, the fibers snapped. His legs at least were free! He could fight, die fighting, and take these others with him into oblivion!

Darl leaped to his feet. Before the astounded natives realized what was up he was charging into their circle. A well aimed kick sent one crashing against the further wall. Another crunched against the rock. Then they were on him, a frothing wave of tiny furies. A score or more, they swarmed over him as a pack of African wild dogs swarms over a huge water-buffalo marked for the kill. Their claws scratched and tore, their sharp fangs stabbed into his flesh. His arms were still tightly bound to his sides, and he lashed out with his sandaled feet, swung his shoulders like battering rams, whirled in a dervish dance. Their brittle bones cracked under his hammer blows. They dropped from him like squashed flies. But, small as they were, he was terrifically outnumbered. By sheer weight of numbers they dragged him down, and piled on top of him as he lay, quivering and half-conscious, on the blood-soaked floor.

T hrough the blackness that welled and burst in his brain, one thought held. He had fooled the Martian, for in another instant the enraged savages, would kill him and the password to Earth's outposts would be safe. Already, he felt their fangs at his throat.

A whirring rattle cut through the turmoil like a whip-lash, and the heap of pigmies swiftly scattered. The man-bird from Mars was in the room. To Darl he was a blurred blueness from which glittered those two jet beads of eyes. As from a distance he heard a rumble, its meaning beating dully to him. "Not so easy, Thomas, not so easy. I want that signal, and by Tana, I'm going to have it."

The Earthman felt a current of cooler air. Instinctively he drew it into his lungs. It swept him up from the blackness that was closing in about him, brought him back to consciousness and despair. The chattering Mercurians crowded round to commence their interrupted orgy. "For the last time, Earthman, will you talk?"

Darl shook his head weakly and closed his eyes. In a moment—

Suddenly there was a crash of metal on metal. Another! The clangor of falling steel. Now someone was shouting, "Darl, Darl, are you alive?" All about him were shrill twitterings, squeaking calls, squeals and scutterings. Darl's nostrils stung with the odor of burned flesh. A door slammed....

He opened his eyes on a confused riot, saw Jim crouched, flashing ray-gun in hand. There was a hole in the barrier, and a mob of green-scaled Venusians were crowding through. Jim's ray caught the last Mercurian and the dwarf vanished in a cloud of acrid, greasy smoke.

"Thank God you've come!" Darl managed to gasp. Then cool blackness closed around him.

D arl Thomas lay on a cot in the headquarters tent, swathed from head to foot in an inch-thick wrapping of bandages. Jim's theory was that if one bandage was good, two were better, and he had cleaned out the post's slender stock. The red-haired Earthman was seated at the cot's side, watching the taciturn Scot operating the control board. He was telling Darl of the stirring message from M-I-T-A, and of the blanketing interference that marred the completion of the message.

"I didn't know what to do first," he continued, "whether to go down below and find out what Ran-los was battin' about, or shoot up to you in the connin' tower with the message. Like the thick-head I am, I picked the wrong thing. I sure got the gimmicks when I found the look-out empty, an' a space suit an' ray-gun gone." Jim grinned mirthlessly. "I was runnin' around in circles. You were outside, God alone knows how long. Believe me, I had you crossed off the list! That left two of us. With a war on, somebody had to stand guard in the look-out, the control board here had to be watched, an' somebody else had to get below.

"I was just tryin' to figure out a way o' cuttin' myself in half when I thought o' Ran-los. For a Weenie he's got a heck of a lot of sense. I zoomed down, hauled him out o' his bunk, scooted back up, showed him how to work the peri-telescope an' the big beam-thrower, an' left him there on guard."

"Best thing you could have done." Darl's voice was muffled by the bandages in which his head, as well as the rest of his body, was swathed. "He's got a head on his shoulders, that bird."

"Somethin' told me to take a ray-gun down in the mine with me. I was just steppin' out o' the elevator when I caught your last signal; -L-P D-A-R-L was all I got, but it was enough. How you ever got the other side of the barrier had me wingin', but you were there right enough, and yellin' for help. Ran-los had been doin' some repairs on a head support an' his weldin' machine was still there. Takin' an awful chance on there bein' air on the other side, I butted it up against the wall, shot the flame against the steel, and when she was soft enough had some of the Weenies smash her in with sledge-hammers. First thing I see is you, stretched out in a pool o' blood, with a couple of those yellow imps just gettin' to work on you. I clipped them first—that gave the Martian a chance to get away. An' then—well, you know the rest."

"I owe you one for that, Jim. Too bad, though, the big fellow escaped; we'll hear from him again, or I don't know the breed. Wonder how he got on the planet."

"The sucker must 'a' stowed away on the last recruit ship from Venus, slipped in a case o' tools or somethin'. Mars has labor agents there, too, you know, for their farms on Ganymede."

"Possibly. He knew my name, and that I was chief here. He's rigged up an air-lock out there, though I can't figure out how he gets the air."

"That's easy. While I was repairin' the barrier I found a pipe runnin' through. He's been stealin' ours. Which, by the same token, is why he was punchin' holes in the Dome rather than down below, where he would have been safer from discovery."

"So that's it. Get anything more on the space-radio?"

"Nope. Angus has kept the ear-flaps on, but the ether is still jammed. Hey, what're you up to?"

Darl was swinging his bandaged body up from the cot that had been set up in the headquarters tent at his insistence. "Can't lie on my back," he panted, "with that devil loose on the planet. Lord knows what he's up to now. We're short-handed enough as it is."

He rose to his feet, staggering with weakness and loss of blood. But his indomitable will drove him on. "I'll take over the control board. Send Angus up to relieve Ran-los, and you get below and speed up production. Earth will need double quantities of surta for food, now that there's a war on."

J im turned to convey the order to the Scot, but he whirled to the tent-flap instead as a riot of sound exploded outside. He tore aside the canvas, and now there was a burst of shrill, frightened Venusian cries, and a deeper, rattling chorus. Out on the Dome floor, pouring from the shaft-head in a panic torrent, came the Venusians. And among them, leaping, slashing, dragging them down, were countless little yellow men, their fangs and tusks and curving claws crimson with the blood of their victims.

"Darl, Mac, they've broken through! The Mercs have broken through!" The brown plain was a blood-spattered battlefield. Here and there little groups of the green men, braver than the rest, fought with spanner and hammer and whatever improvised weapon they may have found. "Come on, give 'em hell!" The three Earthmen dashed out, weapons in hand. But friend and foe were so intermingled that they could not use the devastating ray of their hand-guns. The fighting Venusians were vanishing under a tossing sea of yellow imps. And still the dwarfs poured forth from the mine entrance.

A blue form towered, far back, where all green had vanished, and only Mercurians were left. The Martian's beak opened in a rattling call. A group of hundreds of pigmies suddenly left the main fight, and came forward with short, swift steps. They dashed straight for the Earth trio and cut them off from the Venusians they were running to aid.

S ide by side the three fought. Their weapons grew hot in their hands as the beams cut great swaths in the seething ranks. The attackers halted, gave back, then surged forward again as the roar of their alien commander lashed them on.

The Earthmen faced the frenzied throng. A cleared circle was still around them. Beyond, the Venusians were all down. The Mercurian mob was closing in, the Terrestrians' rays had lost half their range. In moments now the ray-guns would be exhausted.

"The plane!" Darl shouted. "Back to the plane, it's our only chance."

The gyrocopter that could carry them aloft, out of the rout, was fifty feet away. They fought through to it and reached it just as the last faint charge flashed from Mac's tube. Jim was at the controls, Darl smashed his useless projector into the chattering face of a dwarf that had leaped on the Scot's shoulders and dragged Angus into the cockpit.

The overloaded flier zoomed to the landing at the lofty air-lock's manhole and hovered as Darl and Angus slipped home the hooks that held it to the platform. "The spy has the Dome," Jim grunted, "but by God, he hasn't got us. We'll be safe in the lock up here, till help comes. And then—"

"Safe is it?" Angus broke in. "Mon, luik ye what those bairns fra hell are up to the noo."

A yellow tide was rising about the base of each of the latticed steel arches that vaulted to the Earthmen's refuge. On every side the dwarfs were climbing, were swarming up the walls in numbers so great that they concealed the metal beneath. Up, up they came, slowly but surely. And right in the center of the plain, ankle-deep in the torn fragments of the murdered Venusians, was the Martian, directing the attack.

J im groaned. "I might've known he'd never let us get away. It's slow bells for us, I guess. Hey, where's Darl?"

"Gone weethin. No, guid losh, he's here!"

Darl appeared, his features pale and drawn, carrying an armful of ray-guns. "Grab these," he snapped. "We're not licked yet."

"Licked, hell!" Jim's roar reverberated. "We've just begun to fight!" The Scot was silent, but the battle light shone in his eyes. In another moment the Terrestrians were kneeling, were raking the roof girders as the mounting Mercurians came within range. Each had two ray-guns in his hands, and a little pile of extra tubes beside him. They fought silently, wasting not a single blast.

Six white rays flamed through the misty, humid air, and striking the teeming girders, swept them clean. A greasy, horrible smoke cloud gathered along the shell and drifted slowly down, till the concrete blocks from which the steel framework sprang were hidden in a black pall. Fighters, these three, true ITA men who had left memories of their battle-prowess on more than one wild planet! Gaunt-bodied demi-gods of war, they hurled crackling bolts of destruction from their perch at the Dome top. By hundreds, by thousands, the Mercurian pigmies vanished in dark vapor, or plunged, blackened corpses, into the fog that billowed below.

One by one the tubes were discharged and tossed down at the seething mob. The heaped weapons dwindled, and still the climbing hordes renewed themselves, came on in endless mounting streams to sure destruction. The open tunnel vomited forth a torrent of gibbering dwarfs. From the uttermost burrows of the planet the pigmies were flooding in at the call of the Martian who stood scatheless beneath and lashed them on with the strange dominance he held over them. The Earthmen fought on, endlessly, till they were sick of killing, nauseated with slaughter. And still the snouted, red-eyed imps came on.

J im snatched up his last two ray-guns. Out of the corner of his eye he noted that Darl was using but one, the other, his last, was thrust into the chief's belt. He wondered at this, but a new spurt of yellow above the oily fog wiped the question from his lips. "Swallow that, you filthy lice! Hope you like the way it tastes!" His guns spouted death.

"I'm through!" The call came at last from McDermott. "Me too!" Jim Holcomb hurled his final, futile tubes down at the blue figure of the Mars man. A moment's hush held the trio. Then Jim flexed his great hands. "Well, these'll take care of a couple more o' them before I check in."

"No you don't," Darl barked, his face a graven image. "Inside with you. The lock will hold 'em off."

"Yeah? Look."

Thomas swung in the direction Jim was pointing. Rising above the murk, something glinted in the pale light. On the furthest upright a clumped group of climbing savages were struggling to drag up one of the welding machines, a long black hose snaking from its cylindrical bulk.

"They'll cut through the steel in fifteen minutes with that. The bloody bugger ain't missin' a trick."

"Inside, I tell you." Darl's crisp tone of command brooked no denial. The three crowded into the cool recesses of the manmade aerie. Angus slammed the steel door shut. Even if by some miracle the Dome wall should be pierced and the air in the main vault dissipated into outer space, this air-tight compartment hung from the hemisphere's roof would remain, a last refuge, till the atmosphere within had become poisonous through the Earthmen's slow breathing. But the Martian had anticipated Darl's final move. The oxy-hydrogen jet of the welding machine the dwarfs were hoisting would make short work of their final defense.

F rom the conning-tower above Ran-los called excitedly. Through all the long battle the Venusian had remained steadfast at the peri-telescope, scanning the vacant terrain outside, and the heavens. As Darl and Jim dashed for the stairs Mac ran after them, crying out, "What did he say, mon?"

"Space ship in sight," Darl flung over his shoulder as he reached the upper landing.

"Praise be! Noo the haythan weel get his desairts!"

"Yeah, maybe—if it's an Earth ship. But we won't be here to see it."

Jim's red head was bending over the peri-telescope view-screen. "She's still thirty thousand miles away. Give her a speed of fifteen per second—she'll have to slow up to land, can't make it under forty-five minutes. By then we'll be in little pieces. It took me ten minutes to burn through the barrier when I rescued Darl, and it won't take the Mercs any longer to get at us."

Darl was very sober as he looked on with narrowed eyes. Against a background of velvet black, gold spangled, the slim space-traveler showed. The sun's rays caught her, and she was a tiny silver fish in the boundless void.

"Luik ye, mon, luik ye!" Angus, fairly dancing with excitement, elbowed Darl aside. "She's from Airth, richt enow!" At the nose of the oncoming flier a rapid succession of colored lights had flashed, the recognition signal that should give her safe access to the Dome. Again there was a coruscation of coded flashes. "She's a battle cruiser, what's mair!" the Scot exclaimed.

D arl sprang to the keyboard that manipulated the signal lights from the Dome's roof. "No use," he said, after a short while. "The Martian has cut off the current from the dynamos. I can't warn the ship." He made a hopeless gesture.

Jim looked at him wonderingly. "Warn 'em? What for? Even if we are all dead when she reaches here, at least she'll clean up the Mercs, and retake the Dome for Earth."

"Don't you see it? When the Mars man has once blasted his way in here and disposed of us, he'll be ready for the space ship. Her captain can't suspect anything wrong. He must have left Earth at the time of the ultimatum, and would easily get here before any ship could be sent out from Mars. He'll come on till he's within range of the beam-thrower, and the Martian will aim, press the trigger and the Earth ship and her crew of a half a thousand brave lads will be star-dust."

"Oh God!" Jim was white-faced. "Isn't there anything we can do? Maybe if he doesn't get our all-clear signal he'll sheer off." This was clutching at straws.

"Why should he? He must know how short-handed we are, and will simply think we're not on watch, or that our signal lights are out of order. Matter of fact, if he were at all suspicious he should be alternating his course right now—and he hasn't. Look."

Seemingly motionless, but really splitting the ether with terrific speed, the warship was coming straight on to garrison the beleaguered post. She had never wavered from her straight course for the Dome. The little group was silent, watching the help that was coming at last, coming too late.

F rom below there came a thunder of sound. Jim slid down the stairs. An irregular disk on the wall was glowing cherry-red from the heat of the blow-torch without, and the metal was quivering under the Mercurian's sledge-hammer blows. "Darl's right," he almost sobbed as he gazed helplessly. "They'll be through in no time. The Dome's gone, we're gone, the space ship's gone!"

"Let me pass, Jim." Thomas' quiet voice sounded behind him. Holcomb turned. His leader was in a space suit, the helmet still unfastened.

"Blazes! Where the devil are you going?"

"Here, cover me with this till I reach the gyrocopter, then get back quick, and seal the air-lock." Darl thrust into Jim's hand the ray-gun he had previously reserved. "There's only one way to kill off the Martian and his mob. I'm taking it."

Suddenly Jim Holcomb understood. "No, Darl, no—you can't do it! Not you! Let me go! I'm just a dumbhead. Let me go!"

"Thanks, Jimmy, but it's my place." Darl's voice was low, and very calm. "I was in charge, and I lost the Dome. If I can save the boys on the ship, and you two, it's the least I can do. Good-by, old man. Give my regards to Earth."

Thomas' face was gray-white. The thick bandages that still swathed him, Jim glimpsed them through the open neckpiece of the suit, gave him the semblance of a mummy. The helmet clicked shut. Swallowing a lump that rose in his throat, Jim pulled open the door. A wave of Mercurians surged in, to be seared into nothingness by his weapon. He was in the doorway, his ray sweeping the platform clear.

Darl was out now, stepping into the flier that still hung by its hooked moorings. Jim caught a flash of blue and looked up. The Martian was hanging to a girder just above, his green tube pointing straight at Darl. A white ray spurted from Jim's gun. The Martian's weapon and the hand that held it vanished in the sizzling blast. The plane was loose! Jim leaped inside the air-lock, slammed the steel door shut, clamped it, and sprang for the quartz peer-hole.

D arl's gyrocopter was diving on a long slant for the Dome wall. Faster and faster it went, till all Jim could see was a white streak in the smoky dimness. And now he could see the vast interior, the teeming plain, the dwarf-festooned girders and roof-beams. He stood rigid, waiting breathlessly. Then the plane struck—fair in the center of a great panel of quartz. The wall exploded in a burst of flying, shattered splinters. A deafening crash rocked the Dome.

Jim clung to his port-hole, tears rolling down his cheeks, unashamed. The plane, and Darl, vanished. Jim saw the black smoke masses whirl through the jagged hole in the Dome's wall as the air burst out in a cyclonic gust. He saw the vast space filled with falling Mercurians, saw a blue form plunge down and crash far below. He knew that in all that huge hemisphere, and in the burrows beneath it, there was no life save himself, and Angus, and the faithful Ran-los. For only in this compartment that clung to the roof of the Dome was there left air to breathe. And, from the void beyond, the silver space ship sped on toward Mercury, sped on to a safe landing that, but for Darl Thomas's sacrifice, would have been her doom....

Guided by Jim and Angus, a party of men from the battle-flier, equipped with oxygen respirators, went to the aid of Darl. They dug him out from under his crumpled plane and the piled splinters of quartz. His metal was dented and twisted, but unpierced. They carried him tenderly to the space ship, and carefully set him down. The ship's physician listened long with his stethoscope, then looked up and smiled.

"He's alive," the doctor said, "just barely alive. The thick padding of bandages must have saved him from the full shock of the crash. They're hard to kill, these ITA men. I'll be able to bring him around, God willing."