In ghostly, shivering streamers of green and blue, like northern lights, the closing hues of the fourth Hoderson symchromy, called "the Yggdrasil," shuddered down toward visual silence. Once more the ancient myth, antedating even the Dawn Civilization, had been told—of the tree of life with its roots in heaven and hell and the land of the frost giants, and serpents gnawing at those roots and the gods fighting to preserve it. Transmuted into significant color by Hoderson's genius, interpreted by the world's greatest color instrumentalists, the primeval legend of cosmic dread and rottenness and mystery, of wheels within cosmic wheels, had once more enthralled its beholders.

In the grip of an unearthly excitement, Thorn crouched forward, one hand jammed against the grassy earth beyond his outspread cloak. The lean wrist shook. It burst upon him, as never before, how the Yggdrasil legend paralleled the hypothesis which Clawly and he were going to present later this night to the World Executive Committee.

More roots of reality than one, all right, and worse than serpents gnawing, if that hypothesis were true.

And no gods to oppose them—only two fumbling, overmatched men.

Thorn stole a glance at the audience scattered across the hillside. The upturned faces of utopia's sane, healthy citizenry seemed bloodless and cruel and infinitely alien. Like masks. Thorn shuddered.

A dark, stooped figure slipped between him and Clawly. In the last dying upflare of the symchromy—the last wan lightning stroke as the storm called life departed from the universe—Thorn made out a majestic, ancient face shadowed by a black hood. Its age put him in mind of a fancy he had once heard someone advance, presumably in jest—that a few men of the Dawn Civilization's twentieth century had somehow secretly survived into the present. The stranger and Clawly seemed to be conversing in earnest, low-pitched whispers.

Thorn's inward excitement reached a peak. It was as if his mind had become a thin, taut membrane, against which, from the farthest reaches of infinity, beat unknown pulses. He seemed to sense the presence of stars beyond the stars, time-streams beyond time.

The symchromy closed. There began a long moment of complete blackness. Then—

Thorn sensed what could only be described as something from a region beyond the stars beyond the stars, from an existence beyond the time-streams beyond time. A blind but purposeful fumbling that for a moment closed on him and made him its agent.

No longer his to control, his hand stole sideways, touched some soft fabric, brushed along it with infinite delicacy, slipped beneath a layer of similar fabric, closed lightly on a round, hard, smooth something about as big as a hen's egg. Then his hand came swiftly back and thrust the something into his pocket.

Gentle groundlight flooded the hillside, though hardly touching the black false-sky above. The audience burst into applause. Cloaks were waved, making the hillside a crazy sea of color. Thorn blinked stupidly. Like a flimsy but brightly-painted screen switched abruptly into place, the scene around him cut off his vision of many-layered infinities. And the groping power that a moment before had commanded his movements, now vanished as suddenly as it had come, leaving him with the realization that he had just committed an utterly unmotivated, irrational theft.

He looked around. The old man in black was already striding toward the amphitheater's rim, threading his way between applauding groups. Thorn half-withdrew from his pocket the object he had stolen. It was about two inches in diameter and of a bafflingly gray texture, neither a gem, nor a metal, nor a stone, nor an egg, though faintly suggestive of all four.

It would be easy to run after the man, to say, "You dropped this." But he didn't.

The applause became patchy, erratic, surged up again as members of the orchestra began to emerge from the pit. There was a lot of confused activity in that direction. Shouts and laughter.

A familiar sardonic voice remarked, "Quite a gaudy show they put on. Though perhaps a bit too close for comfort to our business of the evening."

Thorn became aware that Clawly was studying him speculatively. He asked, "Who was that you were talking to?"

Clawly hesitated a moment. "A psychologist I consulted some months back when I had insomnia. You remember."

Thorn nodded vaguely, stood sunk in thought. Clawly prodded him out of it with, "It's late. There are quite a few arrangements to check, and we haven't much time."

Together they started up the hillside.

Especially as a pair, they presented a striking appearance—they were such a study in similarities and contrasts. Certainly they both seemed spiritually akin to some wilder and more troubled age than safe, satisfied, wholesome utopia. Clawly was a small man, but dapper and almost dancingly lithe, with gleamingly alert, subtle features. He might have been some Borgia or Medici from that dark, glittering, twisted core of the Dawn Civilization, when by modern standards mankind was more than half insane. He looked like a small, red-haired, devil-may-care satan, harnessed for good purposes.

Thorn, on the other hand, seemed like a somewhat disheveled and reckless saint, lured by evil. His tall, gaunt frame increased the illusion. He, too, would have fitted into that history-twisted black dawn, perhaps as a Savonarola or da Vinci.

In that age they might have been the bitterest and most vindictive of enemies, but it was obvious that in this they were the most unshakably loyal of friends.

One also sensed that more than friendship linked them. Some secret, shared purpose that demanded the utmost of their abilities and put upon their shoulders crushing responsibilities.

They looked tired. Clawly's features were too nervously mobile, Thorn's eyes too darkly circled, even allowing for the shadows cast by the groundlight, which waned as the false-sky faded, became ragged, showed the stars.

They reached the amphitheater's grassy rim, walked along a row of neatly piled flying togs with distinctive luminescent monograms, spotted their own. Already members of the audience were launching like bats into the summary darkness, filling it with the faint gusty hum of subtronic power, that basic force underlying electric, magnetic, and gravitational phenomena, that titan, potentially earth-destroying power, chained for human use.

As he climbed into his flying togs, Thorn kept looking around. False-sky and groundlight had both dissolved, opening a view to the far horizon, although a little weather, kept electronically at bay for the symchromy, was beginning to drift in—thin streamers of cloud. He felt as never before a poignancy in the beauty of utopia, because he knew as never before how near it might be to disaster, how closely it was pressed upon by alien infinities. There was something spectral about the grandeur of the lonely, softly-glowing skylons, lofty and distant as mountains, thrusting up from the dark rolling countryside. Those vertical, one-building cities of his people, focuses of communal activity, gleaming pegs sparsely studding the whole earth—the Mauve Z peering over the next hill, seeming to top it but actually miles away; beyond it the Gray Twins, linked by a fantastically delicate aerial bridge; off to the left the pearly finger of the Opal Cross; last, farther left, thirty miles away but jutting boldly above the curve of the earth, the mountainous Blue Lorraine—all these majestic skylons seemed to Thorn like the last pinnacles of some fairy city engulfed by a rising black tide. And the streams of flying men and women, with their softly winking identification lights, no more than fireflies doomed to drown.

His fingers adjusted the last fastening of his togs, paused there. Clawly only said, "Well?" but there was in that one word the sense of a leave-taking from all this beauty and comfort and safety—an ultimate embarkation.

They pulled down their visors. From their feelings, it might have been Mars toward which they launched themselves—a sullen ember halfway up the sky, even now being tentatively probed by the First Interplanetary Expedition. But their actual destination was the Opal Cross.

Suppressing the fatigue that surged up in him disconcertingly, Clawly rose to address the World Executive Committee. He found it less easy to suppress the feeling that had in part caused the surge of fatigue: the illusion that he was a charlatan seeking to persuade sane men of the truth of fabricated legends of the supernatural. His smile was characteristic of him—friendly, but faintly diabolic, mocking himself as well as others. Then the smile faded.

He summed up, "Well, gentlemen, you've heard the experts. And by now you've guessed why, with the exception of Thorn, they were asked to testify separately. Also, for better or worse"—he grimaced grayly—"you've guessed the astounding nature of the danger which Thorn and I believe over-hangs the world. You know what we want—the means for continuing our research on a vastly extended and accelerated scale, along with a program of confidential detective investigation throughout the world's citizenry. So nothing remains but to ask your verdict. There are a few points, however, which perhaps will bear stressing."

There was noncommittal silence in the Sky Room of the Opal Cross. It was a huge chamber and seemed no less huge because the ceiling was at present opaque—a great gray span arching from the World Map on the south wall to the Space Map on the north. Yet the few men gathered in an uneven horseshoe of armchairs near the center in no way suggested political leaders seeking a prestige-enhancing background for their deliberations, but rather a group of ordinary men who for various practical reasons had chosen to meet in a ballroom. Any other group than the World Executive Committee might just as well have reserved the Sky Room. Indeed, others had danced here earlier this night, as was mutely testified by a scattering of lost gloves, scarves, and slippers, along with half-emptied glasses and other flotsam of gaiety.

Yet in the faces of the gathered few there was apparent a wisdom and a penetrating understanding and a leisurely efficiency in action that it would have been hard to find the equal of, in any similar group in earlier times. And a good thing, thought Clawly, for what he was trying to convince them of was something not calculated to appeal to the intelligence of practical administrators—it was doubtful if any earlier culture would have granted him and Thorn any hearing at all.

He surveyed the faces unobtrusively, his dark glance flitting like a shadow, and was relieved to note that only in Conjerly's and perhaps Tempelmar's was a completely unfavorable reaction apparent. Firemoor, on the contrary, registered feverish and unquestioning belief, but that was to be expected in the volatile, easily-swayed chief of the Extraterrestrial Service—and a man who was Clawly's admiring friend. Firemoor was alone in this open expression of credulity. Chairman Shielding, whose opinion mattered most, looked on the whole skeptical and perhaps a shade disapproving; though that, fortunately, was the heavy-set man's normal expression.

The rest, reserving judgment, were watchful and attentive. With the unexpected exception of Thorn, who seemed scarcely to be listening, lost in some strange fatigued abstraction since he had finished making his report.

A still-wavering audience, Clawly decided. What he said now, and how he said it, would count heavily.

He touched a small box. Instantly some tens of thousands of pinpricks of green light twinkled from the World Map.

He said, "The nightmare-frequency for an average night a hundred years ago, as extrapolated from random samplings. Each dot—a bad dream. A dream bad enough to make the dreamer wake in fright."

Again he touched the box. The twinkling pattern changed slightly—there were different clusterings—but the total number of pinpricks seemed not to change.

"The same, for fifty years ago," he said. "Next—forty." Again there was merely a slight alteration in the grouping.

"And now—thirty." This time the total number of pinpricks seemed slightly to increase.

Clawly paused. He said, "I'd like to remind you, gentlemen, that Thorn proved conclusively that his method of sampling was not responsible for any changes in the frequency. He met all the objections you raised—that his subjects were reporting their dreams more fully, that he wasn't switching subjects often enough to avoid cultivating a nightmare-dreaming tendency, and so on."

Once more his hand moved toward the box. "Twenty-five." This time there was no arguing about the increase.

"Twenty."

"Fifteen."

"Ten."

"Five."

Each time the total greenness jumped, until now it was a general glow emanating from all the continental areas. Only the seas still showed widely scattered points, where men dreamed in supra- or sub-surface craft, and a few heavy clusters, where ocean-based skylons rose through the waves.

"And now, gentlemen, the present."

The evil radiance swamped the continents, reached out and touched the faces of the armchair observers.

"There you have it, gentlemen. A restful night in utopia," said Clawly quietly. The green glow unwholesomely emphasized his tired pallor and the creases of strain around eyes and mouth. He went on, "Of course it's obvious that if nightmares are as common as all that, you and yours can hardly have escaped. Each of you knows the answer to that question. As for myself—my nightly experiences provide one more small confirmation of Thorn's report."

He switched off the map. The carefully noncommittal faces turned back to him.

Clawly noted that the faint, creeping dawn-line on the World Map was hardly two hours away from the Opal Cross. He said, "I pass over the corroborating evidence—the slight steady decrease in average sleeping time, the increase in day sleeping and nocturnal social activity, the unprecedented growth of art and fiction dealing with supernatural terror, and so on—in order to emphasize as strongly as possible Thorn's secondary discovery: the similarity between the nightmare landscapes of his dreamers. A similarity so astonishing that, to me, the wonder is that it wasn't noticed sooner, though of course Thorn wasn't looking for it and he tells me that most of his earlier subjects were unable, or disinclined, to describe in detail the landscapes of their nightmares." He looked around. "Frankly, that similarity is unbelievable. I don't think even Thorn did full justice to it in the time he had for his report—you'd have to visit his offices, see his charts and dream-sketches, inspect his monumental tables of correlation. Think: hundreds of dreamers, to take only Thorn's samples, thousands of miles apart, and all of them dreaming—not the same nightmare, which might be explained by assuming telepathy or some subtle form of mass suggestion—but nightmares with the same landscape, the same general landscape. As if each dreamer were looking through a different window at a consistently distorted version of our own world. A dream world so real that when I recently suggested to Thorn he try to make a map of it, he did not dismiss my notion as nonsensical."

The absence of a stir among his listeners was more impressive than any stir could have been. Clawly noted that Conjerly's frown had deepened, become almost angry. He seemed about to speak, when Tempelmar casually forestalled him.

"I don't think telepathy can be counted out as an explanation," said the tall, long-featured, sleepy-eyed man. "It's still a purely hypothetic field—we don't know how it would operate. And there may have been contacts between Thorn's subjects that he didn't know about. They may have told each other their nightmares and so started a train of suggestion."

"I don't believe so," said Clawly slowly. "His precautions were thorough. Moreover, it wouldn't fit with the reluctance of the dreamers to describe their nightmares."

"Also," Tempelmar continued, "we still aren't a step nearer the underlying cause of the phenomenon. It might be anything—for instance, some unpredictable physiological effect of subtronic power, since it came into use about thirty years ago."

"Precisely," said Clawly. "And so for the present we'll leave it at that—vastly more frequent nightmares with strangely similar landscapes, cause unknown—while I"—he again gauged the position of the dawn-line—"while I hurry on to those matters which I consider the core of our case: the incidence of cryptic amnesia and delusions of nonrecognition. The latter first."

Again Conjerly seemed about to interrupt, and again something stopped him. Clawly got the impression it was a slight deterring movement from Tempelmar.

He touched the box. Some hundreds of yellow dots appeared on the World Map, a considerable portion of them in close clusters of two and three.

He said, "This time, remember, we can't go back any fifty years. These are such recent matters that there wasn't any hint of them even in last year's Report on the Psychological State of the World. As the experts agreed, we are dealing with an entirely new kind of mental disturbance. At least, no cases can be established prior to the last two years, which is the period covered by this projection."

He looked toward the map. "Each yellow dot is a case of delusions of nonrecognition. An otherwise normal individual fails to recognize a family member or friend, maintains in the face of all evidence that he is an alien and impostor—a frequent accusation, quite baseless, is that his place has been taken by an unknown identical twin. This delusion persists, attended by emotional disturbances of such magnitude that the sufferer seeks the services of a psychiatrist—in those cases we know about. With the psychiatrist's assistance, one of two adjustments is achieved: the delusions fade and the avowed alien is accepted as the true individual, or they persist and there is a separation—where husband and wife are involved, a divorce. In either case, the sufferer recovers completely.

"And now—cryptic amnesia. For a reason that will soon become apparent, I'll first switch off the other projection."

The yellow dots vanished, and in their place glowed a somewhat smaller number of violet pinpoints. These showed no tendency to form clusters.

"It is called cryptic, I'll remind you, because the victim makes a very determined and intelligently executed effort to conceal his memory lapse—frequently shutting himself up for several days on some pretext and feverishly studying all materials and documents relating to himself he can lay hands on. Undoubtedly sometimes he succeeds. The cases we hear about are those in which he makes such major slips—as being mistaken as to what his business is, who he is married to, who his friends are, what is going on in the world—that he is forced, against his will, to go to a psychiatrist. Whereupon, realizing that his efforts have failed, he generally confesses his amnesia, but is unable to offer any information as to its cause, or any convincing explanation of his attempt at concealment. Thereafter, readjustment is rapid."

He looked around. "And now, gentlemen, a matter which the experts didn't bring out, because I arranged it that way. I have saved it in order to impress it upon your minds as forcibly as possible—the correlation between cryptic amnesia and delusions of nonrecognition."

He paused with his hand near the box, aware that there was something of the conjurer about his movements and trying to minimize it. "I'm going to switch on both projections at once. Where cases of cryptic amnesia and delusions of nonrecognition coincide—I mean, where it is the cryptic amnesiac about whom the other person or persons had delusions of nonrecognition—the dots will likewise coincide; and you know what happens when violet and yellow light mix. I'll remind you that in ordinary cases of amnesia there are no delusions of nonrecognition—family and friends are aware of the victim's memory lapse, but they do not mistake him for a stranger."

His hand moved. Except for a sprinkling of yellow, the dots that glowed on the map were pure white.

"Complementary colors," said Clawly quietly. "The yellow has blanked out all the violet. In some cases one violet has accounted for a cluster of yellows—where more than one individual had delusions of nonrecognition about the same cryptic amnesiac. Except for the surplus cases of nonrecognition—which almost certainly correspond to cases of successfully concealed cryptic amnesia—the nonrecognitions and cryptic amnesias are shown to be dual manifestations of a single underlying phenomenon."

He paused. The tension in the Sky Room deepened. He leaned forward. "It is that underlying phenomenon, gentlemen, which I believe constitutes a threat to the security of the world, and demands the most immediate and thorough-going investigation. Though staggering, the implications are obvious."

The tautness continued, but slowly Conjerly got to his feet. His compact, stubby frame, bald bullet-head, and uncompromisingly impassive features were in striking contrast with Clawly's mobile, half-haggard, debonair visage.

Leashed anger deepened Conjerly's voice, enhanced its authority.

"We have come a long way from the Dawn Era, gentlemen. One might think we would never again have to grapple with civilization's old enemy superstition. But I am forced to that regretful conclusion when I hear this gentleman, to whom we have granted the privilege of an audience, advancing theories of demoniac possession to explain cases of amnesia and nonrecognition." He looked at Clawly. "Unless I wholly misunderstood?"

Clawly decisively shook his head. "You didn't. It is my contention—I might as well put it in plain words—that alien minds are displacing the minds of our citizens, that they are infiltering Earth, seeking to gain a foothold here. As to what minds they are, where they come from—I can't answer that, except to remind you that Thorn's studies of dream landscapes hint at a world strangely like our own, though strangely distorted. But the secrecy of the invaders implies that their purpose is hostile—at best, suspect. And I need not remind you that, in this age of subtronic power, the presence of even a tiny hostile group could become a threat to Earth's very existence."

Slowly Conjerly clenched his stub fingers, unclenched them. When he spoke, it was as if he were reciting a creed.

"Materialism is our bedrock, gentlemen—the firm belief that every phenomenon must have a real existence and a real cause. It has made possible science technology, unbiased self-understanding. I am open-minded. I will go as far as any in granting a hearing to new theories. But when those theories are a revival of the oldest and most ignorant superstitions, when this gentleman seeks to frighten us with nightmares and tales of evil spirits stealing human bodies, when he asks us on this evidence to institute a gigantic witch-hunt, when he raises the old bogey of subtronic power breaking loose, when he brings in a colleague"—he glared at Thorn—"who takes seriously to the idea of surveying dream worlds with transit and theodolite—then I say, gentlemen, that if we yield to such suggestions, we might as well throw materialism overboard and, as for safeguarding the future of mankind, ask the advice of fortunetellers!"

At the last word Clawly started, recovered himself. He dared not look around to see if anyone had noticed.

The anger in Conjerly's voice strained at its leash, threatened to break it.

"I presume, sir, that your confidential investigators will go out with wolfsbane to test for werewolves, garlic to uncover vampires, and cross and holy water to exorcise demons!"

"They will go out with nothing but open minds," Clawly answered quietly.

Conjerly breathed deeply, his face reddened slightly, he squared himself for a fresh and more uncompromising assault. But just at that moment Tempelmar eased himself out of his chair. As if by accident, his elbow brushed Conjerly's.

"No need to quarrel," Tempelmar drawled pleasantly, "though our visitor's suggestions do sound rather peculiar to minds tempered to a realistic materialism. Nevertheless, it is our duty to safeguard the world from any real dangers, no matter how improbable or remote. So, considering the evidence, we must not pass lightly over our visitor's theory that alien minds are usurping those of Earth—at least not until there has been an opportunity to advance alternate theories."

"Alternate theories have been advanced, tested, and discarded," said Clawly sharply.

"Of course," Tempelmar agreed smilingly. "But in science that's a process that never quite ends, isn't it?"

He sat down, Conjerly following suit as if drawn. Clawly was irascibly conscious of having got the worst of the interchange—and the lanky, sleepy-eyed Tempelmar's quiet skepticism had been more damaging than Conjerly's blunt opposition, though both had told. He felt, emanating from the two of them, a weight of personal hostility that bothered and oppressed him. For a moment they seemed like utter strangers.

He was conscious of standing too much alone. In every face he could suddenly see skepticism. Shielding was the worst—his expression had become that of a man who suddenly sees through the tricks of a sleight-of-hand artist masquerading as a true magician. And Thorn, who should have been mentally at his side, lending him support, was sunk in some strange reverie.

He realized that even in his own mind there was a growing doubt of the things he was saying.

Then, utterly unexpectedly, adding immeasurably to his dismay, Thorn got up, and without even a muttered excuse to the men beside him, left the room. He moved a little stiffly, like a sleepwalker. Several glanced after him curiously. Conjerly nodded. Tempelmar smiled.

Clawly noted it. He rallied himself. He said, "Well, gentlemen?"

Like a dreamer who falls head-foremost for giddy miles and then is wafted to a stop as gently as a leaf, Thorn plunged down the main vertical levitator of the Opal Cross and swam out of it at ground level, before its descent into the half mile of basements. At this hour the great gravity-less tube was relatively empty, except for the ceaseless silent plunge and ascent of the graduated subtronic currents and the air they swept along. There were a few other down-and-up swimmers—distant leaflike swirls of color afloat in the contracting white perspective of the tube—but, like a dreamer, Thorn did not seem to take note of them.

Another levitating current carried him along some hundred yards of mural-faced corridor to one of the pedestrian entrances of the Opal Cross. A group of revelers stopped their crazy, squealing dance in the current to watch him. They looked like figures swum out of the potently realistic murals—but with a more hectic, troubled gaiety on their faces. There was something about the way he plunged past them unseeing, his sleepwalker's eyes fixed on something a dozen yards ahead, that awakened unpleasant personal thoughts and spoiled their feverish fun-making.

The pedestrian entrance was really a city-limits. Here the one-building metropolis ended, and there began the horizontal miles of half-wild countryside, dark as the ancient past, trackless and roadless in the main, dotted in many areas with small private dwellings, but liberally brushed with forests.

A pair of lovers on the terrace, pausing for a kiss as they adjusted their flying togs, broke off to look curiously after Thorn as he hurried down the ramp and across the close-cropped lawn, following one of the palely-glowing pathways. The up-slanting pathlight, throwing into gaunt relief his angular cheek-bones and chin, made him resemble some ancient pilgrim or crusader in the grip of a religious compulsion.

Then the forest had swallowed him up.

A strange mixture of trance and willfullness, of dream and waking, of aimless wandering and purposeful tramping, gripped Thorn as he adventured down that black-fringed ghost-trail. Odd memories of childhood, of old hopes and desires, of student days with Clawly, of his work and the bewildering speculations it had led to, drifted across his mind, poignant but meaningless. Among these, but drained of significance, like the background of a dream, there was a lingering picture of the scene he had left behind him in the Sky Room. He was conscious of somehow having deserted a friend, abandoned a world, betrayed a great purpose—but it was a blurred consciousness and he had forgotten what the great purpose was.

Nothing seemed to matter any longer but the impulse pulling him forward, the sense of an unknown but definite destination.

He had the feeling that if he looked long enough at that receding, beckoning point a dozen yards ahead, something would grow there.

The forest path was narrow and twisting. Its faint glow silhouetted weeds and brambles partly over-growing it. His hands pushed aside encroaching twigs.

He felt something tugging at his mind from ahead, as if there were other avenues leading to his subconscious than that which went through his consciousness. As if his subconscious were the core of two or more minds, of which his was the only one.

Under the influence of that tugging, imagination awoke.

Instantly it began to recreate the world of his nightmares. The world which had obscurely dominated his life and turned him to dream-research, where he had found similar nightmares. The world where danger lay. The blue-litten world in which a mushroom growth of ugly squat buildings, like the factories and tenements and barracks of ancient times, blotched the utopian countryside, and along whose sluice-like avenues great crowds of people ceaselessly drifted, unhappy but unable to rest—among them that other, dream Thorn, who hated and envied him, deluged him with an almost unbearable sense of guilt.

For almost as long as he could remember, that dream Thorn had tainted his life—the specter at his feasts, the suppliant at his gates, the eternal accuser in the courts of inmost thought—drifting phantom-wise across his days, rising up starkly real and terrible in his nights. During the long, busy holiday of youth, when every day had been a new adventure and every thought a revelation, that dream Thorn had been painfully discovering the meaning of oppression and fear, had been security swept away and parents exiled, had attended schools in which knowledge was forbidden and all a man learned was his place. When he was discovering happiness and love, that dream Thorn had been rebelliously grieving for a young wife snatched away from him forever because of some autocratic government's arbitrary decrees. And while he was accomplishing his life's work, building new knowledge stone by stone, that dream Thorn had toiled monotonously at meaningless jobs, slunk away to brood and plot with others of his kind, been harried by a fiendishly efficient secret police, become a hater and a killer.

Day by day, month by month, year by year, the dark-stranded dream life had paralleled his own.

He knew the other Thorn's emotions almost better than his own, but the actual conditions and specific details of the dream Thorn's life were blurred and confused in a characteristically dreamlike fashion. It was as if he were dreaming that other Thorn's dreams—while, by some devilish exchange, that other Thorn dreamed his dreams and hated him for his good fortune.

A sense of guilt toward his dream-twin was the dominant fact in Thorn's inner life.

And now, pushing through the forest, he began to fancy that he could see something at the receding focus of his vision a dozen yards ahead, something that kept flickering and fading, so that he could scarcely be sure that he saw it, and that yet seemed an embodiment of all the unseen forces dragging him along—a pale, wraithlike face, horribly like his own.

The sense of a destination grew stronger and more urgent. The mile wall of the Opal Cross, a pale cataract of stone glimpsed now and then through overhanging branches, still seemed to rise almost at his heels, creating the maddening illusion that he was making no progress. The wraith-face blacked out. He began to run.

Twigs lashed him. A root caught at his foot. He stumbled, checked himself, and went on more slowly, relieved to find that he could at least govern the rate of his progress.

The forces tugging at him were both like and infinitely unlike those which had for a moment controlled his movements at the symchromy. Whereas those had seemed to have a wholly alien source, these seemed to have come from a single human mind.

He felt in his pocket for the object he had stolen from Clawly's mysterious confidant. He could not see much of its color now, but that made its baffling texture stand out. It seemed to have a little more inertia than its weight would account for. He was certain he had never touched anything quite like it before.

He couldn't say where the notion came from, but he suddenly found himself wondering if the thing could be a single molecule. Fantastic! And yet, was there anything to absolutely prevent atoms from assembling, or being assembled, in such a giant structure?

Such a molecule would have more atoms than the universe had suns.

Oversize molecules were the keys of life—the hormones, the activators, the carriers of heredity. What doors might not a supergiant molecule unlock?

The merest fancy—yet frightening. He started to throw the thing away, but instead tucked it back in his pocket.

There was a rush in the leaves. A large cat paused for an instant in the pathlight to snarl and stare at him. Such cats were common pets, for centuries bred for intelligence and for centuries tame. Yet now, on the prowl, it seemed all wild—with an added, evil insight gained from long association with man.

The path branched. He took a sharp turn, picking his way over bulbous roots. The pathlight grew dim and diffuse, its substance dissolved and spread by erosion. At places the vegetation had absorbed some of the luminescence. Leaves and stems glowed faintly.

But beyond, on either side, the forest was a black, choked infinity.

It had come inscrutably alive.

The sense of a thousand infinities pressing upon him, experienced briefly at the Yggdrasil, now returned with redoubled force.

The Yggdrasil was true. Reality was not what it seemed on the surface. It had many roots, some strong and true, some twisted and gnarled, nourished in many worlds.

He quickened his pace. Again something seemed to be growing at the focus of his vision—a flitting, pulsating, bluish glow. It was like the Yggdrasil's Nidhogg motif. Nidhogg, the worm gnawing ceaselessly at the root of the tree of life that goes down to hell. It droned against his vision—an unshakable color-tune.

Then, gradually, it became a face. His own face, but seared by unfamiliar emotions, haggard with unknown miseries, hard, vengeful, accusing—the face of the dream Thorn, beckoning, commanding, luring him toward some unknown destination in the maze of unknown, unseen worlds.

With a sob of courage and fear, he plunged toward it.

He must come to grips with that other Thorn, settle accounts with him, even the balance of pleasure and pain between them, right the wrong of their unequal lives. For in some sense he must be that other Thorn, and that other Thorn must be he. And a man could not be untrue to himself.

The wraithlike face receded as swiftly as he advanced.

His progress through the forest became a nightmarish running of the gauntlet, through a double row of giant black trees that slashed him with their branches.

The face kept always a few yards ahead.

Fear came, but too late—he could not stop.

The dreamy veils that had been drawn across his thoughts and memories during the first stages of his flight from the Opal Cross, were torn away. He realized that what was happening to him was the same thing that had happened to hundreds of other individuals. He realized that an alien mind was displacing his own, that another invader and potential cryptic amnesiac was gaining a foothold on Earth.

The thought hit him hard that he was deserting Clawly, leaving the whole world in the lurch.

But he was only a will-less thing that ran with outclutched hands.

Once he crossed a bare hilltop and for a moment caught a glimpse of the lonely glowing skylons—the Blue Lorraine, the Gray Twins, the Myrtle Y—but distant beyond reach, like a farewell.

He was near the end of his strength.

The sense of a destination grew overpoweringly strong.

Now it was something just around the next turn in the path.

He plunged through a giddy stretch of darkness thick as ink—and came to a desperate halt, digging in his heels, flailing his arms.

From somewhere, perhaps from deep within his own mind, came a faint echo of mocking laughter.

Like a mote in the grip of an intangible whirlwind, Clawly whipped through the gray dawn on a steady surge of subtronic power toward the upper levels of the Blue Lorraine. The brighter stars, and Mars, were winking out. Through the visor of his flying togs the rushing air sent a chill to which his blood could not quite respond. He should be home, recuperating from defeat, planning new lines of attack. He should be letting fatigue poisons drain normally from his plasma, instead of knocking them out with stimulol. He should be giving his thoughts a chance to unwind. Or he should have given way to lurking apprehensions and be making a frantic search for Thorn. But the itch of a larger worry was upon him, and until he had done a certain thing, he could not pursue personal interests, or rest.

With Thorn gone, his rebuff in the Sky Room loomed as a black and paralyzingly insurmountable obstacle that grew momently higher. They were lucky, he told himself, not to have had their present research funds curtailed—let alone having them increased, or being given a large staff of assistants, or being granted access to the closely guarded files of confidential information on cryptic amnesiacs and other citizens. Any earlier culture would probably have forbidden their research entirely, as a menace to the mental stability of the public. Only an almost fetishlike reverence for individual liberty and the inviolability of personal pursuits, had saved them.

The Committee's adverse decision had even shaken his own beliefs. He felt himself a puny little man, beset by uncertainties and doubts, quite incompetent to protect the world from dangers as shadowy, vast, and inscrutable as the gloom-drenched woodlands a mile below.

Why the devil had Thorn left the meeting like that, of necessity creating a bad impression? Surely he couldn't have given way to any luring hypnotic impulse—he of all men ought to know the danger of that. Still, there had been that unpleasant suggestion of sleepwalking in his departure—an impression that Clawly's memory kept magnifying. And Thorn was a strange fellow. After all these years, Clawly still found him unpredictable. Thorn had a spiritual recklessness, an urge to plumb all mental deeps. And God knows there were deeps enough for plumbing these days, if one were foolish. Clawly felt them in himself—the faint touch of a darker, less pleasant version of his own personality, against which he must keep constantly on guard.

If he had let something happen to Thorn—!

A variation in the terrestrial magnetic field, not responded to soon enough, sent him spinning sideways a dozen yards, forced his attention back on his trip.

He wondered if he had managed to slip away as unobtrusively as he had thought. A few of the committee members had wanted to talk. Firemoor, who had voted against the others and supported Clawly's views rather too excitedly, had been particularly insistent. But he had managed to put them off. Still, what if he were followed? Surely Conjerly's reference to "fortunetellers" had been mere chance, although it had given him a nasty turn. But if Conjerly and Tempelmar should find out where he was going now—What a handle that would give them against him!

It would be wiser to drop the whole business, at least for a time.

No use. The vice of the thing—if vice it be—was in his blood. The Blue Lorraine drew him as a magnet flicks up a grain of iron.

A host of images fought for possession of his tired mind, as he plunged through thin streamers of paling cloud. Green dots on the World Map. The greens and blues of the Yggdrasil—and in what nightmare worlds had Hoderson found his inspiration? The blue-tinted sketches one of Thorn's dreamers had made of the world of his nightmares. A sallow image of Thorn's face altered and drawn by pain, such an image as might float into the mind of one who watches too long by a sickbed. The looks on the faces of Conjerly and Tempelmar—that fleeting impression of a hostile strangeness. The hint of a dark alien presence in the depths of his own mind.

The Blue Lorraine grew gigantic, loomed as a vast, shadow-girt cliff, its topmost pinnacles white with frost although the night below had been summery. There were already signs of a new day beginning. Here and there freighters clung like beetles to the wall, discharging or receiving cargo through unseen ports. Some distance below a stream of foodstuffs for the great dining halls, partly packaged, partly not, was coming in on a subtronic current. Off to one side an attendant shepherded a small swarm of arriving schoolchildren, although it was too early yet for the big crowds.

Clawly swooped to a landing stage, hovered for a moment like a bird, then dropped. In the ante-room he and another early arriver helped each other remove and check their flying togs.

He was breathing hard, there was a deafness and a ringing in his ears, he rubbed his chilled fingers. He should not have made such a steep and swift ascent. It would have been easier to land at a lower stage and come up by levitator. But this way was more satisfying to his impatience. And there was less chance of someone following him unseen.

A levitating current wafted him down a quarter mile of mainstem corridor to the district of the psychologists. From there he walked.

He looked around uneasily. Only now did real doubt hit him. What if Conjerly were right? What if he were merely dragging up ancient superstitions, foisting them on a group of overspecialized experts, Thorn included? What if the world-threat he had tried to sell to the World Executive Committee were just so much morbid nonsense, elaborately bastioned by a vast array of misinterpreted evidence? What if the darker, crueler, deviltry-loving side of his mind were more in control than he realized? He felt uncomfortably like a charlatan, a mountebank trying to pipe the whole world down a sinister side street, a chaos-loving jester seeking to perpetrate a vast and unpleasant hoax. It was all such a crazy business, with origins far more dubious than he had dared reveal even to Thorn, from whom he had no other secrets. Best back down now, at least quit stirring up any more dark currents.

But the other urge was irresistible. There were things he had to know, no matter the way of knowing.

Stealing himself, he paraphrased Conjerly. "If the evidence seems to point that way, if the safety of mankind seems to demand it, then I will throw materialism overboard and ask the advice of fortunetellers!"

He stopped. A door faced him. Abruptly it was a doorway. He went in, approached the desk and the motionless, black-robed figure behind it.

As always, there was in Oktav's face that overpowering suggestion of age—age far greater than could be accounted for by filmy white hair, sunken cheeks, skin tight-drawn and wrinkle-etched. Unwilled, Clawly's thoughts turned toward the Dawn Civilization with its knights in armor and aircraft winged like birds, its whispered tales of elixirs of eternal life—and toward that oddly long-lived superstition, rumor, hallucination, that men clad in the antique garments of the Late Middle Dawn Civilization occasionally appeared on Earth for brief periods at remote places.

Oktav's garb, at any rate, was just an ordinary houserobe. But in their wrinkle-meshed orbits, his eyes seemed to burn with the hopes and fears and sorrows of centuries. They took no note of Clawly as he edged into a chair.

"I see suspense and controversy," intoned the seer abruptly. "All night it has surged around you. It regards that matter whereof we spoke at the Yggdrasil. I see others doubting and you seeking to persuade them. I see two in particular in grim opposition to you, but I cannot see their minds or motives. I see you in the end losing your grip, partly because of a friend's seeming desertion, and going down in defeat."

Of course, thought Clawly, he could learn all this by fairly simple spying. Still, it impressed him, as it always had since he first chanced—But was it wholly chance?—to contact Oktav in the guise of an ordinary psychologist.

Not looking at the seer, with a shyness he showed toward no one else, Clawly asked, "What about the world's future? Do you see anything more there?"

There was a faint drumming in the seer's voice. "Only thickening dreams, more alien spirits stalking the world in human mask, doom overhanging, great claws readying to pounce—but whence or when I cannot tell, only that your recent effort to convince others of the danger has brought the danger closer."

Clawly shivered. Then he sat straighter. He was no longer shy. Docketing the question about Thorn that was pushing at his lips, he said, "Look, Oktav, I've got to know more. It's obvious that you're hiding things from me. If I map the best course I can from the hints you give me, and then you tell me that it is the wrong course, you tie my hands. For the good of mankind, you've got to describe the overhanging danger more definitely."

"And bring down upon us forces that will destroy us both?" The seer's eyes stabbed at him. "There are worlds within worlds, wheels within wheels. Already I have told you too much for our safety. Moreover, there are things I honestly do not know, things hidden even from the Great Experimenters—and my guesses might be worse than yours."

Taut with a sense of feverish unreality, Clawly's mind wandered. What was Oktav—what lay behind that ancient mask? Were all faces only masks? What lay behind Conjerly's and Tempelmar's? Thorn's? His own? Could your own mind be a mask, too, hiding things from your own consciousness? What was the world—this brief masquerade of inexplicable events, flaring up from the future to be instantly extinguished in the past?

"But then what am I to do, Oktav?" he heard his tired voice ask.

The seer replied, "I have told you before. Prepare your world for any eventuality. Arm it. Mobilize it. Do not let it wait supine for the hunter."

"But how can I, Oktav? My request for a mere program of investigation was balked. How can I ask the world to arm—for no reason?"

The seer paused. When he finally answered there drummed in his voice, stronger than ever, the bitter wisdom of centuries.

"Then you must give it a reason. Always governments have provided appropriate motives for action, when the real motives would be unpalatable to the many, or beyond their belief. You must extemporize a danger that fits the trend of their short-range thinking. Now let me see—Mars—"

There was a slight sound. The seer wheeled around with a serpentine rapidity, one skinny hand plunged in the breast of his robe. It fumbled wildly, agitating the black, weightless fabric, then came out empty. A look of extreme consternation contorted his features.

Clawly's eyes shifted with his to the inner doorway.

The figure stayed there peering at Oktav for only a moment. Then, with an impatient, peremptory flirt of its head, it turned and moved out of sight. But it was indelibly etched, down to the very last detail, on Clawly's panic-shaken vision.

Most immediately frightening was the impression of age—age greater than Oktav's, although, or perhaps because, the man's physical appearance was that of thirty-odd, with dark hair, low forehead, vigorous jaw. But in the eyes, in the general expression—centuries of knowledge. Yet knowledge without wisdom, or with only a narrow-minded, puritanic, unsympathetic, overweening simulacrum of wisdom. A disturbing blend of unconscious ignorance and consciousness of power. The animal man turned god, without transfiguration.

But the most lingering impression, oddly repellent, was of its clothing. Crampingly unwieldly upper and nether garments of tight-woven, compressed, tortured animal-hair, fastened by bits of bone or horn. The upper garment had an underduplicate of some sort of bleached vegetable fiber, confined at the throat by two devices—one a tightly knotted scarf of crudely woven and colored insect spinnings, the other a high and unyielding white neckband, either of the same fiber as the shirt, glazed and stiffened, or some primitive plastic.

It gave Clawly an added, anti-climactic start to realize that the clothing of the nineteenth and twentieth centuries, which he had seen pictured in history albums, would have just this appearance, if actually prepared according to the ancient processes and worn by a human being.

Without explanation, Oktav rose and moved toward the inner doorway. His hand fumbled again in his robe, but it was merely an idle repetition of the earlier gesture. In the last glimpse he had of his face, Clawly saw continued consternation, frantic memory-searching, and the frozen intentness of a competent mind scanning every possible avenue of escape from a deadly trap.

Oktav went through the doorway.

There was no sound.

Clawly waited.

Time spun on. Clawly shifted his position, caught himself, coughed, waited, coughed again, got up, moved toward the inner doorway, came back and sat down.

There was time, too much time. Time to think again and again of that odd superstition about fleeting appearances of men in Dawn-Civilization garb. Time to make a thousand nightmarish deductions from the age in Oktav's, and that other's, eyes.

Finally he got up and walked to the inner doorway.

There was a tiny unfurnished room, without windows or another door, the typical secondary compartment of offices like this. Its walls were bare and seamless.

There was no one.

With a sickening ultimate plunge, that seemed to plumb in instants distances greater than the diameter of the cosmos—a plunge in which more than flesh and bones were stripped away, transformed—Oktav followed his summoner into a region of not only visual night.

Here in the Zone, outside the bubble of space-time, on the borders of eternity, even the atoms were still. Only thought moved—but thought powered beyond description or belief, thought that could make or mar universes, thought not unbefitting gods.

Most strange, then, to realize that it was human thought, with all its homely biases and foibles. Like finding, on another planet in another universe, a peasant's cottage with smoke wreathing above the thatched roof and an axe wedged in a half-chopped log.

Mice scurrying at midnight in a vast cathedral—and the faint suggestion that the cathedral might not be otherwise wholly empty.

Oktav, or that which had been Oktav, oriented itself—himself—making use of the sole means of perception that functioned in the Zone. It was most akin to touch, but touch strangely extended and sensitive only to projected thought or processes akin to thought.

Groping like a man shut in an infinite closet, Oktav felt the eternal hum of the Probability Engine, the lesser hum of the seven unlocked talismans. He felt the seven human minds in their stations around the engine, felt six of them stiffen with cold disapproval as Ters made report. Then he took his own station, the last and eighth.

Ters concluded.

Prim thought, "We summoned you, Oktav, to hear your explanation of certain highly questionable activities in which you have recently indulged—only to learn that you have additionally committed an act of unprecedented negligence. Never before has a talisman been lost. And only twice has it been necessary to make an expedition to recover one—when its possessor met accidental death in a space-time world. How can you have permitted this to happen, since a talisman gives infallible warning if it is in any way spatially or temporarily parted from its owner?"

"I am myself deeply puzzled," Oktav admitted. "Some obscure influence must have been operative, inhibiting the warning or closing my mind to it. I did not become aware of the loss until I was summoned. However, casting my mind back across the last Earth-day's events, I believe I can now discern the identity of the individual into whose hands it fell—or who stole it."

"Was the talisman inert at the time?" thought Prim quickly.

"Yes," thought Oktav. "A Key-idea known only to myself would be necessary to unlock its powers."

"That is one small point in your favor," thought Prim.

"I am gravely at fault," thought Oktav, "but it can easily be mended. Lend me another talisman and I will return to the world and recover it."

"It will not be permitted," thought Prim. "You have already spent too much time in the world, Oktav. Although you are the youngest of us, your body is senile."

Before he could check himself, or at least avoid projection, Oktav thought, "Yes, and by so doing I have learned much that you, in your snug retreat, would do well to become aware of."

"The world and its emotions have corrupted you," thought Prim. "And that brings me to the second and major point of our complaint."

Oktav felt the seven minds converge hostilely upon him. Careful to mask his ideational processes, Oktav probed the others for possible sympathy or weakness. Lack of a talisman put him at a great disadvantage. His hopes fell.

Prim thought, "It has come to our attention that you have been telling secrets. Moved by some corrupt emotionality, and under the astounding primitive guise of fortunetelling, you have been disbursing forbidden knowledge—cloudily perhaps, but none the less unequivocally—to earthlings of the main-trunk world."

"I do not deny it," thought Oktav, crossing his Rubicon. "The main-trunk world needs to know more. It has been your spoiled brat. And as often happens to a spoiled brat, you now push it, unprepared and unaided, into a dubious future."

Prim's answering thought, amplified by his talisman, thundered in the measureless dark. " We are the best judges of what is good for the world. Our minds are dedicated far more selflessly than yours to the world's welfare, and we have chosen the only sound scientific method for insuring its continued and ultimate happiness. One of the unalterable conditions of that method is that no Earthling have the slightest concrete hint of our activities. Has your mind departed so far from scientific clarity—influenced perhaps by bodily decay due to injudicious exposure to space-time—that I must recount to you our purpose and our rules?"

The darkness pulsed. Oktav projected no answering thought. Prim continued, thinking in a careful step-by-step way, as if for a child.

"No scientific experiment is possible without controls—set-ups in which the conditions are unaltered, as a comparison, in order to gauge the exact effects of the alteration. There is, under natural conditions, only one world. Hence no experiments can be performed upon it. One can never test scientifically which form of social organization, government, and so forth, is best for it. But the creation of alternate worlds by the Probability Engine changes all that."

Prim's thought beat at Oktav.

"Can it be that the underlying logic of our procedure has somehow always escaped you? From our vantage point we observe the world as it rides into the cone of the future—a cone that always narrows towards the present, because in the remote future there are many major possibilities still realizable, in the near future only a relative few. We note the approach of crucial epochs, when the world must make some great choice, as between democracy and totalitarianism, managerialism and servicism, benevolent elitism and enforced equalism and so on. Then, carefully choosing the right moment and focussing the Probability Engine chiefly upon the minds of the world's leaders, we widen the cone of the future. Two or more major possibilities are then realized instead of just one. Time is bifurcated, or trifurcated. We have alternate worlds, at first containing many objects and people in common, but diverging more and more—bifurcating more and more completely—as the consequences of the alternate decisions make themselves felt."

"I criticize," thought Oktav, plunging into uncharted waters. "You are thinking in generalities. You are personifying the world, and forgetting that major possibilities are merely an accumulation of minor ones. I do not believe that the distinction between the two major alternate possibilities in a bifurcation is at all clear-cut."

The idea was too novel to make any immediate impression, except that Oktav's mind was indeed being hazy and disordered. As if Oktav had not thought, Prim continued, "For example, we last split the time-stream thirty Earth-years ago. Discovery of subtronic power had provided the world with a practically unlimited source of space-time energy. The benevolent elite governing the world was faced with three clear-cut alternatives: It could suppress the discovery completely, killing its inventors. It could keep it a Party secret, make it a Party asset. It could impart it to the world at large, which would destroy the authority of the Party and be tantamount to dissolving it, since it would put into the hands of any person, or at least any small group of persons, the power to destroy the world. In a natural state, only one of these possibilities could be realized. Earth would only have one chance in three of guessing right. As we arranged it, all three possibilities were realized. A few years' continued observation sufficed to show us that the third alternative—that of making subtronic power common property—was the right one. The other two had already resulted in untold unendurable miseries and horrors."

"Yes, the botched worlds," Oktav interrupted bitterly. "How many of them have there been, Prim? How many, since the beginning?"

"In creating the best of all possible worlds, we of necessity also created the worst," Prim replied with a strained patience.

"Yes—worlds of horror that might have never been, had you not insisted on materializing all the possibilities, good and evil lurking in men's minds. If you had not interfered, man still might have achieved that best world—suppressing the evil possibilities."

"Do you suggest that we should leave all to chance?" Prim exploded angrily. "Become fatalists? We, who are masters of fate?"

"And then," Oktav continued, brushing aside the interruption, "having created those worst or near-worlds—but still human, living ones, with happiness as well as horror in them, populated by individuals honestly striving to make the best of bad guesses—you destroy them."

"Of course!" Prim thought back in righteous indignation. "As soon as we were sure they were the less desirable alternatives, we put them out of their misery."

"Yes." Oktav's bitterness was like an acid drench. "Drowning the unwanted kittens. While you lavish affection on one, putting the rest in the sack."

"It was the most merciful thing to do," Prim retorted. "There was no pain—only instantaneous obliteration."

Oktav reacted. All his earlier doubts and flashes of rebellion were suddenly consolidated into a burning desire to shake the complacency of the others. He gave his ironic thoughts their head, sent them whipping through the dark.

"Who are you to tell whether or not there's pain in instantaneous obliteration? Oh yes, the botched worlds, the controls, the experiments that failed—they don't matter, let's put them out of their misery, let's get rid of the evidence of our mistakes, let's obliterate them because we can't stand their mute accusations. As if the Earthlings of the botched worlds didn't have as much right to their future, no matter how sorry and troubled, as the Earthlings of the main trunk. What crime have they committed save that of guessing wrong, when, by your admission, all was guess-work? What difference is there between the main trunk and the lopped branches, except your judgment that the former seems happier, more successful? Let me tell you something. You've coddled the main-trunk world for so long, you've tied your limited human affections to it so tightly, that you've gotten to believing that it's the only real world, the only world that counts—that the others are merely ghosts, object lessons, hypothetics. But in actuality they're just as throbbingly alive, just as deserving of consideration, just as real."

"They no longer exist," thought Prim crushingly. "It is obvious that your mind, tainted by Earth-bound emotions, has become hopelessly disordered. You are pleading the cause of that which no longer is."

"Are you so sure?" Oktav could feel his questioning thought hang in the dark, like a great black bubble, coercing attention. "What if the botched worlds still live? What if, in thinking to obliterate them, you have merely put them beyond the reach of your observation, cut them loose from the main-trunk time-stream, set them adrift in the oceans of eternity? I've told you that you ought to visit the world more often in the flesh. You'd find out that your beloved main-trunkers are becoming conscious of a shadowy, overhanging danger, that they're uncovering evidences of an infiltration, a silent and mystery-shrouded invasion across mental boundaries. Here and there in your main-trunk world, minds are being displaced by minds from somewhere else. What if that invasion comes from one of the botched worlds—say from one of the worlds of the last trifurcation? That split occurred so recently that the alternate worlds would still contain many duplicate individuals, and between duplicate individuals there may be subtle bonds that reach even across the intertime void—on your admission, time-splits are never at first complete, and there may be unchanging shared deeps in the subconscious minds of duplicate individuals, opening the way for forced interchanges of consciousness. What if the botched worlds have continued to develop in the everlasting dark, outside the range of your knowledge, spawning who knows what abnormalities and horrors, like mutant monsters confined in caves? What if, with a tortured genius resulting from their misery, they've discovered things about time that even you do not know? What if they're out there—waiting, watching, devoured by resentment, preparing to leap upon your pet?"

Oktav paused and probed the darkness. Faint, but unmistakable, came the pulse of fear. He had shaken their complacency all right—but not to his advantage.

"You're thinking nonsense," Prim thundered at him coldly, in thought-tones in which there was no longer any hope of mercy or reprieve. "It is laughable even to consider that we could be guilty of such a glaring error as you suggest. We know every crevice of space-time, every twig and leaflet. We are the masters of the Probability Engine."

"Are you?" Reckless now of all consequences, Oktav asked the unprecedented, forbidden, ultimate question. "I know when I was initiated, and presumably when the rest of you were initiated, it was always assumed and strongly suggested, though never stated with absolute definiteness, that Prim, the first of us, a mental mutant and supergenius of the nineteenth century, invented the Probability Engine. I, an awestruck neophyte, accepted this attitude. But now I know that I never really believed it. No human mind could ever have conceived the Probability Engine. Prim did not invent it. He merely found it, probably by chancing on a lost talisman. Thereafter some peculiarity of the Engine permitted him to take it out of reach of its true owners, hide it from them. Then he took us in with him, one by one, because a single mind was insufficient to operate the Engine in all its phases and potentialities. But Prim never invented it. He stole it."

With a sense of exultation, Oktav realized that he had touched their primal vulnerability—though at the same time insuring his own doom. He felt the seven resentful, frightened minds converge upon him suffocatingly. He probed now for one thing only—any relaxing of watchfulness, any faltering of awareness, on the part of any one of them. And as he probed, he kept choking out additional insults against the resistance.

"Is there any one of you, Prim included, who even understands the Probability Engine, let alone having the capacity to devise it?

"You prate of science, but do you understand even the science of modern Earthlings? Can any one of you outline to me the theoretic background of subtronic physics? Even your puppets have outstripped you. You're atavisms, relics of the Dawn Civilization, mental mummies, apes crept into a factory at night and monkeying with the machinery.

"You're sorcerer's apprentices—and what will happen when the sorcerer comes back? What if I should stop this eternal whispering and send a call winging clear and unhampered through eternity: 'Oh sorcerer, True Owners, here is your stolen Engine'?"

They pressed on him frantically, frightenedly, as if by sheer mental weight to prevent any such call being sent. He felt that he would go down under the pressure, cease to be. But at the same time his probing uncovered a certain muddiness in Kart's thinking, a certain wandering due to doubt and fear, and he clutched at it, desperately but subtly.

Prim finished reading sentence. "—and so Ters and Septem will escort Oktav back to the world, and when he is in the flesh, make disposition of him." He paused, continued. "Meanwhile, Sikst will make an expedition to recover the lost talisman, calling for aid if not immediately successful. At the same time, since the functioning of the Probability Engine is seriously hampered so long as there is an empty station, Sekond, Kart and Kant will visit the world in order to select a suitable successor for Oktav. I will remain here and—"

He was interrupted by a flurry of startled thought from Kart, which rose swiftly to a peak of dismay.

"My talisman! Oktav has stolen it! He is gone!"

Thorn teetered on the dark edge. His footgear made sudden grating noises against it as he fought for balance. He was vaguely conscious of shouts and of a needle of green light swinging down at him.

Unavailingly he wrenched the muscles of his calves, flailed the air with his arms.

Yet as he lurched over, as the edge receded upward—so slowly at first!—he became glad that he had fallen, for the down-chopping green needle made a red-hot splash of the place where he had been standing.

He plummeted, frantically squeezing the controls of flying togs he was not wearing.

There was time for a futile, spasmodic effort to get clear in his mind how, plunging through the forest, he should find himself on that dark edge.

Indistinct funnel-mouths shot past, so close he almost brushed them. Then he was into something tangly that impeded his fall—slowly at first, then swiftly, as pressures ahead were built up. His motion was sickeningly reversed. He was flung upward and to one side, and came down with a bone-shaking jolt.

He was knee-deep in the stuff that had broken his fall. It made a rustling, faintly skirring noise as he ploughed his way out of it.

He stumbled around what must have been a corner of the dark building from whose roof he had fallen. The shouts from above were shut off.

He dazedly headed for one of the bluish glows. It faintly outlined scrawny trees and rubbish-littered ground between him and it.

He was conscious of something strange about his body. Through the twinges and numbness caused by his fall, it obtruded itself—a feeling of pervasive ill-health and at the same time a sense of light, lean toughness of muscular fiber—both disturbingly unfamiliar.

He picked his way through the last of the rubbish and came out at the top of a terrace. The bluish glow was very strong now. It came from the nearest of a line of illuminators set on poles along a broad avenue at the foot of the terrace. A crowd of people were moving along the avenue, but a straggly hedge obscured his view.

He started down, then hesitated. The tangly stuff was still clinging to him. He automatically started to brush it off, and noted that it consisted of thin, springy spirals of plastic and metal—identical with the shavings from an old-style, presubtronic hyperlathe. Presumably a huge heap of the stuff had been vented from the funnel-mouths he had passed in his fall. Though it bewildered him to think how many hyperlathes must be in the dark building he was skirting, to produce so much scrap. Hyperlathes were obsolete, almost a curiosity. And to gather so many engines of any sort into one building was unthought of.

His mind was jarred off this problem by sight of his hands and clothing. They seemed strange—the former pallid, thin, heavy-jointed, almost clawlike.

Sharp but far away, as if viewed through a reducing glass, came memories of the evening's events. Clawly, the symchromy, the old man in black, the conference in the Sky Room, his plunge through the forest.

There was something clenched in his left hand—so tightly that the fingers opened with difficulty. It was the small gray sphere he had stolen at the Yggdrasil. He looked at it disturbedly. Surely, if he still had that thing with him, it meant that he couldn't have changed. And yet—

His mind filled with a formless but mounting foreboding.

Under the compulsion of that foreboding, he thrust the sphere into his pocket—a pocket that wasn't quite where it should be and that contained a metallic cylinder of unfamiliar feel. Then he ran down the terrace, pushed through the straggly hedge, and joined the crowd surging along the blue-litten avenue.

The foreboding became a tightening ball of fear, exploded into realization.

That other Thorn had changed places with him. He was wearing that other Thorn's clothing—drab, servile, workaday. He was inhabiting that other Thorn's body—his own but strangely altered and ill-cared-for, aquiver with unfamiliar tensions and emotions.

He was in the world of his nightmares.

He stood stock-still, staring, the crowd flowing around him, jostling him wearily.

His first reaction, after a giant buffet of amazement and awe that left him intoxicatedly weak, was one of deep-seated moral satisfaction. The balance had at last been righted. Now that other Thorn could enjoy the good fortunes of utopia, while he endured that other Thorn's lot. There was no longer the stifling sense of being dominated by another personality, to whom misfortune and suffering had given the whiphand.

He was filled with an almost demoniac exhilaration—a desire to explore and familiarize himself with this world which he had long studied through the slits of nightmare, to drag from the drifting crowd around him an explanation as to its whys and wherefores.

But that would not be so easy.

An atmosphere of weary secrecy and suspicion pervaded the avenue. The voices of the people who jostled him dropped to mumbles as they went by. Heads were bowed or averted—but eyes glanced sharply.

He let himself move forward with the crowd, meanwhile studying it closely.

The misery and boredom and thwarted yearning for escape bluely shadowed in almost all the faces, was so much like that he remembered from his nightmares that he could easily pretend that he was dreaming—but only pretend.

There was a distorted familiarity about some of the faces that provided undiminishing twinges of horror. Those must be individuals whose duplicates in his own world he vaguely knew, or had glimpsed under different circumstances.

It was as if the people of his own world were engaged in acting out some strange pageant—perhaps a symbolic presentation dedicated to all the drab, monotonous, futile lives swallowed up in the muck of history.

They were dressed, both men and women, in tunic and trousers of some pale color that the blue light made it impossible to determine. There was no individuality—their clothes were all alike, although some seemed more like work clothes, others more like military uniforms.

Some seemed to be keeping watch on the others. These were treated with a mingled deference and hostility—way was made for them, but they were not spoken to. And they were spied on in turn—indeed, Thorn got the impression of an almost intolerably complex web of spying and counterspying.

Even more deference was shown to occasional individuals in dark clothing, but for a time Thorn did not get a close glimpse of any of these.

Everyone seemed on guard, wearily apprehensive.

Everywhere was the suggestion of an elaborate hierarchy of authority.

There was a steady drone of whispered or mumbled conversation.

One thing became fairly certain to Thorn before long. These people were going nowhere. All their uneasy drifting had no purpose except to fill up an empty period between work and sleep—a period in which some unseen, higher authority allowed them freedom, but forbid them from doing anything with it.

As he drifted along Thorn became more a part of the current, took on its coloring, ceased to arouse special suspicion. He began to overhear words, phrases, then whole fragments of dialogue. All of these had one thing in common: some mention of, or allusion to, the activities of a certain "they." Whatever the subject-matter, this pronoun kept cropping up. It was given a score of different inflections, none of them free from haunting anxiety and veiled resentment. There grew in Thorn's mind the image of an authority that was at once tyrannical, fatherly, arbitrary, austere, possessed of overpowering prestige, yet so familiar that it was never referred to in any more definite way.

"They've put our department on a twelve-hour shift."

The speaker was evidently a machinist. Anyway, a few hyperlathe shavings stuck to his creased garments.

His companion nodded. "I wonder what the new parts that are coming through are for."

"Something big."

"Must be. I wonder what they're planning."

"Something big."

"I guess so. But I wish we at least knew the name of what we're building."

No answer, except a tired, mirthless chuckle.

The crowd changed formation. Thorn found himself trailing behind another group, this time mostly elderly women.

"Our work-group has turned out over seven hundred thousand identical parts since the speed-up started. I've kept count."

"That won't tell you anything."

"No, but they must be getting ready for something. Look at how many are being drafted. All the forty-one-year-olds, and the thirty-seven-year-old women."

"They came through twice tonight, looking for Recalcitrants. They took Jon."

"Have you had the new kind of inspection? They line you up and ask you a lot of questions about who you are and what you're doing. Very simple questions—but if you don't answer them right, they take you away."

"That wouldn't help them catch Recalcitrants. I wonder who they're trying to catch now."

"Let's go back to the dormitory."

"Not for a while yet."

Another meaningless shift put Thorn next to a group containing a girl.

She said, "I'm going into the army tomorrow."

"Yes."

"I wish there were something different we could do tonight."

"They won't let us do anything." A weak, whining note of rebellion entered her voice. "They have everything—powers like magic—they can fly—they live in the clouds, away from this horrible light. Oh, I wish—"

" Sh! They'll think you're a Recalcitrant. Besides, all this is temporary—they've told us so. There'll be happiness for everyone, as soon as the danger is over."

"I know—but why won't they tell us what the danger is?"

"There are military reasons. Sh! "

Someone who smiled maliciously had stolen up behind them, but Thorn did not learn the sequence to this interlude, if it had one, for yet another shift carried him to the other side of the avenue and put him near two individuals, a man and a woman, whose drab clothing was of the more soldierly cut.

"They say we may be going on maneuvers again next week. They've put a lot of new recruits in with us. There must be millions of us. I wish I knew what they were planning to do with us, when there's no enemy."

"Maybe things from another planet—"

"Yes, but that's just a rumor."

"Still, there's talk of marching orders coming any day now—complete mobilization."

"Yes, but against what?" The woman's voice had a faint overtone of hysteria. "That's what I keep asking myself at practice whenever I look through the slit and depress the trigger of the new gun—not knowing what it is that the gun will shoot or how it really works. I keep asking myself, over and over, what's going to be out there instead of the neat little target—what it is I'm going to kill. Until sometimes I think I'm going crazy. Oh Burk, there's something I've got to tell you, though I promised not to. I heard it yesterday—I mustn't tell who told me. It's that there's really a way of escape to that happier world we all dream of, if only you know how to concentrate your mind—"

" Sh! "

This time it was Thorn's eavesdropping that precipitated the warning.

He managed to listen in on many similar, smaller fragments of talk.

Gradually a change came over his mood—a complete change. His curiosity was not satisfied, but it was quenched. Oh, he had guessed several things from what he had heard, all right—in particular, that the "new kind of inspection" was designed to uncover displaced minds like his own, and that the "way of escape" was the one the other Thorn had taken—but this knowledge no longer lured him on. The fever of demoniac excitement had waned as swiftly as drunkenness, and left as sickening a depression in its wake. Normal human emotions were re-asserting themselves—a shrinking from the ominous strangeness of this distorted world, and an aching, unreasoning, mountingly frantic desire to get back to familiar faces and scenes.

Bitter regret began to torture him for having deserted Clawly and his home-world because of the pressure of a purely personal moral problem. No knowing what confusions and dangers the other Thorn might weave for an unsuspecting Clawly. And upon Clawly alone, now that he was gone, the safety of the home-world depended. True, if most of the displacing minds from this world were only those of oppressed individuals seeking escape, they would constitute no immediate unified danger. But if the shadowy, autocratic "they" were contemplating an invasion—that would be a very different matter.

The avenue, now skirting some sort of barren hillside, had become hateful to him. It was like a treadmill, and the glaring lights prevented any extended glimpse of the surrounding landscape. He would probably have left it soon in any case, even without sight of the jam-up ahead, where some sort of inspection of all walkers seemed to be going on. As it was, that sight decided him. He edged over to the side, waited for what he thought was a good opportunity, and ducked through the hedge.

Some minutes later, panting from concentrated exertion, his clothes muddied and grass-stained, he came out on the hilltop. The darkness and the familiar stars were a relief. He looked around.

His first impression was reassuring. For a moment it even roused in him the hope that, in his scramble up the hillside, the world had come right again. There, where it should be, was the Opal Cross. There were the Gray Twins. Concentrating on them, he could ignore the unpleasant suggestion of darker, squatter buildings bulging like slugs or beetles from the intervening countryside, could ignore even the meshwork of blue-litten, crawling avenues.

But the aerial bridge connecting the Twins must be darked out. Still, in that case the reflected light from the two towers ought to enable him to catch the outlines of either end of it.

And where was the Blue Lorraine? It didn't seem a hazy enough night to blot out that vast skylon.

Where, between him and the Twins, was the Mauve Z?

Shakingly he turned around. For a moment again his hope surged up. The countryside seemed clearer this way, and in the distance the Myrtle Y and the Gray H were like signposts of home.

But between him and them, rearing up from that very hillside where this evening he had watched the Yggdrasil, as if built in a night by jinn, was a great dark skylon, higher than any he had ever seen, higher even than the Blue Lorraine. It had an ebon shimmer. The main elements of its structure were five tapering wings radiating at equal intervals from a central tower. It looked like some symbol of pride and power conceived in the dreams of primeval kings.

A name came to him. The Black Star.

"Who are you up there? Come down!"

Thorn whirled around. The blue glare from the avenue silhouetted two men halfway up the hillside. Their heads were craned upward. The position of their arms suggested that they held weapons of some sort trained upon him.

He stood stock-still, conscious that the blue glow extended far enough to make him conspicuous. His senses were suddenly very keen. The present instant seemed to widen out infinitely, as if he and his two challengers were frozen men. It burst on him, with a dreadful certainty, that those men shouting on the roof had been trying to kill him. Save for the luck of overbalancing, he would this moment be a mangled cinder. The body he was in was one which other men were trying to kill.

"Come down at once!"

He threw himself flat. There was no needle of green, but something hissed faintly through the grass at his heels. He wriggled desperately for a few feet, then came up in a crouch and ran recklessly down the hillside away from the avenue.

Luck was with him. He kept footing in his crazy, breathless plunge through the semidark.

He entered thin forest, had to go more slowly. Leaves and fallen branches crackled under his feet. Straggly trees half blotted the stars.

All at once he became aware of shouting ahead. He turned, following a dry gravelly watercourse. But after a while there was shouting in that direction, too. Then something big swooped into the sky overhead and hung, and from it exploded blinding light, illumining the forest with a steady white glare crueler than day's.

He dove to cover in thick underbrush.

For a long time the hunt beat around him, now receding a little, now coming close. Once footsteps crunched in the gravel a dozen feet away.

The underbrush, shot through with the relentless white glare, seemed a most inadequate screen. But any attempt to change position would be very risky.

He hitched himself up a little to peer through the gaps in the leaves, and found that his right hand was clutching the metal cylinder he had felt in his pocket earlier. He must have snatched it out at some stage in his flight—perhaps an automatic response of his alien muscles.

He examined the thing, wondering if it were a weapon. He noted two controlling levers, but their function was unclear. As a last resort, he could try pointing the thing and pushing them.

A rustle of leaves snapped his attention to one of the leafy gaps. A figure had emerged on the opposite bank of the dried watercourse. It was turned away, but from the first there was something breathlessly familiar about the self-assured posture, the cock of the close-cropped, red-haired head.

The theatric glare struck an ebon shimmer from the uniform it was wearing, and outlined on one shoulder, of a somberer blackness than the uniform, a black star.

Thorn leaned forward, parting with his hand the brambly wall of his retreat.

The figure turned and the face became visible.

In a strangled voice—his first words since he had found himself on the roof-edge—Thorn cried out, "Clawly!" and rushed forward.

For a moment there was no change in Clawly's expression. Then, with feline agility, he sprang to one side. Thorn stumbled in the pitted streambed, dropped the metal cylinder. Clawly whipped out something and pointed it. Thorn started up toward him. Then—there was no sound save a faint hissing, no sight, but agonizing pain shot through Thorn's right shoulder.

And stayed. Lesser waves of it rippled through the rest of his body. He was grotesquely frozen in the act of scrambling upward. It was as if an invisible red-hot needle in Clawly's hand transfixed his shoulder and held him helpless.

Staring up in shocked, tortured dismay, the first glimmerings of the truth came to Thorn.

Clawly— this Clawly—smiled.

Clawly quit his nervous prowling and perched on Oktav's desk. His satanic face was set in tight, thwarted lines. Except for his rummaging everything in the room was just as it had been when he had stolen out early this morning. The outer door aslit, Oktav's black cloak thrown over the back of his chair, the door to the empty inner chamber open. As if the seer had been called away on some brief, minor errand.

Clawly was irked at the impulse which had drawn him back to this place. True, his rummaging had uncovered some suggestive and disquieting things—in particular, an assortment of small objects and implements that seemed to extend back without a break to the Late Middle Dawn Civilization, including a maddeningly random collection of notes that began in faded stain on sheets of bleached and compressed vegetable fiber, shifted to typed characters on similar sheets, kept on through engraving stylus and plastic film to memoranda ribbon and recording wire, and finally ended in multilevel writing tape.

But what Clawly wanted was something that would enable him to get a hook into the problem that hung before him like a vast, slippery, ungraspable sphere.

He still had, strong as ever, the conviction that this room was the center of a web, the key to the whole thing—but it was a key he did not know how to use.

His heels beat a muffled tattoo against the desk as he searched his mind for possible alternate avenues of attack.

Thorn? That was a whole problem in itself, only a few hours old, but full of the most nerve-racking possibilities. He took from his pouch and nervously fingered the fragment of tape with its scrawlingly recorded message which he had found earlier today on Thorn's desk at their office—that message which no one had seen Thorn leave.

Although the general style of recording was characteristically Thorn's, it had a subtly different swing to it, an alien undercurrent, as if some other mind were using Thorn's habitual patterns of muscular action. And the message itself, which might refer to anything, was alarmingly suggestive of a cryptic amnesiac's play for time.

On the other hand, it would be just like Thorn to play the lone wolf if he saw fit.

If he followed his simplest impulses, Clawly would resume the search for Thorn he had begun on finding the message. But he had already put that search into the hands of agencies more competent than any single individual could possibly be. They would find Thorn if anyone could, and for him to try to help them would merely be a concession to his anxiety.

His heels beat a sharper tattoo.

The research program? But that was crippled by the Committee's adverse decision, and by Thorn's absence. He couldn't do much there. Besides he had the feeling that any research program was becoming too slow and remote a measure for dealing with the present situation.

The Committee itself? But what single, definite thing could he tell them that he had not told them last night?

His own mind, then? How about that as an avenue of attack? Stronger than ever before, the conviction came that there were dark avenues leading down from his consciousness—one of them to a frighteningly devilish, chaos-loving version of himself—and that if he concentrated his mind in a certain peculiar way he might be able to slip down one of them.

There was a devil-may-care lure to those dark avenues—the promise of a world better suiting the darker, Dawn phases of his personality. And, if Thorn had been displaced, that would be the only way of getting to him.

But that wasn't grappling with the problem. That was letting go, plunging with indefensible recklessness into the unknown—a crazy last resort.

To grapple with a problem, you had to have firm footing—and grab.

The tattoo ended with a sudden slam of heels. Was this room getting on his nerves? This silent room, with its feel of tangible linkages with future and past, its sense of standing on the edge of a timeless, unchanging center of things, in which action had no place—sapping his will power, rendering him incapable of making a decision, now that there was no longer a seer to interpret for him.

The problem was in one sense so clear-cut. Earth threatened by invasion from across a new kind of frontier.

But to get a grip on that problem.

He leaned across the desk and flipped the televisor, riffling through various local scenes in the Blue Lorraine. The Great Rotunda, with its aerial promenade, where a slow subtronic current carried chatting, smiling throngs in an upward spiral past displays of arts and wares. The Floral Rotunda, where pedestrians strolled along gently rolling paths under arches of exotic greenery. The other formal social centers. The endless corridors of individual enterprises, where one might come upon anything from a puppet-carver's to a specialized subtronic lab, a mood-creator's to a cat-fancier's. The busy schools. The production areas, where keen-eyed machine tenders governed and artistically varied the flow of processing. The maintenance and replacement centers. The vast kitchens, where subtle cooks ruled to a hairbreadth the mixing of foodstuffs and their exposure to heat and moisture and other influences. The entertainment and games centers, where swirling gaiety and high-pitched excitement were the rule.

Everywhere happiness—or, rather, creative freedom. A great rich surging world, unaware, save for nightmare glimpses, of the abyss-edge on which it danced.

Maddeningly unaware.

Clawly's features writhed. Thus, he thought, the Dawn gods must have felt when looking down upon mankind the evening before Ragnarok.

To be able to shake those people out of their complacency, make them aware of danger!

The seer's words returned to him: "Arm it. Mobilize it. Do not let it wait supine for the hunter—You must give it a reason ... extemporize a danger—Mars."

Mars! The seer's disappearance had caused Clawly to miss the idea behind the word, but now, remembering, he grasped it in a flash. A faked Martian invasion. Doctored reports from the First Interplanetary Expedition—mysterious disappearance of spaceships—unknown craft approaching Earth—rumor of a vast fleet—running fights in the stratosphere—

Firemoor of the Extraterrestrial Service was his friend, and believed in his theories. Moreover, Firemoor was daring—even reckless. Many of the young men under him were of similar temperament. The thing could be done!

Abruptly Clawly shook his head, scowled. Any such invasion scare would be a criminal hoax. It was a notion that must have been forced upon him by the darker, more wantonly mischievous side of his nature—or by some lingering hypnotic influence of Oktav.

And yet—

No! He must forget the notion. Find another way.

He slid from the desk, began to pace. Opposition. That was what he needed. Something concrete to fight against. Something, some person, some group, that was opposed to him, that was trying to thwart him at every turn.

He stopped, wondering why he had not thought of it before.

There were two men who were trying to thwart him, who had shrewdly undermined his and Thorn's theories, two men who had shown an odd personality reversal in the past months, who had impressed him with a fleeting sense of strangeness and alienage.

Two members of the World Executive Committee.

Conjerly and Tempelmar.

Brushing the treetops, swooping through leaf-framed gaps, startling a squirrel that had been dozing on an upper branch, Clawly glided into the open and made a running landing on the olive-floored sun-deck of Conjerly's home.

It was very quiet. There was only the humming of some bees in the flower garden, up from which sweet, heavy odors drifted sluggishly and curled across the deck. The sun beat down. On all sides without a break, the trees—solid masses of burnished leaves—pressed in.

Clawly crossed quietly to the dilated doorway in the cream-colored wall. He did not remove his flying togs. His visor he had thrown open during flight.

Raising his hand, he twice broke the invisible beam spanning the doorway. A low musical drone sounded, was repeated.

There was no answering sound, no footsteps. Clawly waited.

The general quiet, the feeling of lifelessness, made his abused nerves twitch. Forest homes like this, reached only by flying, were devilishly lonely and isolated.

Then he became aware of another faint, rhythmic sound, which the humming of the bees had masked. It came from inside the house. Throaty breathing. The intervals between breaths seemed abnormally long.

Clawly hesitated. Then he smoothly ducked under the beam.

He walked softly down a dark, cool corridor. The breathing grew steadily louder, though there was no change in its labored, sighing monotony. Opposite the third opened doorway the increase in volume was abrupt.

As his eyes became accustomed to the semidarkness, he made out a low couch and the figure of a man sprawled on it, on his back, arms dropped to either side, pale blob of bald head thrown limply back. At intervals the vague face quivered with the slow-paced breathing.

Clawly fumbled sideways, switched on a window, went over to the couch.

On the floor, under Conjerly's hand, was a deflated elastoid bag. Clawly picked it up, sniffed, quickly averted his head from the faintly pungent soporific odor.

He shook the bulky sleeper, less gently after a moment.

It did not interrupt the measured snores.

The first impression of Conjerly's face was one of utter emptiness, the deep-grooved wrinkles of character and emotion a network of disused roads. But on closer examination, hints of personality became dimly apparent, as if glimpsed at the bottom of a smudgy pool.

The longer Clawly studied them, the surer he became that the suspicions he had clutched at so eagerly in Oktav's office were groundless. This was the Conjerly he had known. Unimaginative perhaps, stubborn and blunt, a little too inclined to conservatism, a little too fond of curling down those deep furrows at the corners of the mouth—but nothing alien, nothing malign.

The rhythm of the breathing changed. The sleeper stirred. One hand came slowly up, brushed blindly at the chest.

Clawly watched motionlessly. From all sides the heavy summery silence pressed in.

The rhythm of the breathing continued to change. The sleeper tossed. The hand fumbled restlessly at the neck of the loose house robe.

And something else changed. It seemed to Clawly as if the face of the Conjerly he knew were sinking downward into a narrow bottomless pit, becoming tiny as a cameo, vanishing utterly, leaving only a hollow mask. And then, as if another face were rising to fill the mask—and in this second face, if not malignity, at least grim and unswervingly hostile purpose.

The sleeper mumbled, murmured. Clawly bent low, caught words. Words with a shuddery, unplacable quality of distance to them, as if they came from another cosmos.

"... transtime machine ... invasion ... three days ... we ... prevent action ... until—"

Then, from the silence behind him, a different sound—a faint crunch.

Clawly whirled. Standing in the doorway, filling half its width and all its height, was Tempelmar.

And in Tempelmar's lean, horse-like face the vanishing flicker of a look in which suspicion, alarm, and a more active emotion were blended—a lethal look.

But by the time Clawly was looking straight at him, it had been replaced by an urbane, condescending, eyebrow-raising "Well?"

Again a sound from behind. Turning, backing a little so that he could take in both men at once, Clawly saw that Conjerly was sitting up, rubbing his face. He took away his hands and his small eyes stared at Clawly—blankly at first. Then his expression changed too, became a "Well?"—though more angry, indignant, less urbane. It was an expression that did not belong to the man who had lain there drugged.

The words Clawly had barely caught were still humming in his ears.

Even as he phrased his excuse—"... came to talk with you about the program ... heard sounds of distressed breathing ... alarmed ... walked in ..."—even as he considered the possibility of immediate physical attack and the best way to meet it, he came to a decision.

He would see Firemoor.

With bent shoulders, sunken head, paralyzed arm still dangling at his side, Thorn crouched uncomfortably in his lightless cell, as if the whole actual weight of the Black Star—up to the cold, cloud-piercing pinnacle where "they" held council—were upon him. His mind was tired to the breaking point, oppressed by the twisted, tyrannous world into which he had blundered, by the aching body not his own, by the brain which refused to think his thoughts in the way he wanted to think them.

And yet, in a sense, the human mind is tireless—an instrument built for weary decades of uninterrupted thinking and dreaming. And so Thorn continued to work on, revolving miseries, regrets, and fears, striving to unlock the stubborn memory chambers of the unfamiliar brain, turning from that to equally hopeless efforts to make plans. Mostly it struggled nightmarishly with the problem of escape back to his own world, and with the paradoxical riddles which that problem involved. He must, Thorn told himself, still be making partial use of his brain back in World I—to give it a name—just as Thorn II—to give him a name—must be making use of these locked memory chambers. All thought had to be based on a physical brain; it couldn't go on in emptiness. Also, since Universes I and II—to give them names—were independent, self-contained space-time set-ups, they couldn't have an ordinary spatial relationship—they couldn't be far from or near to each other. The only linkage between them seemed to be the mental ones between quasi-duplicate brains, and such linkages would not involve distance in any common sense of the term. His transition into World II had seemed to take place instantaneously; hence, pragmatically speaking, the two universes could be considered as super-imposed on each other. Whether he was in one or the other was just a matter of viewpoint.

So near and yet so far. So diabolically similar to attempts to wake from a nightmare—and the blackness of his cell increased the similarity. All he had to do was summon up enough mental energy, find sufficient impetus, to force a re-exchange of viewpoints between himself and Thorn II. And yet as he struggled and strained through seeming eternities in the dark, as he strove to sink, to plunge, down the dark channels of the subconscious and found them closed, as he felt out the iron resistances of that other Thorn, he began to think the effort impossible—even began to wonder if World I were not just the wishful dream of a scarred, hunted, memoryless man in a world where invisible tyrants plotted un-understandable invasions, commanded the building of inexplicable machines, and bent millions to their wholly cryptic will.

At least, whatever the sufficient impetus was, he could not find it.

A vertical slit of light appeared, widened to a square, revealed a long corridor. And in it, flanked by two black-uniformed guards, the other Clawly.

So similar was the dapper figure to the Clawly he knew—rigged out in a strange costume and acting in a play—that it was all he could do not to spring up with a friendly greeting.

And then, to think that this Clawly's mind was linked to the other's, that somewhere, just across its subconscious, his friend's thoughts moved—Dizzying. He stared at the trim, ironic face with a terrible fascination.

Clawly II spoke. "Consider yourself flattered. I'm going to deliver you personally to the Servants of the People. They'll want to be the ones to decide, in your case, between immediate self-sacrifice, assisted confession, or what not." He chuckled without personal malice. "The Servants have devised quite amusing euphemisms for Death and Torture, haven't they? The odd thing is, they seem to take them seriously—the euphemisms, I mean."

The uniformed guards, in whose stolid faces were written years of unquestioning obedience to incomprehensible orders, did not laugh. If anything, they looked shocked.

Thorn staggered up and stepped slowly forward, feeling that by that action he was accepting a destiny not of his own making but as inescapable as all destinies are, that he was making his entrance, on an unknown stage, into an unknown play. They started down the corridor, the guards bringing up the rear.

"You make rather a poorer assassin than I'd have imagined, if you'll pardon the criticism," Clawly II remarked after a moment. "That screaming my name to get me off guard—a very ill-advised dodge. And then dropping your weapon in the streambed. No—you can't exactly call it competent. I'm afraid you didn't live up to your reputation of being the most dangerous of the Recalcitrants. But then, of course, you were fagged."

Thorn sensed something more in the remarks than courteous knife-twisting. Undeniably, Clawly II was vaguely aware of something off-key, and was probing for it. Thorn tightened his guard, for he had decided on at least one thing in the dark—that he would not reveal that he was a displaced mind, except to escape some immediate doom. It might be all right if they would consider him insane. But he was reasonably certain they would not.

Clawly II looked up at him curiously. "Rather silent, aren't you? Last time we met, as I recall, you denounced me—or was it the things I stood for?—in the most bitter language, though with admirable restraint. Can it be that you're beginning to reconsider the wisdom of recalcitrance? Rather late for that, I'm afraid."

He waited a while. Then, "It's you that hates me, you know. I hate no one." He caught Thorn's involuntary grimace, the twitch of the shoulder from which hung the paralyzed right arm. "Oh, I sometimes hurt people, but that's mainly adjustment to circumstances—quite another thing. My ideal, which I've pretty well achieved, is to become so perfectly adjusted to circumstances that I float freely on the stream of life, unannoyed by any tugs of hate, love, fear, caution, guilt, responsibility, and so forth—all the while enjoying the spectacle and occasionally poking in a finger."

Thorn winced—Clawly II's remarks were so similar to those which Clawly I sometimes made when he was in a banteringly bitter mood. Certainly the man must have some sort of suspicions and be trying to draw him out—he'd never talk so revealingly otherwise. Beyond that, there was the suggestion that Clawly II was bothered by certain unaccustomed feelings of sympathy and was trying to get to the bottom of them. Perhaps the independence of quasi-duplicate minds wasn't as complete as it had at first appeared. Perhaps Clawly I's emotions were obscurely filtering through to Clawly II. It was all very confusing, unnervingly so, and Thorn was relieved when their entry into a large room postponed the moment when he would have to decide on a line of answers.

It was an arresting room, chiefly because it was divided into two areas in which two separate ways of life held sway, as clearly as if there had been a broad white line extending across the middle, with the notice, "Thou shalt not pass." On this side was quite a crowd of people, most of them sitting around on benches, a few in black uniforms, the rest in servile gray. They were all obviously waiting—for orders, permissions, judgments, interviews. They displayed, to an exaggerated degree, that mixture of uneasiness and boredom characteristic of people who must wait. Four words sprang to Thorn's mind, summing them up. They did not know.

On the other side were fewer people—a bare half dozen, seated at various desks. Their superiority was not obviously displayed. Their clothing was, if anything, drabber and more severe, and the furnishings they used were in no way luxurious. But something in their manner, something in the way they glanced speculatively up from their work, put gulfs between them and those who uneasily waited. This time only two words were needed. They knew.

Clawly II's arrival seemed to cause an increase in the uneasiness. At least, Thorn caught several frightened glances, and sensed a general relaxing of tension when it became obvious that Clawly II's mission did not concern anyone here. He also noted that the two guards seemed relieved when Clawly dismissed them.

One other glance he thought he caught was of a perplexingly different sort. It was directed at him rather than Clawly II. It came from an elderly, gray-clad man, whose face awoke no sense of recognition either in this world or his own. It conveyed, if he was not mistaken, sympathy, anxiety, and—strangest of all— loyalty . Still, if Thorn II had been some sort of rebel leader, the incident was understandable. Thorn quailed, wondering if he had put himself into the position of betraying a worthy movement in this world as well as his own.

Clawly II seemed to be a person of reputation on the other side of the room as well, for his clipped, "To the Servants' Hall, with a person for the Servants," passed them through without a question.

They entered another corridor, and their surroundings began to change very rapidly. A few paces brought them to a subtronic tube. Thorn was glad that he was startled into moving jerkily when the upward-surging current gripped them, for a glance at Clawly II warned him that it would not be well to show much familiarity with this form of transportation.

And now, for the first time since his plunge into World II, Thorn's mind began to work with clarity. It may have been the soothing familiarity of the current.

Obviously, in World II subtronic power was the closely-guarded possession of a ruling elite. There had been no evidence at all of its employment on the other side of the dividing line. Moreover, that would explain why the workers and soldiers on the other side were kept ignorant of the true nature and theory of at least some of the instruments they constructed or used. It would also explain the need for the vast amount of work—there were two ways of life, based on entirely different power-systems, to be maintained.

Then as to the relationship between Worlds I and II. For closely related they must be—it was unthinkable that two eternally independent universes could have produced two near-identical Opal Crosses, Gray Twins, Clawlys, Thorn, and an uncounted host of other similars; if one granted that possibility, one would have to grant anything. No—Worlds I and II must be the results of a split in the time-stream, however caused, and a fairly recent split at that, for the two worlds contained duplicate individuals and it was again unthinkable that, if the split had occurred as much as a hundred years ago, the same individuals would have been born in the two worlds—the same gametes, under different circumstances, still uniting to form the same zygotes.

The split must—of course!—have occurred when the nightmare-increase began in World I. About thirty years ago.

But—Thorn's credulity almost rebelled—would it have been possible for two worlds to become so different in a short time? Freedom in one, tyranny in the other. Decent people in one, emotional monsters and cringing, embittered underlings in the other. It was horrible to think that human nature, especially the nature of people you loved and respected, could be so much the toy of circumstance.

And yet—the modern world was keyed for change. Wars could, had, come overnight. Sweeping technological changes had been accomplished in a few months. And granting such an immense initial difference as the decision to keep subtronic power a government secret in World II, to make it public property in World I—

Moreover, there was a way of testing. Without pausing to consider, Thorn said, "Remember when we were children? We used to play together. Once we swore an oath of undying friendship."

Clawly II twisted toward him in the current, which was now taking them up past winking corridor entries.

"You are breaking," he remarked in surprise. "I never expected a play for sympathy. Yes, of course I remember."

"And then about two years later," Thorn plunged on, "when our glider dropped in the lake and I was knocked out, you towed me ashore."

Clawly II laughed, but the puzzled look around his eyes deepened. "Did you really believe I saved you? It hardly fits with your behavior toward me afterwards. No, as I think you know, I swam ashore. That was the day on which I first realized that I was I, and that everything and everybody else was circumstances."

Thorn shivered, as much in horror of this changeling beside him as in satisfaction at having checked the date of the time-split. Then he felt revulsion rising in him, more from the body he occupied than from his own thoughts.

"There isn't room in the world for even two people with that attitude," he heard himself challenge bitterly.

"Yes, but there is room for one," Clawly II replied laughingly. Then he frowned and continued hesitatingly, as if against his better judgment. "Look, why don't you try the same thing? Your only chance with the Servants is to make yourself useful to them. Remember, they too are just something to be adjusted to."

For a moment it seemed to Thorn as if Clawly I were striving to look through the eyes of Clawly II. As he tried to gain control of the baffling jumble of emotions this sensation produced, Clawly II took him by the arm and steered them into the slower periphery of the current, then into a dead-current area before the mouth of a short pedestrian corridor.

"No talk from here on," he warned Thorn. "But remember my advice."

There were calculatingly-eyed guards inside the corridor mouth, but again a mere "With a person for the Servants" passed them in.

A low, gray door, without numeral or insignia, blocked the end of the corridor. Some yards short of it was a narrow side-door. Clawly II touched something and the side-door opened. Thorn followed him through it. After a few paces down a dim, curving passageway, they came to a large room, but Clawly II stopped them just short of it. Again he touched something. A door slid silently out of the wall behind them, changing the end of the passageway into a dark niche in the room ahead. Signing to Thorn that they were to wait and watch, Clawly II leaned back with a slow speculative smile.

It was a notably bare room, smaller and lower-ceilinged than he had expected. It was furnished with ostentatious simplicity, and nothing broke the gray monotony of the walls.

Around the longer side of a kidney-shaped table, eleven men sat on stools. Their gray tunics, though clean, were like those of beggars. They were all old, some bald, some capped with close-cropped white or gray. They all sat very erect.

The first thing that struck Thorn—with surprise, he realized—was that the Servants of the People looked in no way malignant, villainous, or evil.

But looking at them a second time, Thorn began to wonder if there was not something worse. A puritanic grimness that knew no humor. A suffocating consciousness of responsibility, as if all the troubles of the world rested on their shoulders alone. A paternal aloofness, as if everyone else were an irresponsible child. A selflessness swollen to such bounds as to become supreme selfishness. An intolerable sense of personal importance that their beggarly clothes and surroundings only emphasized.

But Thorn had barely gleaned this impression, had had no time to survey the faces in detail, except to note that one of two seemed vaguely familiar, when his attention became rivetted on the man who was standing on the other side of the table, the focus of their converging eyes.

That man was obviously one of them. His manner and general appearance were the same.

But that man was also Conjerly.

He was speaking. "I must return at once. The soporific I inhaled into my other body will wear off shortly, and if the other mind becomes conscious, exchange will be difficult. True, Tempelmar is on guard there and could administer another dose. But that is dangerous. Understand, we will attempt no further exchanges unless it becomes necessary to transmit to you information of vital importance. The process is too risky. There is always the possibility of the mental channels being blocked, and one or both of us being marooned here."

"You are wise," observed the midmost of the Servants, apparently their chairman, a tall thin man with wrinkle-puckered lips. "No further exchanges should be necessary. I anticipate no emergencies."

"And so I take my leave," Conjerly continued, "assured that the transtime machine is ready and that the invasion will begin in three days, at the hour agreed. We will prevent the World Executive Committee from taking any significant action until then."

Thorn leaned forward, half guessing what was coming. Clawly II's hand touched his sleeve.

Conjerly bowed his head, stood there rigid. Two black-uniformed guards appeared and took up positions close to him, one on either side.

For a full half minute nothing happened.

Then a great shiver went through Conjerly. He slumped forward, would have fallen except for the two guards. He hung in their arms, breathing heavily.

When he raised his face, Thorn saw that it had a different expression, was that of a different man. A man who looked dazed and sick.

"Where—? Who?" he mumbled thickly. The guards began to lead him out. Then his eyes cleared. He seemed to recognize the situation. "Don't lock me up. Let me explain," he cried out, his voice racked by a desperate yet hopeless urgency. "My name's Conjerly. I'm a member of the World Executive Committee." His face, twisted back over his shoulder, was a white, uncomprehending mask. "Who are you? What do you want out of me? Why am I drugged? What have you done to my body? What are you trying to do to my mind? What—"

The guards dragged him out.

The wrinkle-lipped chairman lowered his eyes. "A distressing occurrence. But, of course, strictly necessary. It is good to think that, when we have things under control in the other world, no such confinements and withholdings of permissible information will have to be practiced—except, of course, in the case of hopeless Recalcitrants."

The others nodded silently. Then Thorn started, for from beside him came an amused, incredulous snicker—not a polite or pleasant sound, and certainly unexpected.

All eyes were turned in their direction.

Clawly II strode out leisurely.

"What did your laughter signify?" The chairman asked sharply, without preliminaries, a look of displeasure settling on his face. "And who is that you have smuggled into our council, without informing us? Let me tell you, some day you will go too far in your disregard of regulations."

Clawly II ignored the second question—and the comment. He swaggered up to the table, planted his hands on it, looked them over, and said, "I laughed to think of how sincerely you will voice your distress when you discover all inhabitants of the other world to be hopeless Recalcitrants—and take appropriate measures. Come, face circumstances. You will be forced to destroy most of the inhabitants of the other world, and you know it."

"We know nothing of the sort," replied the chairman coldly. "Take care that your impudent and foolish opinions do not make us lose confidence in you. In these critical times your shrewdness and ingenuity are valuable to us. You are a useful tool, and only imprudent men destroy a tool because its mannerisms annoy them. But if, in your foolhardy opinionatedness you cease to be useful—that is another matter. As regards the misguided inhabitants of the other world, you very well know that our intentions are the best."

"Of course," agreed Clawly II, smiling broadly, "but just consider what's actually going to happen. In three days the transtime machine will subtronically isolate and annihilate a spatio-temporal patch in this world, setting up stresses which cannot be relieved by any redistribution of material in this world; accordingly the lacuna will find with the corresponding patch from the other world, thereby creating an area common to both worlds. Through this common area your armed forces will pour. They will come as invaders, awakening horror and fear. They will have the element of surprise on their side, but there will inevitably be resistance—organized in desperate haste, but using improvised subtronic weapons. Most important, that resistance will not come, as it would in this world, from a small elite directing an ignorant multitude, but from a people of uniformly high education—a people used to freedom and adverse to submitting to any autocratic government, no matter how well-intentioned. That resistance will not cease until the other world has been destroyed in subtronic battle, or you are forced to destroy it subtronically yourselves and retire through the gap. All that is painfully clear."

"It is nothing of the sort," replied the chairman in measured and dispassionate tones. "Our invasion will be well-nigh bloodless, though we must prepare for all eventualities. At the proper moment Conjerly and Tempelmar will seize control of the so-called World Executive Committee, thereby preventing any organized resistance at the fountainhead. The majority of inhabitants of the other world have no technical knowledge of subtronic power and will therefore constitute no danger. Ultimately they will be grateful to us for insuring the safety of their world and protecting them from their irresponsible leaders. It will only be necessary for us to capture and confine all technicians and scientists having a knowledge of subtronic physics. To do this, we must admittedly be ready to take any and all necessary steps, no matter how unpleasant. For our main purpose, of which we never lose sight, is always to keep the knowledge of subtronic power—which now imperils two worlds—in the possession of a small, responsible, and benevolent elite."

Thorn shivered. The horrible thing was that these Servants actually believed that they were acting for the best, that they had the good of mankind—of two mankinds—at heart.

"Exactly," said Clawly II, continuing to smile. "The only thing you don't see, or pretend not to see, is the inevitable consequences of that main purpose. Even now your secrets are gravely endangered. Mind-exchange is putting more and more Recalcitrants and Escapists into the other world. It is only a matter of time before some of them begin to realize that the inhabitants of that world are their potential allies rather than their foes, and join forces with them. Similarly it is only a matter of time until the mind of a subtronic technician is displaced into this world and contacted by the Recalcitrants here—then you will have to fight subtronic wars in two worlds. Your only chance, as I'm glad you recognize in part, is to strike hard and fast, destroy the other world, along with all the Recalcitrants and Escapists who have entered it, then seek out and eliminate all displaced minds in this world. Your weakness is in not admitting this at the start. Everything would be much easier if you would leave out pseudobenevolent intentions and recognize that you are up against an equation in destruction, which you must solve in the only logical way possible—by a general canceling out."

And he rocked back on his heels a little, again surveying the eleven old faces. It struck Thorn that thus legendary Loki must have mocked the Dawn Gods and flayed their high-sounding pretenses, confident that his cunning and proven usefulness would protect him from their wrath. As for the Servants, their paternalism was unpleasantly apparent in their attitude toward Clawly II. They treated him like a brilliantly mischievous favorite child—always indulged, often threatened, seldom punished.

Certainly there was a germ of greatness about this Clawly II. If only he had Clawly I's sane attitude toward life, so that his critical thinking would come to something more than mere sardonic jibing!

One thing was certain, Clawly II's claim that he wanted to float on the stream of life was a gross understatement. What he really wanted was to dance along a precipice—and this time, apparently, he had taken one heedless step too many.

For the chairman looked at him and said, "The question arises whether your insistence on destruction has not assumed the proportions of a mania. We will at once reconsider your usefulness as a tool."

Clawly II bowed. He said smoothly, "First it would be well to interview the person I have brought you. You will be pleased when I tell you who he is." And he motioned to Thorn.

All eyes turned on the niche.

Abruptly, painfully, Thorn woke from his impersonal absorption in the scene unrolling before him. Again it came to him, like a hammer blow, that he was not watching from the safety of a spy-hole, but was himself immediately and fatally involved. Again the urge to escape racked him—with redoubled force, because of the warning that he must now at all costs take back to World I. It was such a simple thing. Just a change of viewpoints. He had seen Conjerly accomplish it. Surely, if he concentrated his mind in the right way, it would be that other Thorn who walked forward to face the Servants and the destiny of that other Thorn's own making, while he sank back. Surely his need to warn a world would give him sufficient impetus.

But all the time he was walking toward the table. It was his dragging feet that scuffed the gray flooring, his dry throat that swallowed, his cold hands that clenched and unclenched. The eleven old faces wavered, blurred, came clear again, seemed to swell, grow gray and monstrous, become the merciless masks of judges of some fabled underworld, where he must answer for another man's crimes.

The table stopped his forward progress. He heard Clawly II say, "I am afraid that I am still very useful to you. Here is your chief enemy, brought to book by my efforts alone. He was part of our bag when he raided the local Recalcitrant headquarters last night. He escaped and took to the hills, where I personally recaptured him—the Recalcitrant leader Thorn 37-P-82."

But the Servants' reaction could not have been the one Clawly was expecting, for the old faces registered anger and alarm. "Irresponsible child!" the chairman rapped out. "Didn't you hear what Conjerly reported—that he is certain there has occurred a mind exchange between the Thorns? This man is not the Recalcitrant, but a displaced mind come to spy on us. You have provided him with what he wanted—an opportunity to learn our plans."

Thorn felt their converging hostility—a palpable force. His mind shrank back from the windows of his eyes, but, chained there, continued to peer through them.

The chairman's wrinkled hand dropped below the table. He said, "There is only one course of action." His hand came up, and in it a slim gleaming cone. "To eliminate the displaced mind before a re-exchange can be—"

Thorn was dimly conscious of Clawly II leaping forward. He heard him begin, "No! Wait! Don't you see—"

But although that was all he heard, he knew what Clawly II was going to say and why he was going to say it. He also knew why Thorn II had been able to exchange with him when Thorn II thought he was trapped and facing death on the rooftop. He knew that the chairman's action was the very thing that would nullify the chairman's purpose. At last he had found the sufficient impetus—it was staring at him down the slim, gleaming cone, leering at him even as the chains broke and his mind dropped back from the windows of his eyes into a black, dimensionless pit.

The fear of death.

Thorn did not ask himself why his resting place was dark and stuffy, rocky and dry, or where the stale, sour smell of woodsmoke came from. He was content to lie there and let his mind snuggle down into his body, lull itself with simple sensations, forget the reverberations of its terrible journey. World II still clung to him sluggishly. But like a nightmare from which one has wakened, it could be disregarded.

In a moment he would rouse himself and do what must be done. In a moment, he knew, he would know no peace until the warning had been given and all essential steps taken, until the invasion had been met and decisively thrown back. He would be a creature of tension, of duty, of war.

But for the moment nothing mattered, nothing could break his sense of peace.

Odd, though, that the heavy woodsmoke did not make him cough, and that his body was not aching from its cramped position and rocky crouch.

Muffledly, as if its source were underground, came a distant howling, melancholy and long-drawn-out, ending on a low note of menace.

He started up. His shielding hand encountered a low ceiling of rock, hurriedly traced it to jagged, sloping walls on either side.

It was he that was underground, not the howling.

What the devil had Thorn II been doing in a cave in World I? Why was he wearing this odd jumble of heavy clothing, that seemed to include thick, stiff boots and furs? Where had he gotten the long knife that was stuck in his belt?

The cramping darkness was suddenly full of threats. In panicky haste he continued his feeling-out of the walls, found that he was in a small domed chamber, high enough in the center so that he could almost stand upright. On three sides the walls extended down to the uneven floor, or to the mouths of horizontal crevices too narrow to stick more than an arm in.

On the fourth side was a low opening. By getting down on hands and knees he could wriggle in.

It led slightly upward. The smell of woodsmoke grew heavier. After two sharp turns, where jagged edges caught but did not tear his heavy clothing, he began to see the gray gleam of daylight.

The roof of the passageway grew higher, so that he could almost walk upright. Then it suddenly opened into a larger chamber, the other end of which was completely open to a gloomy landscape.

This landscape consisted of a steep hillside of granite boulders and wind-warped pines, all patched with snow, at a middle distance, as if across a ravine.

But Thorn did not inspect it closely, for he was looking chiefly at the fire blocking the mouth of the narrow passageway, sending up smoke that billowed back from the ceiling, making the day even more gloomy and dim.

It immediately struck him as being a very remarkable fire, though he couldn't say why. After a while he decided that it was because it had been very cleverly constructed to burn steadily for a long time, some of the logs and branches being so placed that they would not fall into the fire until others had been consumed. Whoever had built that fire must have painstakingly visualized just how it was going to burn over a period of several hours.

But why should he waste time admiring a fire? He kicked it aside with the clumsy boots Thorn II had dug up God knows where, and strode to the mouth of the cave.

Claws skirred on rock, and he had the impression of a lithe furry animal whisking off to one side.

The cave opened on a hillside, similar to the one opposite and slanting down to a twisting, ice-choked stream. Overhead a gray, dreary sky seemed to be trending toward nightfall. The walls of the ravine shut off any more distant horizon. It was very cold.

The scene was hauntingly familiar.

Had Thorn II been insane, or gone insane? Why else should he have hidden himself in a cave in a near-arctic wild-life reserve? For that certainly seemed to be what he had done, despite the difficulty in picturing just how he had managed to do it in so short a time.

A fine thing if, after getting back to his rightful world, he should starve to death in a reserve, or be killed by some of the formidable animals with which they were stocked.

He must climb the hill behind him. Wherever he was, he'd be able to sight a beacon or skylon from its top.

It suddenly occurred to him that this ravine was devilishly like one in the woodland near the symchromy amphitheater, a ravine in which he and Clawly used to go exploring when they were boys. There was something unforgettably distinctive about the pattern of the streambed.

But that couldn't be. The weather was all wrong. And that ravine was much more thickly wooded. Besides, erosion patterns were always repeating themselves.

He started to examine the queer, bulky clothing Thorn II had been wearing. In doing so, he got one good look at his hands—and stopped.

He stood for a long moment with his eyes closed. Even when soft paws pattered warily somewhere over his head and a bit of gravel came trickling down, he did not jerk.

Rapidly the determination grew in his mind that he must get to the hilltop and establish his position before he did anything else, before he thought anything else, certainly before he examined his hands or his face more closely. It was more a terror-inspired compulsion than a determination. He stepped to the rocky lip in front of the cave, and looked back. Again there was the impression of a gray, furry animal streaking for cover. Something about the size of a cat. He hurriedly surveyed the routes leading upward, picked one that seemed to slope more gradually and avoid the steeper barren stretches, and immediately started up it at a scrambling trot, his eyes fixed resolutely ahead.

But after he had gone a little way, he saw something that made him stop and stare despite the compulsion driving him.

On a pine-framed boulder about a dozen yards ahead, to one side of the route he was taking, three cats sat watching him.

They were cats, all right, house cats, though they seemed to be of a particularly thick-furred breed.

But one wouldn't normally find house cats on a wild-life reserve. Their presence argued the nearness of human habitation. Moreover, they were eying him with a poised intentness that indicated some kind of familiarity, and did not fit with their earlier racing for cover—if those had been the same animals.

He called, "Kitty!" His voice cracked a little. "Kitty!"

The sound drifted thinly across the hillside, as if congealed by the cold.

And then the sound was answered, or rather echoed, by the cat to the right, a black and gray.

It was not exactly the word "Kitty" that the cat miowed, but it was a sound so like it, so faithful to his exact intonations, that his flesh crawled.

"Kii ... eee." Again the eerily mocking, mimicking challenge rang out.

He was afraid.

He started forward again. At the first scrape of his boots on gravel, the cats vanished.

For some time he made fast, steady progress, although the going was by no means easy, sometimes leading along the rims of landslides, sometimes forcing him to fight his way through thick clumps of scrub trees. The last "Kii ... eee" stuck in his ears, and at times he was pretty sure he glimpsed furry bodies slipping along to one side, paralleling his progress. His thoughts went off on unpleasant tacks, chiefly about the degree to which careful breeding had increased the intelligence of house cats, the way in which they had always maintained their aloof and independent life in the midst of man's civilization, and other less concrete speculations.

Once he heard another sound, a repetition of the melancholy howling that had first startled him in the cave. It might have been wolves, or dogs, and seemed to come from somewhere low in the ravine and quite a distance away.

The sky was growing darker.

The rapid ascent was taking less out of him than he would have imagined. He was panting, but in a steady, easy way. He felt he could keep up this pace for a considerable distance.

The pines began to thin on the uphill side. He emerged onto a long, wide slope that stretched, ever-steepening, boulder-strewn but almost barren of vegetation, to the ravine's horizon. His easiest way lay along its base, past tangled underbrush.

A little distance ahead and up the slope, a large chunk of granite jutted out. On its rim sat three cats, again regarding him. Something about the way they were turned toward each other, the little movements they made, suggested that they were holding a conference and that the topic of the conference was—he.

From behind and below the howling came again. The cats pricked up their ears. There were more movements, more glances in his direction. Then as he began jogging along again, one of the cats—the tiger—leaped down and streaked away past him, downhill. While the black-and-gray and the black dropped off the granite rim more leisurely and began to trot along in the direction he was taking, with frequent sidewise glances.

He quickened his pace, grateful for the reserve energy.

The going was good. There were no eroded chutes to be edged around, no pines to fight.

Once the howling was repeated faintly.

The shadowy bodies of the cats slipped between the boulders, in and out. Gradually he began to draw ahead of them.

For some reason everything felt very natural, as if he had been created for this running through the dusk.

He sprinted up the last stretch, came out on top.

For a long time he just looked and turned, and turned and looked. Everything else—emotions, thought—was subordinated to the act of seeing.

Up here it was still pretty light. And there were no hills to shut out the view. It stretched, snow-streaked, lightless, lifeless, achingly drear, to black horizons in three directions and a distant glittering ice-wall in the fourth.

The only suggestion of habitation was a thin pencil of smoke rising some distance across the plateau he faced.

For as long as he could, he pretended not to recognize the ruins sparsely dotting the landscape—vast mountainous stumps of structures, buckled and tortured things, blackened and ice-streaked, surrounded by strange formations of rock that suggested lava ridges, as if the very ground had melted and churned and boiled when those ruins were made.

A ruined world, from which the last rays of a setting sun, piercing for a moment the smoky ruins, struck dismal yellow highlights.

But recognition could only be held at bay for a few minutes. His guess about the ravine had been correct. That snow-shrouded, mile-long mound ahead of him was the grave of the Opal Cross. That dark monolith far to the left was the stump of the Gray H. Those two lopped towers, crazily buckled and leaning toward each other as if for support, were the Gray Twins. That split and jagged mass the other side of the ravine, black against the encroaching ice, up-thrust like the hand of a buried man, was the Rusty T.

It could hardly be World I, no matter after what catastrophe or lapse of years. For there was no sign, not even a suggestive hump, of the Blue Lorraine, the Mauve Z, or the Myrtle Y. Nor World II, for the Black Star's ruins would have bulked monstrously on the immediate left.

He looked at his hands.

They were thickened and calloused, ridged and darkened by scars of wounds and frostbite, the nails grained and uneven. And yet they were Thorn's hands.

He lifted them and touched his chapped, scaly face, with its high-growing, uncombed beard and long hair matted against his neck under the fur hood.

His clothes were a miscellany of stiff, inexpertly-tanned furs, portions of a worn and dirty suit of flying togs, and improvised bits of stuff, such as the hacked-out sections of elastoid flooring constituting the soles of his boots.

His heavy belt, which was reinforced with reading-tape, supported two pouches, besides the knife, which seemed to be a crudely-hilted cutter from a hyperlathe.

One of the pouches contained a sling shot powered by strips of elastoid, several large pebbles, and three dark, dubious chunks of meat.

In the other were two small containers of nutriment-concentrate with packaging-insignia of twenty-five years ago, a stimulol cannister with one pellet left, two bits of sharp metal, a jagged fragment of flint, three more pieces of elastoid, more reading-tape, a cord made of sinew, a glastic lens, a wood carver's handsaw, a small, dismantled heat-projector showing signs of much readaptive tinkering, several unidentifiable objects, and—the smooth gray sphere he had stolen at the Yggdrasil.

Even as he was telling himself it could not be the same one, his blunt fingers were recognizing its unforgettable smoothness, its oblate form, its queerly exaggerated inertia. His mind was remembering he had fancied it a single supergiant molecule, a key—if one knew how to use it—to the doors of unseen worlds.

But there was only time to guess that the thing must be linked to his mind rather than to any of the bodies his mind had occupied, and to wonder how it had escaped the thorough search to which he had been subjected in the Black Star, when his attention was diverted by a faint eager yapping that burst out suddenly and was as suddenly choked off.

He turned around. Up the boulder-studded slope he had just ascended, streaming out of the underbrush at its base, came a pack of wolves, or dogs—at least thirty of them. They took the same sloping course that he had taken. There was a strange suggestion of discipline about their silent running. He could not be sure—the light was very bad—but he fancied he saw smaller furry shapes clinging to the backs of one or two of them.

He knew now why he had spent time admiring a fire.

But the pack was between him and that fire, so he turned and ran across the plateau toward where he had glimpsed the rising wisp of smoke.

As he ran he broke out and chewed the lone stimulol pellet, breathing thanks to that Thorn—he would call him Thorn III—who had hoarded the pellet for so many years, against some ultimate emergency.

He ran well. His clumsily-booted feet avoided rocks and ruts, hit firmly on icy patches, with a sureness that made him wonder if they did not know the route. And when the stimulol hit his blood-stream, he was able to increase speed slightly. But risking a look back, he saw the pack pouring up over the crest. A steady baying began, eager and mournful.

In the growing darkness ahead a low, ruddy, winking light showed. He studied its slow increase in size, intent on gauging the exact moment when he would dare to sprint.

The way became rougher. It was a marvel how his feet carried him. The ruddy light became a patch, illumining a semicircular opening behind it. The baying drew near. He could hear the scuff of clawed feet. He started to sprint.

And just in time. There was a great brown hound springing higher than his shoulder, snapping in at his neck, splashing it with slaver, as he jumped the fire, turned with his whipped-out knife, and took his stand beside the gnarled man with the spear, in front of the doorless doorway of the half-buried room, or large crate, of weathered plastoid.

Then for a moment it was chaotic battle—gaunt-bellied forms rearing above the flames—red eyes and clashing yellow fangs—spear and cutter licking out—reek of singed hair—snarls, squeals, grunts, gasps—and, dominating it all, making it hellish, those three spitting, mewing cat-faces peering over the shoulders of three dogs that hung in the rear.

Then, as if at a note of command, the dogs all retreated and it was suddenly over. Without a word, Thorn and the other man began to repair and restock with fuel the scattered fire. When it was finished, the other man asked, "Did they get you anywhere? I may be crazy, but I think the devils are starting to poison the teeth of some of the hounds."

Thorn said, "I don't think so," and began to examine his hands and arms.

The other man nodded. "What food you got?" he asked suddenly.

Thorn told him. The other man seemed impressed by the nutriment-concentrate. He said, "We could hunt together for a while, I guess. Ought to work out good—having one watching while the other sleeps." He spoke rapidly, jumbling the words together. His voice sounded disused. He studied Thorn uneasily.

Thorn studied him. He was smaller and moved with a limp, but beard, skin, and clothing were like Thorn's. The screwed-up face was not familiar. The darting, red-rimmed eyes below the jutting brows were not altogether sane. Thorn's presence seemed to put him on edge, to shake his emotions to the core. Every time he snapped shut his cracked, nervous lips, Thorn felt that he dammed up a torrent of babblingly eager talk.

He asked Thorn, "Where did you come from?"

"A cave in the ravine," Thorn replied, wondering how much to tell. "What's your story?"

The man looked at him queerly. He trembled. Then the cracked lips opened.

To Thorn, squatting there behind the crackling fence of flame, staring out into a night that was black except for the occasional red hint of eyes, it seemed that what he heard was what he had always known.

"My name was Darkington. I was a geology student. What saved me was that I was in the mountains when the power broke loose. I guess we all knew about the power, didn't we? It was in the air. We'd always known that some day someone would find out what it was behind gravity and electricity and magnetism"—he stumbled over the long words—"and the more they tried to hush it up, the surer we were that someone had found out. I guess they shouldn't have tried to hush it up. I guess intelligent creatures can't back out of their destiny like that.

"But anyway I was in the mountains when the power broke loose and ate up all the metal it could reach. Our party was laid up by the fumes, and two of them died. Afterwards some of us started out to try to contact other survivors, but the fumes were worse where we went and some more died and the rest broke up. I got in with a gang that was trying to make a go of farming just north of the volcano belt, but we made a lot of mistakes and then came the first of the long winters and finished off all our plans and made us realize that the weather had all gone different, what with the exposed raw rock taking all the carbon dioxide out of the air, and not enough green stuff left to replace it. After that I drifted around and took up with different scavenging gangs, but when the cannibalism started and the cats and dogs began to get really dangerous, I headed north and made it to the glaciers. Since then I've just hung on, like you see me."

He turned to Thorn. Already his voice was hoarse. Like nervous hunger, his eagerness to talk had not carried him far.

Thorn shook his head, peering beyond the fire. "There must be a way," he said slowly. "Admittedly it would be difficult and we'd risk our lives, but still there must be a way."

"A way?" the other asked blankly.

"Yes, back to wherever men are beginning to band together and rebuild. South, I suppose. We might have to hunt for a long time, but we'd find it."

There was a long silence. A curious look of sympathy came into the other man's face.

"You've got the dreams," he told Thorn, making his croaking voice gentle. "I get them myself, so strong that I can make myself believe for a while that everything's the way it was. But it's just the dreams. Nobody's banding together. Nobody's going to rebuild civilization, unless"—his hand indicated something beyond the fire—"unless it's those devils out there."

Alternate waves of guilt and almost unbearable excitement washed Clawly I as he hurried through the deserted corridors of the Blue Lorraine toward the office of Oktav. In grimmest seriousness he wondered whether his own fancied role of mad Pied Piper had not come true, whether his mind—and those of Firemoor and his other accomplices in the Martian hoax—were not already more than half usurped by diabolically mischievous mentalities whose only purpose, or pleasure, was to see a sane world reduced to chaos.

For the faked threat of a Martian invasion was producing all the effects he could ever have anticipated, and more, as the scenes he had just been witnessing proved. They stuck in his mind, those scenes. The air around the Blue Lorraine aswarm with fliers from bullet-swift couriers to meddlesome schoolchildren. Streams of machine-units and various materials and supplies going out on subtronic currents for distribution to selected points in the surrounding countryside, for it had early become apparent that the skylons were exceedingly vulnerable to attack from space—all Earth's eggs in a few thousand baskets. Engineers busy around the Blue Lorraine's frosty summit, setting up energy-projectors and other improvised subtronic artillery—for although the skylons were vulnerable, they were the proud symbols and beloved homes of civilization and would be defended to the last. All eyes craned apprehensively upward as a thundering spaceship burst through the blue sky, then lowered in ruefully humorous relief as it became obvious that it was, of course, no alien invader, but one of Earth's own ships headed for the nearby yards to be fitted with subtronic weapons. All eyes turned momentarily to the west, where defensive screens were being tried out, to watch a vast iridescent dome leap momentarily into being and a circle of woodland puff into smoke. Excited eyes, all of them, as ready to flash with humor as to betray shock, anxiety, or fear. Eyes that were seven-eighths "There probably won't be any invasion" and one-eighth "There will be." Eyes that made Clawly proud of mankind, but that also awakened sickening doubts as to the wisdom of his trickery.

And to think that this sort of thing was going on all over the world. The use of subtronic power in transport and fabrication made possible a swiftness in preparation never before known in Earth's history. Organization was a weak point, the Earth being geared for the leisurely existence of peace and individual freedom, but various local agencies were taking over while the World Executive Committee created the framework of a centralized military authority. Confusedly perhaps, and a little bunglingly, but eagerly, wholeheartedly, and above all swiftly, Earth was arming to meet the threat.

It was all so much bigger than anyone could have anticipated, Clawly told himself for the hundredth time, unconsciously increasing his already rapid pace as he neared Oktav's office. He had started it all, but now it was out of his hands. He could only wait and hope that, when the real invasion came, across time rather than space, the present preparations would prove useful to Earth's bewildered defenders. In any case, a few hours would tell the story, for this was the third day.

But what if the transtime invasion did not come in three days? The hoax might be uncovered at any moment now—Firemoor was already regretting the whole business, on the verge of a funk—and during the period of angry reaction no invasion reports of any sort would be believed. Then he would be in the position of having cried wolf to the world.

Or what if the transtime invasion did not come at all? All his actions had been based on such insubstantial evidence—Thorn's dream-studies, certain suggestive psychological aberrations, the drugged Conjerly's murmur of "... invasion ... three days...." He was becoming increasingly convinced that he would soon wake, as if from a nightmare, and find himself accused as a madman or charlatan.

Certainly his nerves were getting out of hand. He needed Thorn. Never before had he realized the degree to which he and Thorn were each other's balance wheel. But Thorn was still missing, and the inquiry agencies had no progress to report. Despite the larger anxieties in which his mind was engulfed, Thorn's absence preyed upon it to such a degree that he had twice fancied he spotted Thorn among the swirling crowd outside the Blue Lorraine.

But even more than he needed Thorn, he needed Oktav. Now that the crisis had come, he could see to what an extent the seer's advice had determined all his actions, from his first serious belief in the possibility of transtime invasion to his engineering of the Martian hoax. Call it superstition, ignorant credulity, hypnotism, the fact remained that he believed in Oktav, was convinced that Oktav had access to fields of knowledge undreamed of by ordinary men. And now that Oktav was gone, he felt an increasing helplessness and desperation, so that he could not resist the impulse driving him back once more to the cryptically empty office.

As he raised his hand to activate the door, memories came stealing eerily back—of former sessions in the room beyond, of the last session, of Oktav's strange summoner clad in the garments of Dawn Civilization, of the inexplicable disappearance of summoner and summoned in the exitless inner chamber.

But before his hand could activate the door, it opened.

Clad in his customary black robe, Oktav was sitting at his desk.

As if into a dream within a dream, Clawly entered.

Although the seer had always seemed supernaturally ancient, Clawly's first impression was that Oktav had vastly aged in the past three days. Something had happened to drain his small remaining store of life forces almost to the last drop. The hands were folded white claws. The face was wrinkle-puckered skin drawn tight over a fragile skull. But in the sunken, droopingly lidded eyes, knowledge burned more fiercely than ever. And not knowledge alone, but also something new—a reckless determination to use that knowledge. It was a look that made Clawly shiver—and thrill.

All the questions that had pounded at his brain so long, waiting for this interview, were suddenly mute.

"I have been on a far journey," said the seer. "I have visited many worlds that were supposed to be dead, and have seen what strange horrors can result when mere men seek to make wise use of a power befitting only a god or creatures like gods. I have gone in constant danger, for there are those against whom I have rebelled and who therefore seek my life, but I am safe from them for a time. Sit down, and I will tell you what is in my mind."

Clawly complied. Oktav leaned forward, tapping the desk with one bone-thin finger.

He continued, "For a long time I have spoken to you in riddles, dealt with you vaguely, because I was trying to play a double game—impart essential information to you, and yet not impart it. That time is past. From now on I speak clearly. In a little while I shall depart on a desperate venture. If it succeeds, I do not think you will have to fear the invasion threatening your world. But it may fail, and therefore I must first put at your disposal all the information I possess, so that you can judge how best to act in that event."

He looked up quickly. Clawly heard movement in the corridor. But it was from the inner chamber that the sudden interruption came.

Once again Oktav's summoner stood in the inner doorway. Once again that young-old, ignorant-wise, animal-god face was turned on Oktav. The muscles of the clamped jaw stood out like knobs. One arm in its cylinderlike sleeve of stiff, ancient fabric, was rigidly extended toward the seer.

But Clawly had only time for the barest glance, and Oktav had even less—he was just starting to turn and his eyes were only on the verge of being lighted with a flicker of recognition—when a great tongue of softly bluish flame licked out from the summoner's hand and, not dying as flames should, folded around Oktav like a shroud.

Before Clawly's eyes, Oktav's robe burst into flame. His body shriveled, blackened, contorted in agony, curling like a leaf. Then it was still.

The soft flame returned to the summoner's hand.

Incapable of motion or connected thought or any feeling but a sick dismay, Clawly watched. The summoner walked over to Oktav's desk—clumsily, as if he were not used to dealing with three-dimensional worlds, but also contemptuously, as if worlds of three or any other number of dimensions were very trivial affairs to him. He extracted from the charred remains of Oktav's robe a small gray sphere, which Clawly now saw was similar to one which the summoner had been holding in his outstretched hand. Then, with an equal clumsiness and contempt, with a sweeping glance that saw Clawly and ignored him, the summoner walked back through the inner doorway.

Clawly's body felt like a sack of water. He could not take his eyes off the thing behind the desk. It looked more like a burnt mummy than a burnt man. By some chance the blue flame had spared the high forehead, giving the face a grotesquely splotched appearance.

The outer door was opened, but Clawly did not turn or otherwise move. He heard a hissing inhalation—presumably when the newcomer saw the hideous corpse—but the newcomer had to come round in front before Clawly saw and recognized—or rather, partly recognized—him. And even then Clawly felt no reaction of astonishment or relief, or any reaction he might have expected to feel. The incredible scene he had just witnessed lingered like an after-image, and other thoughts and feelings refused to come into focus. The dead body of Oktav dominated his vision and his mind, as if emanating a palpable aura that blurred everything else.

The newcomer noted the incompleteness of Clawly's recognition, for he said, "Yes, I'm Thorn, but, I think you know, not the Thorn who was your friend, although I am inhabiting his body." To Clawly the words seemed to come from a great distance; he had to fight an insidious lethargy to hear them at all. They continued, "That Thorn is taking my place in the world—and three days ago I rejoiced to think of the suffering he would undergo there. Fact is, I was your enemy—his and yours—but now I'm not so sure. I'm even beginning to think we may be able to help each other a great deal. But I'm responsible for more lives than just my own, so until I'm sure of you, I daren't take any chances. That's the reason for this."

And he indicated the small tubular object in his hand, which seemed to be the dismantled main propulsion unit of a suit of flying togs—a crude but effective short-range blaster.

Clawly began to take him in, though it was still hard for him to see anything but the thing behind the desk. Yes, it was Thorn's face, all right, but with a very uncharacteristic expression of stubborn and practical determination.

The newcomer continued, "I've been following you because Thorn's memoranda tapes showed that you and he were working together in what seemed to be an effort to warn this world of its danger. But lately things have been happening that make me doubt that—things I want explained. What's this Martian invasion? Is it real? Or an attempt to rouse your world into a state of preparedness? Or a piece of misdirection designed to confuse the issue and make the Servant's invasion easier? Then, why did you come here, and who is this creature, and how did he die?" With a gesture of repugnance, he indicated the body of Oktav. "What I overheard reawakened my old suspicion that there's somebody behind this business of duplicate worlds, somebody who's making a profit from it, somebody—"

His voice went dead. In an instant, all the frowning concentration blanked out of his face. Very slowly, like a man who suddenly becomes aware that there is a monster behind him, he began to turn around.

At the same time, Clawly felt himself begin to shake—and for the same reason.

It was a very small and ordinary thing—just a small cough, a dry clearing of the throat. But it came from behind the desk.

The shriveled, scorched body was swaying a little; the charred hands were pushing across the desk, leaving black smears; a tremor was apparent in the blackened jaw.

For a moment they only watched in horror. Then, drawn by the same irresistible impulse, they slowly approached the desk.

The blind, ghastly movements continued. Then the burnt lips parted, and they heard the whisper—a whisper that was in every syllable a hard-won victory over seared tissues.

"I should be dead, but strange vitalities linger in him who has possessed a talisman. My eyes are embers, but I can dimly see you. Come closer, that I may say what must be said. I have a testament to make, and little time in which to make it, and no choice as to whom it is made. Draw nearer, that I may tell you what must be done for the sake of all worlds."

They obeyed, sweat starting from their foreheads in awe of the inhumanly sustained vitality that permitted this charred mummy to speak.

"Purely by chance, a man of the Dawn Civilization discovered a talisman—a small nonmechanical engine controlled by thought—giving him the power of traveling in time, and across time, and into the regions beyond time. There it led him to seven other talismans, and to a similar but larger engine of even greater power, which he named the Probability Engine. He took in with him seven accomplices, I being one, and together we used the Probability Engine to split time and make actual all possible worlds, preserving only the best of them, and—so we thought—destroying the rest."

The whisper slowly began to diminish in strength. Clawly and the other leaned in closer to the black, white-foreheaded face.

"But I discovered that those destroyed worlds still exist, and I know too well what mad tinkering the others will be prompted to, when they make the same discovery. You must prevent them, as I intended to. In particular, you must find the Probability Engine and summon its true owners, whatever creatures they may be, who built it and who lost the first talisman. They're the only ones fitted to deal with the tangle of problems we have created. But to find the Probability Engine, you must have a talisman. Ters, who destroyed me, took mine, but that was one which I had stolen. My own original talisman is in the possession of Thorn, the Thorn of this world, who stole it from me, I now believe, because of some unconscious prompting from the True Owners, groping through many-layered reality in an effort to find their lost engine. That Thorn is worlds away from here, more worlds than you suspect. But you"—his fingers fumbled sideways, touching those of the other Thorn, who did not withdraw his hand—"can get into touch ... with him ... through your linked ... subconscious minds." The whisper was barely audible. It was obvious that even the talisman-vitalized strength was drawing to an end. "That talisman ... which he has ... is inert. It takes a key-thought ... to unlock its powers. You must transmit ... the key-thought ... to him. The key-thought ... is ... 'Three botched ... worlds—'"

The whisper trailed off into a dry rattle, then silence. The jaw fell open. The head slumped forward. Clawly caught it, palm to white forehead, and let it gently down on to the desk, where the groping fingers had traced a black, crisscross pattern.

Over it, Clawly's eyes, and those of the other Thorn, met.

The Sky Room of the Opal Cross was so altered it was hard to believe it had been a festivities center only three days ago. The World Map and Space Map still held their dominating positions, but the one was dotted with colored pictorial symbols indicating the location of spaceports and space-yards, defense installations, armament fabrication and conversion centers, regular and emergency power stations, field headquarters, and like military information, while the Space Map, in which a system of perspective realistically conveyed three-dimensional depth, was similarly dotted in the Marsward sector to indicate the real or hypothetic location of spacecraft. This latter map emphasized with chilling clarity the fact that Earth had nothing at all in the way of an interplanetary battle fleet, only a scattering of unarmed or lightly armed exploratory craft that now, by stretching a point, could be counted as scouts. While fanning out from Mars in a great hemisphere, hypothetic but none the less impressive, loomed a vast armada.

The rest of the Sky Room was filled with terraced banks of televisor panels, transmission boards, plotting tables, and various calculating machines, all visible from the central control table around which they crowded. One whole sector was devoted to other military installations and specialized headquarters in the Opal Cross. Other sectors linked the control table with field headquarters, observation centers, spacecraft, and so on.

But now all the boards and tables, save the central one, were unoccupied. The calculating machines were untended and inoperative. And the massed rows of televisor panels were all blank gray—as pointless as a museum with empty cases.

A similar effect of bewildered deflation was apparent in most of the faces of the World Executive Committee around the control table. The exceptions included Chairman Shielding, who looked very angry, though it was a grave anger and well under control; Conjerly and Tempelmar, completely and utterly impassive; Clawly, also impassive, but with the suggestion that it would only take a hairtrigger touch to release swift speech or action; and Firemoor, who, sitting beside Clawly, was plainly ill at ease—pale, nervous, and sweating.

Shielding, on his feet, was explaining why the Sky Room had been cleared of its myriad operators and clerks. His voice was as cuttingly realistic as a spray of ice water.

"... and then," he continued, "when astronomic photographs incontrovertibly proved that there were no alien craft of any sort near Mars—certainly none of the size reported and nothing remotely resembling a fleet, not even any faintly suspicious asteroids or cometary bodies—I hesitated no longer. On my own responsibility I sent out orders countermanding any and all defense preparations. That was half an hour ago."

One of the gray panels high in the Opal Cross sector came to life. As if through a window, a young man with a square face and crisply cropped blond hair peered out. The emptiness of the Sky Room seemed to startle him. He looked around for a moment, then switched to high amplification and called down to Shielding,

"Physical Research Headquarters reporting. A slight variation in spatio-temporal constants has been noted in this immediate locality. The variation is of a highly technical nature, but the influence of unknown spy-beams or range-finding emanations is a possible, though unlikely, explanation."

Shielding called sharply, "Didn't you receive the order countermanding all activities?"

"Yes, but I thought—"

"Sorry," called Shielding, "but the order applies to Research Headquarters as much as any others."

"I see," said the young man and, with a vague nod, blanked out.

There was no particular reaction to this dialogue, except that the studied composure of Conjerly and Tempelmar became, if anything, more marked—almost complacent.

Shielding turned back. "We now come to the question of who engineered this criminally irresponsible hoax, which," he added somberly, "has already cost the lives of more than a hundred individuals, victims of defense-preparation accidents." Firemoor winced and went a shade paler. "Unquestionably a number of persons must have been in on it, mainly members of the Extraterrestrial Service. It couldn't have been done otherwise. But we are more interested in the identity of the main instigators. I am sorry to say that there can be no question as to the identity of at least two of these. The confession of three of the accomplices make it—"

"Co-ordination Center 3 reporting." Another of the Opal Cross panels had flashed on and its perplexed occupant, like the other, was using high amplification to call his message down to Shielding. "Local Power Station 4 has just cut me off, in the midst of a message describing an inexplicable drain on their power supply. Also, the presence of an unknown vehicle has been reported from the main rotunda."

"We are not receiving reports," Shielding shouted back. "Please consult your immediate superior for instructions."

"Right," the other replied sharply, immediately switching off.

"There you see, gentlemen," Shielding commented bitterly, "just how difficult it is to halt a hoax of this sort. In spite of all our efforts, there undoubtedly will be more tragic accidents before minds get back to normal." He paused, turned. "Clawly and Firemoor, what do you have to say for yourselves in justification of your actions, beyond a confession of wanton mischievousness, or—I must mention this possibility too—an attempt to create confusion for the furtherance of some treasonable plot? Remember it is not a matter of accomplices' confessions alone, who might conceivably perpetrate a hoax and then attempt to shift the blame onto blindly gullible and negligent superiors. There is also the testimony of two members of our own committee, who can for the moment remain anonymous—"

"I see no reason for that," drawled Tempelmar.

"Thank you." Shielding nodded to him. "Very well, then. The testimony of Conjerly and Tempelmar." And he turned again toward the accused.

Firemoor looked down at the table and twisted miserably. Clawly returned Shielding's gaze squarely. But before either of them could reply—

"Co-ordination Center 4! Reporting the presence of a group of armed individuals in black garments of an unfamiliar pattern proceeding—"

"Please do not bother us!" Shielding shouted irritably. "Consult your superior! Tell him to refer all communications to Co-ordination Center 1!"

This time the offending panel blanked out without reply.

Shielding turned to a master control board behind him and rapidly flipped off all the beams, insuring against future interruption.

Clawly stood up. His face had the frozenness of pent tension, an odd mixture of grim seriousness and mocking exasperation at men's blindness, suggestive of a gargoyle.

"It was a hoax," he said coolly, "and I alone planned it. But it was a hoax that was absolutely necessary to prepare the world for that other invasion, against which I tried to warn you three days ago. The invasion whose vanguard is already in our midst. Of course Conjerly and Tempelmar testified against me—for they are part of the vanguard!"

"You're psychotic," said Shielding flatly, lowering his head a little, like a bull. "Paranoid. The only wonder is how it escaped the psychiatrists. Watch him, some of you"—he indicated those nearest Clawly—"while I call the attendants."

"Stay where you are, all of you! And you, Shielding, don't flip that beam!" Clawly had danced back a step, and a metal tube gleamed in his hand. "Since you believe I planned the Martian hoax—and I did—perhaps you'll believe that I won't stop at a few more deaths, not accidental this time, in order to make you see the truth. Idiots! Can't you see what's happening under your very noses? Don't you see what those reports may have meant? Call Co-ordination Center 1, Shielding. Go on, I mean it, call them!"

But at that instant Firemoor spun round in his chair and dove at Clawly, pinioning his arms, hurling them both down, wrenching the metal tube from his hand, sending it spinning to one side. A moment later he had dragged Clawly to his feet, still holding him pinioned.

"I'm sorry," he gasped miserably. "But I had to do it for your own sake. We were wrong—wrong to the point of being crazy. And now we've got to admit it. Looking back, I can't see how I ever—"

But Clawly did not even look at him. He stared grimly at Shielding.

"Thank you, Firemoor," said Shielding, a certain relief apparent in his voice. "You still have a great deal to answer for. That can't be minimized—but this last action of yours will certainly count in your favor."

This information did not seem to make Firemoor particularly happy. The pinioned Clawly continued to ignore him and to stare at Shielding.

"Call Communications Center 1," he said, deliberately.

Shielding dismissed the interruption with a glance. He sat down.

"The attendants will remove him shortly. Well, gentlemen," he said, "it's time we considered how best to repair the general dislocations caused by this panic. Also there's the matter of our position with regard to the trial of the accomplices." There was a general pulling-in of chairs.

"Call Communications Center 1," Clawly repeated.

Shielding did not even look up.

But someone else said, "Yes. I think now you'd better call them."

Shielding had started automatically to comply, before he realized just who it was that was speaking—and the particular tone that was being used.

It was Conjerly and the tone was one of command.

Conjerly and Tempelmar had risen, and were standing there as solidly as two obelisks—and indeed there was something unpleasantly monumental in their intensified, self-satisfied composure. Before anyone realized it, the center of attention of the meeting had shifted from Clawly and Firemoor to these new figures—or rather to these old and familiar figures suddenly seen in a new and formidable guise.

Shielding blinked at them a moment, as if he didn't know who they were. Then, with a haste that was almost that of fear, he swung around and flipped a beam on the board behind him.

Halfway up the terraced banks of gray squares, a panel came to life.

A man in black uniform looked down from it.

"Communications Center 1 seized for the Servants," he announced crisply in a queerly accented though perfectly intelligible voice.

Shielding stood stock-still for a moment, then flipped another beam.

"The soldiers of the Servants are in control at this point," said the second black-uniformed individual, speaking with equal crispness.

With a stifled, incredulous gasp, Shielding ran his hand down the board, flipping on all the panels in the Opal Cross sector.

Most of them showed black-uniformed figures. Of the remainder, the majority were empty.

And then it became apparent that not all the black-uniformed figures were merely televised images. Some of them were standing between the panels, in the Sky Room itself, holding weapons trained.

By a psychological illusion, the figures of Conjerly and Tempelmar seemed to grow taller.

"Yes," Conjerly said, soberly, almost kindly, "your government—or, rather, that absence of all sane control which you call a government—is now in the capable hands of the Servants of the People. Clawly's assertions were all quite correct, though fortunately we were able to keep you from believing them—a necessary deception. There is an invasion going on—an invasion that is in the best interests of all worlds, and one from which yours will benefit greatly. It is being made across time, through a region that has become common to both our worlds. That region is our transtime bridgehead. And, as is plain to see, our bridgehead coincides with your headquarters."

Clawly was not listening. He was watching a figure that was striding down the paneled terraces, its smilingly curious eyes fixed upon him. And as he watched, Firemoor and Shielding and some others began to watch too, slack-faced, dully amazed at this secondary impossibility.

The approaching figure was clad in black military flying togs whose sleek cut and suavely gleaming texture marked them as those of an individual of rank. But so far as physique and appearance were concerned, down to the last detail of facial structure, including even a similarity of expression—a certain latent sardonic mockery—he was Clawly's duplicate.

There was something very distinctive about the way the two eyed each other. No one could have said just when it started, but by the time they were facing each other across the control table, it was very plain; the look of two men come to fight a duel.

Clawly's face hardened. His gaze seemed to concentrate. His duplicate started, as if at a slight unexpected blow. For an instant he grinned unpleasantly, then his face grew likewise grim.

Neither moved. There was only that intense staring, accompanied by a silent straining of muscles and a breathing that grew heavy. But none of those who watched doubted but that an intangible duel was being fought.

Conjerly, frowning, stepped forward. But just then there grew a look of sudden desperate terror in the contorted face of Clawly's black-clad duplicate. He staggered back a step, as if to avoid falling into a pit. An unintelligible cry was wrenched out of him, and he snatched at his holster.

But even as he raised the weapon, there flashed across the first Clawly's features a triumphant, oddly departing smile.

In the black, cramping tunnel Thorn could only swing his knife in a narrow arc, and the snarl of the attacking dog was concentrated into a grating roar that hurt his eardrums. Nevertheless, knife took effect before fangs, and with an angry whimper the dog backed away—there was no room to turn.

From the receding scuffle of its claws Thorn could tell that it had retreated almost to the beginning of the tunnel. He relaxed from the crouch that had put his back against the rocky roof, sprawled in a position calculated to rest elbows and knees, and considered his situation.

Of course, as he could see now, it had been an inexcusable blunder to enter the tunnel without first building a fire to insure his being able to get back to a place from which he could use his slingshot. But coming down the ravine he hadn't seen a sign of the devils, and there was no denying it had been necessary to revisit the cave to see if Thorn III had any extra food, weapons, or clothing stored there. The need for food was imperative, and yesterday he and Darkington had completely failed in their hunting.

He wondered if Darkington would attempt a rescue. Hardly, since it would be late afternoon before the gnarled little man returned from his own hunting circuit. With night coming on, it was unlikely that he would risk his life venturing down into the ravine for the sake of a man whom he believed to be half-crazy. For Thorn had tried to tell him altogether too much about alternate worlds in which Civilization had not perished. Darkington had dismissed all this as "the dreams," and Thorn had shut up, but not until he realized he was forfeiting all Darkington's confidence in him as a hard-bitten and realistic neo-savage.

Besides, Darkington was a little crazy himself. Long years of solitary living had developed fixed habit patterns. His hunger for comradeship had become largely a subjective fantasy, and the unexpected appearance of an actual comrade seemed to make him uncomfortable and uneasy rather than anything else, since it demanded readaptation. A man marooned in a wilderness and trying to get back to civilization is one thing. But a man who knows that civilization is dead and that before him stretch only dark savage eons in which other creatures will have the center of the stage, is quite a different animal.

Something was digging into Thorn's side. Twisting his left hand back at an uncomfortable angle—his right still held the knife or cutter—he worked the pouch from under him and took out the offending article. It was the puzzling sphere that had stayed with him during all his passages between the worlds. Irritably he tossed it away. He had wasted enough time trying to figure out the significance or purpose of the thing. It was as useless as ... as that graveyard of skylons up there.

He heard it bound up the tunnel, roll back a way, come to rest.

Evidently his captors heard it too, for there came a sharp mewing and growling, which did not break off sharply, but sank into a confused palaver of similar sounds, strongly suggestive of some kind of speech. Once or twice he thought he recognized human words, oddly telescoped and slurred to fit feline and canine palates. It was not pleasant to be cramped up in a tunnel and wondering what cats and dogs were saying about you in a half-borrowed, quasi-intelligent jargon.

And then, very softly, Thorn thought he heard someone calling his name.

His almost immediate reaction was a sardonic grimace at the vast number of unlikely sounds a miserable man will twist into a resemblance of his name. But gradually the fancied sound began to exert a subtle pull on his thoughts, dragging them away toward speculations which his present predicament did not justify.

But who is to say what thoughts a trapped and doomed man shall think? As Thorn told himself with some calmness, this was probably his last stretch of reflective thinking. Of course, when death came sufficiently close, the fear of it might enable him to escape into another body. But that was by no means certain or even probable. He reflected that every exchange he had made had been into a worse world. And now, presumably, he was at the bottom, and like energy that has reached the nadir of its cycle of degradation, unable to rise except with outside help.

Besides, he did not like the idea of dooming any other Thorn to this predicament, although he was afraid he would do it if given the chance.

Again he dreamily fancied he heard his name called.

He wondered what was happening to those other Thorns, in their hodgepodged destinies. Thorn III in World II—had he died in the instant of his arrival there, or had the Servants noted the personality-change in time and perhaps spared him? Thorn II in World I. Thorn I in World III. It was like some crazy game—some game devised by a mad, cruel god.

And yet what was the whole universe, so far as it had been revealed to him, but a mad, cruel pageantry? The Dawn myth was right—there were serpents gnawing at every root of the cosmic ash Yggdrasil. In three days he had seen three worlds, and none of them were good. World III, wrecked by subtronic power, cold battlefield for a hopeless last stand. World II, warped by paternalistic tyranny, smoldering with hate and boredom. World I, a utopia in appearance, but lacking real stamina or inward worth, not better than the others—only luckier.

Three botched worlds.

He started. It was as if, with that last thought, something altogether outside his mind had attached itself to his mind in the most intimate way imaginable. He had the queerest feeling that his thoughts had gained power, that they were no longer locked-in and helpless except for their ability to control a puny lever-assembly of bones and contractile tissue, that they could reach out of his mind like tentacles and move things, that they had direct control of a vastly more competent engine.

A faint sound up the tunnel recalled his altered mind to his present predicament. It might have been a tiny scrape of claws on rock. It was not repeated. He gripped his knife. Perhaps one of the beasts was attempting a surprise attack. If only there were some light—

A yellowish flame, the color of the woodfire he had been visualizing, flared up without warning a few feet ahead, casting shafts of ruddy glare and shadow along the irregular tunnel. It lit up the muzzles of a gaunt gray dog and a scarred black cat that had been creeping toward him, side by side. For an instant surprise froze them. Then the dog backed off frantically, with a yelp of panic. The cat snarled menacingly and stared wildly at the flame, as if desperately trying to figure out its modus operandi .

But, with Thorn's thought, the flame advanced and the cat gave ground before it. At first it only backed, continuing to snarl and stare. Then it turned tail, and answering in a great screech the questioning mews and growls that had been coming down the tunnel, fled as if from death.

The flame continued to advance, changing color when Thorn thought of daylight. And as Thorn edged and squirmed along, it seemed to him that somehow his way was made easier.

The tunnel heightened, widened. He emerged in the outer chamber in time to hear a receding rattle of gravel.

The flame, white now, had come to rest in the middle of the rocky floor. Even as he stooped, it rose to meet him, winking out—and there rested lightly on his palm the gray sphere, cool and unsmirched, that he had tossed away a few minutes before.

But it was no longer a detached, external object. It was part of him, responsive to his every mood and thought, linked to his mind by tracts that were invisible but as real as the nerves connecting mind with muscle and sense organ. It was not a machine, telepathically controlled. It was a second body.

Relief, stark wonder, and exulting awareness of power made him weak. For a moment everything swam and darkened, but only for a moment—he seemed to suck limitless vitality from the thing.

He felt a surge of creativeness, so intense as to be painful, like a flame in the brain. He could do anything he wanted to, go anywhere he wanted to, make anything he wanted to, create life, change the world, destroy it if he so willed—

And then—fear. Fear that, since the thing obeyed his thoughts, it would also obey his foolish, ignorant, or destructive ones. People can't control their thoughts for very long. Even sane individuals often think of murder, of catastrophes, of suicide—

Suddenly the sphere had become a gray globe of menace.

And then—after all, he couldn't do anything . Besides any other limitations the thing might have, it was certainly limited by his thoughts. It couldn't do things he didn't really understand—like building a subtronic engine—

Or—

For the first time since he had emerged from the tunnel, he tried to think collectedly, with more than the surface of his mind.

He found that the depths of his mind were strangely altered. His subconscious was no longer an opaque and impenetrable screen. He could see through it, as through a shadowy corridor, sink into it, hear the thoughts on the other side, the thoughts of the other Thorns.

One of them, he realized, was instructing him, laying a duty upon him.

The message dealt with such matters as to make the imagination shiver. It seemed to engulf his personality, his consciousness.

His last glimpse of World III was a gray one of dark, snow-streaked pines wavering in a rocky frame. Then that had clouded over, vanished, and he was in a limitless blackness where none of the senses worked and where only thought—itself become a sense—had power.

It was an utterly alien darkness without real up or down, or this way or that, or any normal spatial properties. It seemed that every point was adjacent to every other point, and so infinity was everywhere, and all paths led everywhere, and only thought could impose order or differentiate. And the darkness was not that of lightlessness, but of thought itself—fluttering with ghostly visions, aflash with insight.

And then, without surprise or any consciousness of alteration, he realized that he was no longer one Thorn, but three. A Thorn who had lived three lives—and whether memory pictured them as having been lived simultaneously or in sequence seemed to matter not at all. A Thorn who had learned patience and endurance and self-sufficiency from harsh World III, who had had ground into the bedrock of his mind the knowledge that man is an animal in competition with other animals, that all human aspirations are but small and vaunting and doomed things—but not necessarily worthless therefore—in a blind and unfeeling cosmos, and that even death and the extinguishing of all racial hopes are ills that can be smiled at while you struggle against them. A Thorn who had seen and experienced in World II the worst of man's cruelty to man, who had gained a terrible familiarity with human nature's weaknesses, its cowardly submissiveness to social pressure, its capacity for self-delusion, its selfishness, its horrible adaptability, who had plumbed to their seething, poisoning depths the emotions of hate and resentment and envy and fear, but who in part had risen superior to all this and learned humility, and sympathy, and sacrifice, and devotion to a cause. A Thorn who, in too-easy World I, had learned how to use the dangerous gift of freedom, how to fight human nature's tendency to go evil and foul itself when it is not being disciplined by hardship and adversity, how to endure happiness and success without souring, how to create goals and purposes in an environment that does not supply them ready-made.

All these experiences were now those of one mind. They did not contradict or clash with each other. Between them there was no friction or envy or guilt. Each contributed a fund of understanding, carrying equal weight in the making of future decisions. And yet there was no sense of three minds bargaining together or talking together or even thinking together. There was only one Thorn, who, except for that period of childhood before the split took place, had lived three lives.

This composite Thorn, sustained by the talisman, poised in the dimensionless dark beyond space and time, felt that his personality had suddenly been immeasurably enriched and deepened, that heretofore he had been going around two-thirds blind and only now begun to appreciate the many-sidedness of life and the real significance of all that he had experienced.

And without hesitation or inward argument, without any sense of responding to the urgings of Thorn II, since there was no longer a separate Thorn II, he remembered what the death-resisting Oktav had whispered to him in the Blue Lorraine, syllable by agonized syllable, and he recalled the duty laid upon him by the seer.

He thought of the first step—the finding of the Probability Engine—and felt the answering surge of the talisman, and submitted to its guidance.

There was a dizzying sense of almost instantaneous passage over an infinite distance—and also a sense that there had been no movement at all, but only a becoming aware of something right at hand. And then—

The darkness pulsed and throbbed with power, a power that it seemed must rack to pieces many-branched time and shake down the worlds like rotten fruit. The thought-choked void quivered with a terrifying creativity, as if this were the growing-point of all reality.

Thorn became aware of seven minds crowded around the source of the pulsations and throbbing and quivering. Homely human minds like his own, but lacking even his own mind's tripled insight, narrower and more paternalistic than even the minds of World II's Servants of the People. Minds festooned with error, barnacled with bias, swollen with delusions of godhead. Minds altogether horrible in their power, and in their ignorance—which their power protected.

Then he became aware of vast pictures flaring up in the void in swift succession—visions shared by the seven minds and absorbing them to such a degree that they were unconscious of his presence.

Like river-borne wreckage after an eon-long jam has broken, the torrent of visions flowed past.

World II loomed up. First the drab Servants Hall, where eleven old men nodded in dour satisfaction as they assured themselves, by report and transtime televisor, that the invasion was proceeding on schedule. Then the picture broadened, to show great streams of subtronically mechanized soldiers and weapons moving in toward the transtime bridgehead of the Opal Cross. Individual faces flashed by—wry-lipped, uninterested, obedient, afraid.

For a moment World I was glimpsed—the interior of the Opal Cross shown in section like an ant-hill, aswarm with black uniforms. Quickly, as if the seven masters hated to look at their pet world so misused, this gave way to a panoramic vision of World III, in which hundreds of miles were swept over without showing anything but fallen or fire-tortured skylons, seared and scrub-grown wasteland, and—cheek by jowl—glacier walls and smoke-belching volcanoes.

But that was only the beginning. Fruits of earlier time-splits were shown. There was a world in which telepathic mutants fought with jealous nontelepaths, who had found a way of screening their thoughts. There was a world in which a scarlet-robed hierarchy administered a science-powered religion that held millions in Dawn Age servitude. A world in which a tiny clique of hypnotic telepaths broadcast thoughts which all men believed in and lived by, doubtfully, as if in a half-dream. A world where civilization, still atomic-powered, was split into tiny feudalistic domains, forever at war, and the memory of law and brotherhood and research kept alive only in a few poor and unarmored monasteries. A world similarly powered and even more divided, in which each family or friends-group was an economically self-sustaining microcosm, and civilization consisted only of the social intercourse and knowledge-exchange of these microcosms. A world where men lived in idle parasitism on the labor of submen they had artificially created—and another world in which the relationship was reversed and the submen lived on men.

A world where two great nations, absorbing all the rest, carried on an endless bitter war, unable to defeat or be defeated, forever spurred to new efforts by the fear that past sacrifices might have been in vain. A world that was absorbed in the conquest of space, and where the discontented turned their eyes upward toward the new frontier. A world in which a great new religion gripped men's thoughts, and strange ceremonies were performed on hilltops and in spacecraft and converts laughed at hate and misery and fear, and unbelievers wonderingly shook their heads. A world in which there were no cities and little obvious machinery, and simply clad men led unostentatious lives. A sparsely populated world of small cities, whose inhabitants had the grave smiling look of those who make a new start. A world that was only a second asteroid belt—a scattering of exploded rocky fragments ringing the sun.

"We've seen enough!"

Thorn sensed the trapped horror and the torturing sense of unadmitted guilt in Prim's thought.

The visions flickered out, giving way to the blackness of unactualized thought. On this blackness Prim's next thought showed fiercely, grimly, monstrously. It was obvious that the interval had restored his power-bolstered egotism.

"Our mistake is evident but capable of correction. Our thoughts—or the thoughts of some of us—did not make it sufficiently clear to the Probability Engine that absolute destruction rather than a mere veiling or blacking out, was intended, with regard to the botched worlds. There is no question as to our next step. Sekond?"

"Destroy! All of them, except the main trunk," instantly pulsed the answering thought.

"Ters?"

"Destroy!"

"Kart?"

"The invading world first. But all the others too. Swiftly!"

"Kant?"

"It might be well first to.... No! Destroy!"

With a fresh surge of horror and revulsion, Thorn realized that these minds were absolutely incapable of the slightest approach to unbiased reasoning. They were so fanatically convinced of the correctness of all their past decisions as to the undesirability of the alternate worlds, that they were even completely blind to the apparent success of some of those worlds—or to the fact that the destruction of a lifeless asteroid belt was a meaningless gesture. They could only see the other worlds as horrible deviations from the cherished main trunk. Their reactions were as unweighed and hysterical as those of a murderer, who taking a last look around after an hour spent in obliterating possible clues, sees his victim feebly stir.

Thorn gathered his will power for what he knew he must do.

"Sikst?"

"Yes, destroy!"

"Septem?"

"Destroy!"

"Okt—"

But even as Prim remembered that there no longer was an Oktav and joined with the others in thinking destruction, even as the darkness began to rack and heave with a new violence, Thorn sent out the call.

"Whoever you may be, wherever you may be, Oh you who created it, here is the Divider of Time, here is the Probability Engine!"

His thought deafened him, like a great shout. He had not realized the degree to which the others had been thinking in the equivalent of muted whispers.

Instantly Prim and the rest were around him, choking his thoughts, strangling his mind, thinking his destruction along with that of the worlds.

The throbbing of the darkness became that of a great storm, in which even the Probability Engine seemed on the verge of breaking from its moorings. Like a many-branched lightning-flash, came a vision of time-streams lashed and shaken—Worlds I and II torn apart—the invasion bridge snapped—

But through it Thorn kept sending the call. And he seemed to feel the eight talismans and the central engine take it up and echo it.

His mind began to suffocate. His consciousness to darken.

All reality seemed to tremble on the edge between being and not-being.

Then without warning, the storm was over and there was only a great quiet and a great silence present, that might have come from the end of eternity and might have been here always.

Awe froze their thoughts. They were like boys scuffling in a cathedral who look up and see the priest.

What they faced gave no sign of its identity. But they knew.

Then it began to think. Great broad thoughts of which they could only comprehend an edge or corner. But what they did comprehend was simple and clear.

Our quest for our Probability Engine and its talismans has occupied many major units even of our own time. We have prosecuted it with diligence, because we were aware of the dangers that might arise if the engine were misused. We built several similar engines to aid us in the search, but it turned out that the catastrophe in our cosmos which swept away the engine and cast one of the talismans up on your time-stream and planet, was of an unknown sort, making the route of the talisman an untraceably random one. We would have attempted a canvass of reality, except that a canvass of an infinitude of infinitudes is impossible. Now our quest is at an end.

I will not attempt to picture ourselves to you, except to state that we are one of the dominant mentalities in a civilized cosmos of a different curvature and energy-content than your own.

Regarding the Probability Engine—it was never intended to be used in the way in which you have used it. It is in essence a calculating machine, designed to forecast the results of any given act, weighing all factors. It is set outside space-time, in order that it may consider all the factors in space-time without itself becoming one of them. When we are faced with a multiple-choice problem, we feed each choice into the engine successively, note the results, and act accordingly. We use it to save mental labor on simple decision-making routines, and also for the most profound purposes, such as the determination of possible ultimate fates of our cosmos.

All this, understand, only involves forecasting—never the actualization of those forecasts.

But no machine is foolproof. Just because the Probability Engine was not made to create, does not mean that it cannot create, given sufficient mental tinkering. How shall I make it clear to you? I see from your minds that most of you are familiar with a type of wheeled vehicle, propelled by the internal combustion of gases, similar to vehicles used by some of the lower orders in our own cosmos. You would see in it only a means of transportation. But suppose one of your savages—someone possessing less knowledge than even yourselves—should come upon it. He might see it as a weapon—a ram, a source of lethal fumes, or an explosive mine. No safety devices you might install could ever absolutely prevent it from being used in that fashion.

You, discovering the Probability Engine, were in the same position as that hypothetical savage. Unfortunately, the engine was swept away from our cosmos with all its controls open—ready for tinkering. You poked and pried, used it, as I can see, in many ways, some close to the true one, some outlandishly improbable. Finally you worked off the guards that inhibit the engine's inherent creativity. You began to actualize alternate worlds.

In doing this, you completely reversed the function of the Probability Engine. We built it in order to avoid making unfavorable decisions. You used it to insure that unfavorable decisions would be made. You actualized worlds which for the most part would never have had a remote chance of existing, if you had left the decision up to the people inhabiting your world. Normally, even individuals of your caliber will show considerable shrewdness in weighing the consequences of their actions and in avoiding any choice that seems apt to result in unpleasant consequences. You, however, forced the unwise choices to be made as well as the wise ones—and you continued to do this after your own race had acquired more real wisdom than you yourselves possessed.

For the Probability Engine in no way increased your mental stature. Indeed, it had just the opposite effect, for it gave you powers which enabled you to escape the consequences of your bad judgments—and it truckled to your delusions by only showing you what you wanted to see. Understand, it is just a machine. A perfect servant—not an educator. And perfect servants are the worst educators. True, you could have used it to educate yourselves. But you preferred to play at being gods, under the guise of performing scientific experiments on a world that you didn't faintly understand. God-like, you presumed to judge and bless and damn. Finally, in trying to make good on your damnations, you came perilously close to destroying much more than you intended to—there might even have been unpleasant repercussions in our own cosmos.

And now, small things, what shall we do with you and your worlds? Obviously we cannot permit you to retain the Probability Engine or any of the powers that go with it or the talismans. Also, we cannot for a moment consider destroying any of the alternate worlds, with a view to simplification. That which has been given life must be allowed to use life, and that which has been faced with problems must be given an opportunity of solving them. If the time-splits were of more recent origin, we might consider healing them; but deviation has proceeded so far that that is out of the question.

We might stay here and supervise your worlds, delivering judgments, preventing destructive conflicts, and gradually lifting you to a higher mental and spiritual level. But we do not relish playing god. All our experiences in that direction have been unpleasant, making us conclude that, just as with an individual, no species can achieve a full and satisfactory maturity except by its own efforts.

Again, we might remain here and perform various experiments, using the set-ups which you have created. But that would be abhorrent.

So, small things, there being no better alternative, we will take away our engine, leaving the situation you have created to develop as it will—with transtime invasions and interworld wars no longer an immediate prospect, though looming as a strong future possibility. With such sufferings and miseries and misunderstandings as exist, but with the future wide open and no unnatural constraints put on individuals sufficiently clear-headed and strong-willed to seek to avoid unpleasant consequences. And with the promise of rich and unusual developments lying ahead, since, so far as we know, your many-branched time-stream is unique among the cosmoses. We will watch your future with interest, hoping some day to welcome you into the commonwealth of mature beings.

You may say that we are at fault for allowing the Probability Engine to fall into your hands—and indeed, we shall make even stronger efforts to safeguard it from accident or tinkering in the future. But remember this. Young and primitive as you are, you are not children, but responsible and awakened beings, holding in your hands the key to your future, and with only yourselves to blame if you wantonly go astray.

As for you individuals who are responsible for all this botchwork, I sympathize with your ignorance and am willing to admit that your intentions were in part good. But you chose to play at being gods, and even ignorant and well-intentioned gods must suffer the consequences of their creations. And that shall be your fate.

With regard to you, Thorn, your case is of course very different. You responded to our blindly broadcast influencings, stole a talisman, and finally summoned us in time to prevent catastrophe. We are grateful. But there is no reward we can give you. To remove you from your environment to ours would be a meaningless gesture, and one which you would regret in the end. We cannot permit you to retain any talismanic powers, for in the long run you would be no better able to use them wisely than these others. We would like to continue your satisfying state of triplicated personality—it presents many interesting features—but even that may not be, since you have three destinies to fulfill in three worlds. However, a certain compromise solution, retaining some of the best features of the triplication, is possible.

And so, small things, we leave you.

From hastily chosen places of concealment and half-scooped fox-holes around the Opal Cross, a little improvised army stood up. A few scattered fliers swooped down and silently joined them. The only uniforms were those of a few members of the Extraterrestrial Service. Among the civilians were perhaps a score of Recalcitrant Infiltrants from World II, won over to last-minute co-operation by Thorn II.

The air still reeked acridly. White smoke and fumes came from a dozen areas where earth and vegetation had been blasted by subtronic weapons. And there were those who did not stand up, whose bodies lay charred or had vanished in disintegration.

The ground between them and the Opal Cross was still freshly scored by the tracks of great vehicles. There were still wide swathes of crushed vegetation. At one point a group of low buildings had been mashed flat. And it seemed that the air above still shook with the aftermath of the passage of mighty warcraft.

But of the great mechanized army that had been fanning out toward and above them, not one black-uniformed soldier remained.

They continued to stare.

In the Sky Room of the Opal Cross, the members of the World Executive Committee looked around at a similar emptiness. Only the tatters of Clawly's body remained as concrete evidence of what had happened. It was blown almost in two, but the face was untouched. This no longer showed the triumphant smile which had been apparent a moment before death. Instead, there was a look of horrified surprise.

Clawly's duplicate had vanished with the other black-uniformed figures.

The first to recover a little from the frozenness of shock was Shielding. He turned toward Conjerly and Tempelmar.

But the expression on the faces of those two was no longer that of conquerors, even thwarted and trapped conquerors. Instead there was a dawning, dazed amazement, and a long-missed familiarity that told Shielding that the masquerading minds were gone and the old Conjerly and Tempelmar returned.

Firemoor began to laugh hysterically.

Shielding sat down.

At the World II end of the broken transtime bridgehead, where moments before the Opal Cross had risen, now yawned a vast smoking pit, half-filled with an indescribable wreckage of war machines and men, into which others were still falling from the vanished skylon—like some vision of Hell. To one side, huge even in comparison with that pit, loomed the fantastically twisted metal of the transtime machine. Ear-splitting sounds still echoed. Hurricane gusts still blew.

Above it all, like an escaping black hawk above an erupting volcano, Clawly flew. Not even the titanic confusion around him, nor the shock of the time-streams' split, nor his horror at his own predicament, could restrain his ironic mirth at the thought of how that other Clawly, in trying to kill him, had insured the change of minds and his own death.

Now he was forever marooned on World II, in Clawly II's body. But the memory chambers of Clawly II's brain were open to him, since Clawly II's mind no longer existed to keep them closed, and so at one bound he had become a half-inhabitant of World II. He knew where he stood. He knew what he must do. He had no time for regrets.

A few minutes' flying brought him to the Opal Cross and it was not long before he was admitted to the Servants Hall. There eleven shaken old men looked up vengefully at him from reports of disaster. Their chairman's puckered lips writhed as he accused: "Clawly, I have warned you before that your lack of care and caution would be your finish. We hold you to a considerable degree responsible for this calamity. It is possible that your inexcusably lax handling of the prisoner Thorn was what permitted word of our invasion to slip through to the enemy. We have decided to eliminate you." He paused, then added, a little haltingly, "Before sentence is carried out, however, do you have anything to say in extenuation of your actions?"

Clawly almost laughed. He knew this scene—from myth. The Dawn Gods blaming Loki for their failures, trying to frighten him—in hopes that he would think up a way to get them out of their predicament. The Servants were bluffing. They weren't even looking for a scapegoat. They were looking for help.

This was his world, he realized. The dangerous, treacherous world of which he had always dreamed. The world for which his character had been shaped. The world in which he could play the traitor's role as secret ally of the Recalcitrants in the Servants' camp, and prevent or wreck future invasions of World I. The world in which his fingers could twitch the cords of destiny.

Confidently, a gargoyle's smile upon his lips, he stepped forward to answer the Servants.

Briefly Thorn lingered in the extra-cosmic dark, before his tripled personality and consciousness should again be split. He knew that the True Owners of the Probability Engine had granted him this respite in order that he would be able to hit upon the best solution of his problem. And he had found that solution.

Henceforward, the three Thorns would exchange bodies at intervals, thus distributing the fortunes and misfortunes of their lives. It was the strangest of existences to look forward to—for each, a week of the freedoms and pleasures of World I, a week of the tyrannies and hates of World II, a week of the hardships and dangers of World III.

Difficulties might arise. Now, being one, the Thorns agreed. Separate, they might rebel and try to hog good fortune. But each of them would have the memory of this moment and its pledge.

The strangest of existences, he thought again, hazily, as he felt his mind beginning to dissolve, felt a three-way tug. But was it really stranger than any life? One week in heaven—one week in hell—one week in a frosty ghost-world—

And in seven different worlds of shockingly different cultures, seven men clad in the awkward and antique garments of the Late Middle Dawn Civilization, began to look around, in horror and dismay, at the consequences of their creations.

THE END.