As the ship rose on its column of fire some of the old love of distance and enigma came back to Ed. There was also a sense of adventurous escape, like that of city workers of centuries ago, when, chucking business and office routines, they had rushed to the country on weekends to regain a little of primitive nature while they scorched a steak over a smoky fire in the woods.

On the Moon Dust there were more women and children than men: refugees from danger. But would old Mars be much safer? Didn't it now belong to the same human civilization, with its dark undercurrents?

The Dukases were smoothly hurled across the vast trajectory to Mars. They landed at a high south-temperate latitude, not far below the farthest extent limit of the polar cap; though now, in summer, it had dwindled to a mere cake of deep hoarfrost a few hundred miles across and on high ground. Around this remnant stretched a yellow plain made up of crusting mud, swiftly drying lakes scummed with the Martian equivalent of green algae, and white patches of ancient-sea salt and alkali.

But Port Smitty itself was in a wide, shallow valley, or "canal," a bit farther north. Its many airdomes, necessary to maintain an atmosphere dense enough and sufficiently oxygenated to sustain human life, loomed among vast greenhouses and thickets of tattered, dry-leaved plants. The central dome was topped by a statue of old Porter Smith, this region's first human inhabitant; he was still alive but long gone from the Mars he had loved. For he had associated himself with the building of star ships.

Port Smitty already boasted a population of half a million. And there were other cities of almost equal size. On Mars, many of the first rejuvenated had settled. And many colonists of every sort had come there since.

On the rusty bluff overlooking the city were the remains of a far older metropolis—towers, domes and strange nameless structures for which anything manlike could have no use. Fifty million years ago the Martians, like the people of the Asteroid Planet, had been wiped out in war.

Ed Dukas and his bride rode by tube train from the flame-blasted spaceport to the city. Their hotel room overlooked a courtyard lush with earthly palms and flowers. Birds twittered and flitted from branch to poppy bloom. From somewhere in the hotel came dance music.

Their room was supposed to be energy-shielded, but Ed remained cautious. He merely left his penpoint bared in his coat pocket, with the envelope of an old letter. He had already told Barbara all he knew about Uncle Mitch's message and had added some wild guesses. So now she gave her husband a smile of understanding as he hung his coat carefully on a chair. Then she came into his arms.

Later that evening, dancing, they covered their wariness carefully. They might be under observation in any of a hundred different ways: by probe beams, hidden cameras, or by individuals, android or human, whom they did not know. In spite of old loyalty, Ed Dukas was not entirely at ease with the thought of contacting Mitchell Prell. Yet, he wished to avoid being trailed so that he could act alone and separate from the dictatorial and often panic-stricken opinions of others.

On Mars there had been considerable violence, too, though there had been no gliding, sinuous things that brought nocturnal terror. But here, too, there was a mingling of android and human being, with no visible marks to distinguish the one from the other, though to many the difference was as great as that between man and werewolf.

Barbara seemed to grow sleepy in Ed's arms as they danced. Ed yawned slightly. So they drifted from the room and back to their own quarters.

Ed pulled the old envelope from the pocket of the coat on the chair. As he had hoped, a message was traced waveringly on it: "Go Port Karnak—then E.S.E. into desert."

Both Ed and his wife knew that Martian deserts surpassed all earthly conceptions of desolation. They looked at each other. The challenge was still in Barbara's eyes. The fact that she could carry a pack was a matter that had been settled long ago.

Now Ed risked speaking—in the lowest of audible whispers: "So, instead of going to bed, as people in our position should, we start traveling—fast."

He felt the safety pouch under his belt. Personal recordings were in it: tiny cylinders, a pair for each of them. A precaution. In the vaults on Earth there should still be others. But one could not always be sure of those. Some had disappeared.

As memory of what he thought he had seen in a tiny ink drop still clutched rather frighteningly at Ed Dukas's brain. It was a hint of how Mitchell Prell wrote his messages—in an utterly simple and heroic way, but with fantastic, dream-shot implications. Could it be part of android flexibility? Well, probably his fancy had tricked him, because things couldn't be that odd. Still....

Often Ed had felt bitter over the confusions created by the advance of science. But now enigmas led him on as thrillingly as ever. There had to be wonders ahead, for thinking of Mitchell Prell without thinking of new science was impossible.

"Let's go, Babs," he whispered.

Casually, like ordinary guests checking out, they put two light valises into the conveyer and dropped to the main floor by elevator. The rest of their stuff they left behind. They paid their bill and took an auto cab to the central tube station. In the washrooms they changed from leisure clothes to the rough gear used in the Martian wilderness: light-weight vacuum armor and oxygen helmets equipped with air purifiers and small radios—all fitted over light trousers and shirts. The remaining contents of their discarded valises they transferred to rucksacks.

In the station they mingled with farmers, miners and homesteaders. Couples such as themselves were common on Mars; they were going out to make their fortunes.

They bought their tickets to Port Karnak. Ed and Barbara looked around them. A half-dozen men among the waiting passengers wore no oxygen helmets. True, this underground depot was pressurized, but the outer thinness and oxygen-poverty of the Martian air had to be prepared for. The absence of helmets, then, almost had to be the mark of the android. To keep its vital processes going, the versatile vigor of vitaplasm merely disintegrated a tiny bit of its atomic substance, to make up for the shortage of chemical energy.

Ed and Barbara boarded the train with the crowd. Much of this underground system of transportation had merely been converted to human beings' use from that which had remained from the ancient culture of Mars. Behind the projectilelike coaches, close fitting in the tubes, air-pressure built up. Acceleration was swift. Covering the thousand-mile distance to Port Karnak took twenty minutes.

Once arrived, Ed bought the additional equipment they needed; then in a small restaurant they ate a last civilized meal. They took an auto bus out along a glassed-in, pressurized causeway and descended at the final stop, beside a few scattered greenhouses, the outermost of which provided the city with fresh, earthly vegetables.

Here the desert was at hand, utterly frigid at night, under the splinters of stars. Deimos, the farther moon, hung almost stationary in the north. Irregular in shape, it looked like a speck of broken chinaware, just big enough to make its form discernible. Probably it was a small asteroid which the gravity of Mars had captured.

The Dukases began to plod. The desert came under their boots, and the solidity of the ground gave way, gradually, to a difficult fluffiness, like that of dry flour. It was millions of square miles of dust the color of rusted iron, which, in part, it was. Dust, ground to ultimate fineness by eons of thin, swift wind. Under the dim light of the sky, colors dropped in tone to a monotonous grayness that only faintly revealed the nearest dunes, and showed plumes of soil moving on the wind like ghosts. The dust made a constant, sleepy soughing against their helmets, like an invitation to death.

Barbara pressed Ed's gloved hand, as if in reassurance, and he pressed hers in return. Maybe they had eluded all pursuit or probe-beam tracking. Certainly the blowing dust itself would be an effective screen against the most refined radar device. Yet to vanish from the view of men could mean another kind of danger. It came to Ed that even when Mars had teemed with millions of its own inhabitants, perhaps no one had trod within a mile of where he and his wife were now walking.

The Dukases marched on for an hour without saying anything. But during a momentary rest Barbara gripped Ed's arm, thus establishing a firm sonic channel, so that they could talk without using their helmet radios, which might betray them.

"I hope we're not too crazy, Ed," she said. "Going out into a wilderness like this, on the basis of a couple of strange notes, and with blind faith that somehow we'll be guided. I hope; I hope!"

Her tone was light and courageous, and he was more than ever glad.

"Think of our muddled home world, and make that a prayer," Ed said. "We might be doing something to help."

So they kept up their march through the night and into the weirdly beautiful dawn. The desert was rusty dun. The sky was deep, hard blue. The dunes were dust-plumed waves, in which a footprint was quickly lost. The rocks were wind-carven spires. Earth was the bluish morning star. It looked very peaceful, denying the need for haste. Its ring was a nebulous blur.

Barbara and Ed sucked water into their mouths through the tubes which led back from their helmets to the large canteens in their rucksacks. They swallowed anti-fatigue and food tablets. For a moment they even removed their oxygen helmets. There was no great harm in that; only the distention of blood vessels under swiftly lowered air pressure and an ache and ringing of eardrums, and of course the stinging dryness of the Martian cold against their cheeks. Forty-eight degrees Fahrenheit, below zero, it was just then.

"No more clowning," Ed said as they replaced their helmets. "We might get dazed by oxygen starvation and forget what we're doing."

They kept up their march, through the morning, past the almost warm Martian noon, and on into the frosty chill that came long before sunset. They were still plodding on when it was dawn once more. In spite of anti-fatigue capsules, they were getting pretty groggy.

In his breast pouch Ed had his pen and the envelope on which the latest message from Mitchell Prell had been inked. Now, surely, there had been time enough. So he ventured to disturb the writing materials. There were more words on the envelope: "True on course—keep moving."

So they continued to follow the pointer of their small gyrocompass, set to stab precisely toward east-southeast. Ed no longer questioned an odd miracle. It was simply there, and he was grateful.

An hour later Barbara glimpsed fluttering movement near by: a fleck of bright yellow. Then it was gone behind a large chip of stone. Then it appeared again. Ed saw it, too, for an instant. It fluttered, it chirped plaintively. It was an impossibility in the wastelands of Mars, or anywhere else on the Red Planet, outside of an air-conditioned cage. It was a small, earthly bird. A canary.

Barbara stared at it. Her blue eyes were bloodshot and scared. The tired droop of her cheeks deepened.

"Darling," she said rather lamely. "I think that fatigue is about to get the better of us."

"Think again," Ed said.

"I guess you're right," she answered. "Even without vitaplasm, it's not much of a stunt to give a guided missile or a spy-robot the form of a little bird, with television eyes. And a Midas Touch weapon, or something equally unpleasant, built into it. At the hotel in Port Smitty, it was unrecognizable among the other caged canaries. Here, though, it's unmistakably identified. Which means that whoever is guiding it—the police looking for your Uncle Mitch or friends of Granger's, or whoever else—don't care any more that we know what it is. We're helpless now—they think."

A dull fury came to Ed Dukas. He might have guessed that all chances of their eluding surveillance would have been countered carefully. This birdlike mechanism must have followed them all the way from Port Smitty, keeping just out of sight.

Then a more hopeful idea hit him. But reason conquered it. "No," he said aloud, gripping Barbara's shoulder so that she could hear. "If the pseudo-canary was Uncle Mitch's guide for us, it would have revealed itself sooner, and the messages on paper would not have been necessary."

In a flash Ed drew his own Midas Touch and fired it at the place among the broken rocks where the canary had just vanished. At a little distance there was the usual spurt of incandescence, fringed now with red dust. But from the projecting boulders near its base, a small yellow form spurted with a faint and musical twitter of mockery. Then a heavy voice spoke—one which neither Ed nor Barbara recognized just then:

"Better luck next time, robot lovers. Lead on!"

Thereafter, the false canary was careful not to show itself. And Ed was left with his frustrated anger, and with other uncertain thoughts. What if the written messages had not come from Mitchell Prell at all, but from someone else with an unknown purpose? Or, what if they were from Uncle Mitch, but had been prepared long ago and left to be presented to him, Ed Dukas, by means of some mechanical agent? What if—well—many things.

Using his tiny portable radar unit to locate the bird drew only a blank. Perhaps the little mechanism with a radio speaker for a voice was effectively shielded against such detection, even at short range.

To attempt evasive action would be a waste of time and waning energy. There was nothing to do but go on, see what developed, and trust to luck. There was the certainty that real pursuit would come, but what shape it would take remained unknown.

As Ed and Barbara plodded on through the day, their minds became fuzzy with weariness. Once, in a kind of retreat from present harsh facts, Ed's thoughts touched a vivid daydream that he'd had before, of a planet of some star. He looked down at imaginary dry ground under imaginary feet and saw that each pebble under the strange, brilliant sunshine had a little hole in it. And something shaped like a cross, with four rough, brownish-gray arms that could bend in any direction, scrabbled away, flat against the soil, its equipment glinting. The thickets all around were stranger than those of Mars.

Yes, it was just a daydream, originating from within himself, like an old, half-buried hope of some distant exploration. He wondered if it could ever still have any fulfillment, or if that even mattered any more? Perhaps, for all he knew, his wife and he were now headed for an even stranger region.

Ed shook his head to clear it. He did not want to disturb the envelope in his pouch too often. To expose the ink to the dried-out Martian air, while the writing was in progress at hour-hand speed, might spoil a vital message. But at last he chanced it. It seemed that the writer was not much troubled by the presence of the bird-thing or what it might mean.

Barbara and Ed read avidly: "Base of capped granite rock before you. Lab."

Barbara nodded toward a formation which loomed a half mile ahead in the freezing cold of late afternoon. The slab, balanced crosswise on a slender pinnacle, identified it beyond doubt, though there were other similar spires around it. It cast its shadow on the sunlit dunes. Or was all of that dark, irregular patch shadow?

Ed Dukas and his bride had not enjoyed the luxury of natural sleep for a long time. But summoning their flagging strength, they hurried forward. Ed felt that at last he was approaching the solution of ten-year-old enigmas.

The darker area at one side of the capped rock was not all shadow. But the Dukases had scant attention for the bluish masses of plushy stuff that grew in this aridity. At another time it might have been fascinating, for it was vegetation related to the android as moss is related to a man. It was a growth of vitaplasm—another of Mitchell Prell's experiments. But Ed and Barbara had no chance to ponder this.

They located an eighteen-inch cleft at the rock's base. Edging into it, they found an irregular stone pivoted on steel hinges. To their touch, it closed behind them, and bolts clicked. From the outside now the outline of the door would seem merely a pattern of natural cracks in the granite pinnacle.

Atomic battery lamps lighted the passage, and there were more heavy doors, some of them of steel, for Ed and Barbara to bolt behind them. The place was like a small, secret fortress. At the bottom of a spiral stair, beyond a small airlock, was Mitchell Prell's latest and perhaps last workshop.

He must have blasted it from the crust of Mars without help. It was a series of a half-dozen rooms and was no larger than a fair-sized apartment. Smallest of all was the combined sleeping room and kitchen; and there the evidence of months or perhaps years of absence was plainest. The bunk was thick with dust, and food remnants were blackened on unwashed plates. The air, of earthy density, smelled of decay and a strange pungence. The floors and walls were crusted with patches of the tough, bluish growths seen outside. It was suggestive at once of both fungus and moss but was really like neither. It had a pretty color under the lamps, which had certainly been burning for a long time.

Ed and Barbara removed their oxygen helmets and began a swift exploration of the premises. The rooms had all the marks of lone bachelor occupancy by a man too fearfully busy with his own deep pursuits to waste time on more than the barest attempts at housekeeping. Apparatus was everywhere. There were even recognizable parts of a helicopter—the one, no doubt, which had brought Prell and his equipment to this refuge.

At first they thought that he might since have fallen victim to some violence or accident. And then they found his body in a rectangular, plastic-covered tank, submerged in a cloudy, viscous fluid. It was a standard sort of vat, much used in laboratories in repairing extensive injury and restoring a destroyed body from a personal recording—either in protoplasm or vitaplasm. Near by, there were three similar vats, which, when opened, proved to contain only fluid.

Barbara and Ed looked for a long moment at Mitchell Prell's forever young face. It was peaceful in death that was not quite death; for of the latter you could never be sure any longer, unless it was the death of the species.

If there were guile behind that gentle face, it did not show. If there were darkness of purpose, or stubborn unwillingness to recognize errors that he had committed in a civilization that tottered as it reached for greatness, it could not be seen. But in this refuge, one fact was plain: Mitchell Prell had gone on with his work in a super-biology.

Ed wandered over to a beautiful microscope of a standard make. Its attachments also started out from a familiar design. It was fitted with dozens of special screws and levers. When Ed, and then Barbara, peered into its eye-piece, they found that each of these screws and levers could manipulate a tiny tool, almost too small to see with the naked eye. There were minute cutters, calipers and burnishing wheels. Set up under the microscope there was even what seemed to be a tiny lathe. In fact, there was an entire machine shop on an ultra-miniature scale. And there were tiny, tonglike grasping members, intended to serve—on such a reduced scheme of things—as hands, where the human hand, working directly, would have been hopelessly mountainous.

In addition to this equipment, there were exact duplicates of the vats across the room and their attendant apparatus, except that each entire assembly was less than a half-inch long. In one vat there was a human figure much smaller than a doll, yet perfect.

Barbara laughed nervously. Even in this century of wonders, the human mind had its limitations for making swift adjustments. The laugh was a denial of what her eyes beheld.

Ed Dukas's wide face looked at once avid and haggard. Beside the tiny vats there was also another microscope, complete in every detail, yet of the same relative dimensions as the little figure in the vat. But this lesser microscope was of the electron variety. It had to be. For at this reduced size light waves themselves were too coarse in texture to be effective for close-range work.

Ed turned slowly toward his young wife, whose eyes were alert and wonder-filled in spite of her weariness. He noticed the pleasant wave in her hair. He noted the charming curve of her brow, the tiny and pleasing irregularity of her nose. And what was all this attention but a clinging to an object of love when facing a strangeness so great that it scared him as he had never been scared before. Ed Dukas knew that his face must have gone gray.

Now his words came slowly and precisely: "Babs, I've told you that I watched part of Mitchell Prell's first message being written. That in the moving speck of wet ink, for an instant something looked like a man the size of a mote! I thought I'd imagined it. But is that what Uncle Mitch is now? An android so small that the only way for him to write a note to a person of usual dimensions is to surround his own body with a droplet of ink and to drag himself across the paper, making the lines and loops of script?"

Barbara looked at him obliquely, doubting his seriousness.

"Aw, now, Eddie-boy, take it a little bit easy," she said. "Please do."

He didn't answer her. He let his unchanging expression and many seconds of silence do the answering for him. His pulses drummed in his ears.

At last he said, "No, darling, I mean it. There's no reason why an android no bigger than the smallest insects can't exist. And the signs of what Mitchell Prell did in this laboratory are plain enough.

"Working at first with the larger microscope and the miniature tools and machinery under it, he duplicated a now common kind of biological apparatus in half-inch size. In its tank he caused to grow the simulacrum of himself that you can see. Aside from the difference in dimensions, that much has been both possible and fairly common practice for years. Its brain having been stamped with all phases of his memory and personality, it became him when it awoke. His own body he left inert and preserved in the large vat. But he was not finished. He had made just one step toward the degree of smallness that he wanted to reach. So he started over from scratch, constructing first another microscope and then relatively minute machinery and tools, fine beyond our sight. Under that tiny electron microscope I'll bet there's another, smaller machine shop, and a smaller tank from which a mote-sized Mitchell Prell emerged. It must all have been quite a job. It's not hard to see where those ten years went."

Barbara was silent for a long time. Finally, she said, "It sounds reasonable—superficially. But still, is it possible? Consider a brain. It can come in many sizes, from an ant's to a human being's. But all are made of molecules of the same dimensions. And it has been pretty well determined that a brain must be always about as big as a human being's to be truly intelligent. Trying to cram such intelligence into a smaller lump of gray matter—composed of the familiar molecules—would be like trying to weave fine cloth out of rope. How can you get around that, Ed?"

"Maybe I can guess," he said. "With smaller units. How about the electron, Babs? Far smaller than the molecule, certainly. And it's been the soul of the best calculators—thought machines—for a couple of centuries. There isn't any doubt that a brain of microscopic size could function by far finer electronic patterning. No, it probably wouldn't work in natural protoplasm. But we already know the flexibility of vitaplasm: easy to redesign, capable of drawing its energy even from a nuclear source. Well, you figure it out. What have we here but other android advantages? I think my uncle once told me that he meant to go where no one could go exactly as a human being."

"All right, Eddie," she conceded. "I guess I'm persuaded. Proud girl, me. I've got a smart boyfriend. And your uncle—he skips blithely from the bigness of the interstellar regions in his thoughts to the smallness of dust! And he seems, actually, to have done the latter—in person! Is that what we're supposed to accept as truth? If so, he must have been with you all the time, or at least for quite a while. On Earth, even. And he must have come out to Mars with us. He was right in your pocket, riding with the paper and pen. To write, he must have gunked himself up good with the ink inside the pen point. Ugh—what a thought! And maybe he's still in your pocket right now. He—or a tremendously shrunken equivalent of him. Does all this stack up right in your eyes, Ed?" A pallor had crept through Barbara's tan.

"Pretty much so," Ed replied heavily.

"So what do we do now, Ed? Try to follow your uncle's path—down?"

Ed's flesh tingled. To follow Mitchell Prell down—a course more weirdly remote than traveling to the stars. He did not answer Barbara. He unzipped his pocket. He could not tell whether a minute android emerged or not. There were no further messages on the envelope.

But from a sound cone in a shadowy corner of this workshop, there suddenly came tones that a decade had not rubbed from his memory:

"Nipper-hello! Or is it always Ed now? So we've come to Mars together. And you with Barbara! Well, maybe that is an agreeable complication! Now we can talk. Here I have the right amplifying apparatus. I need help, and you always seemed the best—and enough like me. I know your doubts about science, and I don't blame you. But I'm still the same—wanting to learn everything that I can, feeling that everything should work out right."

The stillness closed in again. Ed and Barbara looked at each other. Technology was full of tricks—the possibility of a thousand illusions. Could he even trust a voice, made so like Mitchell Prell's used to be? And could he trust the mind behind it? Even if it truly was his uncle's?

"Work out right!" Ed growled mockingly. "That sounds almost pious! If you are what you say you are, you were on Earth and have seen everything. You know then how right things have been! I was around when the Moon blew—remember? And no scared hotheads caused that. But there are plenty of them now. And from here on Mars, I've expected to see Earth momentarily puff up into a little nova."

There was a sigh from the sound cone. "So I'm to blame—at least partly—for helping to give those fools something to be furiously right or mistaken about," Mitchell Prell's voice replied. "Well, I was what I was, and I am what I am, Ed. I'm sorry about many things that happened. But I can't erase them. I've urged you to come here to help me try to counteract them. I don't think you'll stay angry with me, Ed. Come where I am—you and Barbara. It can be done quite quickly now. I have two forms prepared. They will take the lines and personalities of anyone. Just set the dials above two of the unoccupied vats at one hundred—full energy. Lower yourselves into the fluid. Clothes, or lack of them, won't matter. Your own bodies will sink into suspended animation."

Again the voice from the sound cone faded out. Ed's and Barbara's eyes met in a tense congress of thought. They were being asked to leave their natural, physical selves behind and to become beings of vitaplasm. To many, that was horror in itself, even without a radical change in size. Then there was the fear of loss of identity. To be an exact duplicate in mind and memory might not necessarily mean to be the same person. Here was a metaphysical problem elusive and hard to answer. What others of experience might have told you could never quite satisfy you. You had to learn for yourself.

Beyond all that, there was that drop, down and down into tininess, to where physical laws themselves must seem warped by the relativity of size levels, and to where nothing remained quite the same. Could one's mind even endure the difference?

For a moment Ed felt cornered and panicky. But something eager and questioning came into him. For the first time he wished that Barbara had not come with him.

Finally he said, "I've got to go down, Babs. There just isn't any other way."

"What's sauce for the gander is sauce for the goose, Ed," she said. "With us, that was settled a while ago."

He didn't protest. She was resourceful. She'd be a help, not a trouble. And he knew that love of adventure was as strong in her as in himself. So the decision was made.

Suddenly they heard a distant clink and hammering. Metal against stone. The canary had followed them to Mitchell Prell's underground fortress. And of course the little mechanism had been merely a scout for some larger party farther to the rear.

Again the words came from the sound cone, but in a whisper, "I was pretty sure you'd be followed, Ed. But we should still have considerable time. It'll be hard for them to break into here—without destroying everything. And I think they'll want to see what I've got."

Ed Dukas had never before considered his brilliant tireless uncle in any way impractical. But now he was sensing a certain inadequacy and felt that Mitchell Prell truly needed him. If it was Mitchell Prell, of course—if the voice itself wasn't a trick. But now Ed was at least more confident that he was not being fooled. What doubt remained had to be part of many calculated risks.

"All right, Uncle Mitch," he said.

Barbara smiled at him rather wanly, but her eyes held a glint. He kissed her.

"So here goes, eh, Eddie?" she said.

"Be seein' yuh, sweetheart," he said, taking her in his arms.

---