"I'm a good organizer," Fenton said carefully. "I know how to handle people. I've got fast reflexes and dependable judgment. You toughened me. You gave me some bad years. You arranged for me to kill a few people—in line of duty, naturally—and I've done your dirty jobs until I know all the ropes. I can take care of myself."

  "Only as long as I let you," Torren told him with a faintly ominous ring in the deep voice. "Maybe it was a whim that made me pick you out of the asylum. But I've invested too much in you, Ben, to let you walk out on me now. What you need is work-hardening, my boy." He cupped water in his hand and let it drain out. "Who was it," he inquired, "that said no man is an island? You're looking at an island, Ben. I'm an island. A floating island. No one alive has any claim on me. Not even you. Don't try me too far, Ben."

  "Have you ever thought I might kill you some time, Torren?" Fenton asked gently.

  The colossus in the tank laughed heavily.

  "I ran a risk, making you my heir," he admitted. "But you won't kill me to inherit. I made sure. I tried you. You were given chances, you know ... no, I don't think you did know. I hardened you and toughened you and gave you some bad years, and some men might want to kill me for that. But not you. You don't hate me, Ben. And you're not afraid of me. Maybe you ought to be. Ever think of that, Ben?"

  Fenton turned and walked toward the door. Between two pillars he paused and glanced back.

  "I nearly killed you thirteen years ago," he said.

  Torren slapped his palm downward, sending a splash of liquid high.

  "You nearly killed me!" he said with sudden, furious scorn. "Do you think I'm afraid of death? When I wasn't afraid to live? Ben, come back here."

  Fenton gave him a level look and said, "No."

  "Ben, that's an order."

  Fenton said, "Sorry."

  "Ben, if you walk out of this room now you'll never come back. Alive or dead, Ben, you'll never come back."

  Fenton turned his back and went out, through the anteroom and the great steel doors that opened at his coming.

  -

  Stooping above the open suitcase on his bed, both hands full, Fenton saw the slightest possible shadow stirring in reflection on the window before him and knew he was not alone in the room. No buzzer had warned him, though the full spy-beam system was on and it should have been impossible for anyone to pass unheralded.

  He lifted his head slowly. Beyond the broad window the snowy hills of Ganymede lay undulating to the steep horizon. The clouds that blanketed the world were blue-tinged with Jupiter-light, reflecting from Jupiter's vast bright-blue seas of liquid ammonia. Between two hilltops he could see one of the planting-valleys veiled in mist, dull turquoise warm by contrast with the snow. The reflection swam between him and the hills.

  Without turning he said: "Well, Bryne?"

  Behind him Bryne laughed.

  "How did you know?"

  Fenton straightened and turned. Bryne leaned in the open doorway, arms folded, sandy brows lifted quizzically.

  "You and I," Fenton said in a deliberate voice, "are the only men who know most of the rabbit-warren secrets in this Unit. Torren knows them all. But it had to be you or Torren, obviously. You know how I knew, Bryne. Are you trying to flatter me? Isn't it a waste of time, now?"

  "That depends on you," Bryne said, adding thoughtfully a moment later, "—and me, of course."

  "Go on," Fenton said.

  Bryne shifted his gaunt body awkwardly against the door.

  "Do you know what orders Torren gave me an hour ago? No, of course you don't. I'll tell you. You're not to be admitted to him again even if you ask, which I told him you wouldn't. You're not to take anything out of the Unit except the clothes you wear, so you can stop packing. Your accounts have been stopped. All the money you're to have is what's in your pocket. This suite is out of bounds as soon as you leave it." He glanced at his wrist. "In half an hour I'm to come up here and escort you to Level Two. You eat with the repair crew and sleep in the crew dormitory until Thursday, when a freighter is due in at the spaceport. You'll sign on with the crew and work your way back to Earth." Bryne grinned. "After that, you're on your own."

  Fenton touched his scarred cheek meditatively, gave Bryne a cold glance.

  "I'll expect you in half an hour, then," he said. "Good-by."

  Bryne stood up straighter. The grin faded.

  "You don't like me," he said, on a note of sadness. "All the same, you'd better trust me. Half an hour's all we have now. After that I pass over into my official capacity as the Protector's representative, and I'll have to carry Torren's orders out. He thinks you need work-hardening. I may find myself finagling you into a slave-contract in the underlands."

  "What do you suggest?" Fenton asked, folding another shirt.

  "That's better." Bryne dropped a hand into his pocket, stepped forward, and tossed a thick packet of money onto the bed. Beside it he dropped a key and a folded ticket, bright pink for first-class.

  "A ship leaves six hours from now for Earth," Bryne said. "There's a tractor car waiting in the gully at the foot of G-Corridor. That's its key. Torren keeps a close watch on all the Corridors, but the system's complex. Now and then by accident one of the wiring devices gets out of order. G-Corridor's out of order right now—not by accident. How do you like it, Fenton?"

  Fenton laid the folded shirt into place, glanced at the money without expression. He was thinking rapidly, but his face showed nothing.

  "What do you stand to gain, Bryne?" he asked. "Or is this one of Torren's subtler schemes?"

  "It's all mine," the gaunt man assured him. "I'm looking toward the future. I'm a very honest man, Fenton. Not direct—no. You can afford to be direct. I can't. I'm only an administrator. Torren's the boss. Some day you'll be boss. I'd like to go on being an administrator then, too."

  "Then this is by way of a bribe, is it?" Fenton inquired. "Waste of time, Bryne. I'm stepping out. Torren's probably rewriting his will already. When I leave Ganymede I leave for good. As if you didn't know."

  "I know, all right. Naturally. I've already been notified to get out the old will. But I'll tell you, Fenton—I like administering Ganymede. I like being cupbearer to the gods. It suits me. I'm good at it. I want to go on." He paused, giving Fenton a keen glance under the sandy lashes. "How much longer do you think Torren has to live?" he inquired.

  Fenton paused in his methodic packing. He looked at Bryne.

  "Maybe a year," Bryne answered his own question. "Maybe less. In his condition he ought to be glad of it. I'm thinking about afterward. You and I understand each other, Fenton. I don't want to see the Torren holdings broken up. Suppose I keep the will that names you inheritor and tear up the new one Torren's going to make today? Would that be worth anything to you?"

  Fenton looked out over the snow toward the turquoise valley where Kristin would be scattering yellow seeds into the furrows of the ploughed Ganymedan soil. He sighed. Then stooped and picked up the money, the ticket and the key.

  "You'll have to take my word for it," he said, "that it would be. But I wish I understood why you're really doing this. I thought you and Torren got along better than that."

  "Oh, we do. We get along fine. But—Fenton, he scares me. I don't know what makes him tick. Funny things are happening to the human race these days, Fenton." Unexpected sincerity showed on the gaunt face in the doorway. "Torren ... Torren isn't human. A lot of people aren't human any more. The important people aren't."

  He swung a long arm toward the turquoise valley. "The Threshold people are getting the upper hand, Fenton. I don't mean here. I don't mean literally. But they're the inheritors of the future, not us. I guess I'm jealous." He grinned wryly. "Jealous, and a little scared. I want to feel important. You and I are human. We may not like each other much, but we understand each other. We can work together." He drew his shoulders together with a small shiver. "Torren's a monster, not a man. You know it, now. I know why you quarreled. I'm glad of it."

  "I'll bet you are," Fenton said.

  -

  When it was safe, he drove the tractor car down the gorge between high banks of snow, rolling as fast as he dared toward the turquoise valley. The Ganymedan landscape framed in the square window openings all around him looked like so many television images on square screens. Probably some of it really was framed upon screens, back there in the Unit whose mile-square walls fell farther and farther behind as the tractor treads ground on.

  Probably Torren's screen, tilted above the water bath, reflected some such landscape as this. But there were often tractor cars trundling along the snowy roads. Unless Torren had reason to suspect, he was not likely to focus too sharply upon this one. Still, Fenton knew he would feel more comfortable after he had passed beyond the range of the 'visor. Not that Torren couldn't summon up a picture of any Ganymedan area he happened to feel curious about. The thing was to keep his curiosity asleep, until the time came to rouse it.

  The cold hills swung by. The heavy air swirled a little as the car spun along, making eddies like paradoxic heat waves between Fenton and the road. No man could live without an insulated suit and breathing-apparatus on the surface of Ganymede—yet. But the specially bred Ganymedans from the Threshold Planetarium could.

  When men first reached the planets they found their thresholds fatally different from Earth. They began to alter the planets, and to alter the men. This after one whole wasted generation in which they tried to establish colonies that could be supported from Earth and could operate from artificial shelters. It didn't work. It never worked, even on Earth, when men tried to create permanent colonies in alien lands without subsisting on the land itself.

  There is more to it than the lack of bread alone. Man must establish himself as a self-sustaining unit on the land he works, or he will not work it. Neither humans nor animals can subsist or function efficiently on alien territory. Their metabolism is geared to a different ecology, their digestive organs demand a different food, melancholia and lassitude overcome them eventually. None of the great bonanza ventures on the mineral-rich planets ever came to a successful production because agriculture could not keep up with them and they collapsed of their own weight. It had been proved true time and again on Earth, and now on the planets the old truism repeated itself.

  So the Threshold Planetaria were set up and the vast experiment got under way. And they altered the planets as well as the stock that was to possess them.

  Ganymede was cold. The atmosphere of heavy gases could not sustain human life. So with atomic power and technological weapons man began to alter the ecology of Ganymede. Through the years the temperature crept gradually up from the deadly level of a hundred degrees below centigrade zero. Wastefully, desperately, the frozen water was released, until a cloud-blanket began to form over Ganymede to hold in the heat.

  There were many failures. There were long periods of inactivity, when the insulated domes were deserted. But as new methods, new alloys, new isotopes were developed, the process became more and more practical. When the final generation of Ganymede-slanted stock was bred, Ganymede was ready for them.

  Since then, three generations had become self-sustaining on the satellite. They could breathe the air—though men could not. They could endure the cold—though men could not. They were taller than men, solider and stronger. There were several thousand of them now.

  As they had driven along a genetic parabola to meet the rising parabola of an altered planetary balance, so now the Ganymedans and Ganymede together followed a new curve. In a few more generations it would circle back to meet normal humanity. By that time, Ganymede should be habitable for Earthmen, and by then Ganymedans should have altered once more, back toward the norm.

  Perhaps the plan was not the best possible plan. Humanity is not perfect. They made many errors, many false guesses, when the Age of Technology began. Balance of power among the nations of Earth influenced the development of the Threshold Planetaria. Social conflicts changed and shifted as civilization found new processes and methods and power-sources.

  Fenton thought of Torren. Yes, there had been many errors of judgment. The children of Torren should have walked like giants upon a free planet. Centrifuge-bred colossi. But that experiment had failed. Not even upon tiny Ganymede could Torren use the tremendous strength inherent in his helpless body to stand upright.

  It was easier to work eugenically with animals. In the new Ganymedan seas, still growing, and on the frigid Ganymedan continents, were creatures bred to breathe the atmosphere—arctic and subarctic creatures, walrus and fish, snow-rabbit and moose. Trees grew on Ganymede now, mutated tundra spread across the barrens, supplemented by the photosynthesis laboratories. A world was being born.

  And across the world marched the heat-giving, life-giving towers built over a hundred-year period by the Earth government, still owned by Earth, not to be touched even by Torren, who owned Ganymede. Fenton swung the tractor over the brow of the hill and paused for an instant to look west. A new tower was rising there, one of hundreds, to supplement the old towers with a new method of speeding up changes. Within ten years these snowy hills might ripple with wheat—

  The road forked here. One way led toward the valley. The other lay like a long blue ribbon across the hilltops, dipping suddenly as the horizon dipped toward the spaceport and the ship that was headed for home.

  Fenton touched the scar on his cheek and looked at the spaceport road. Earth, he thought. And then? He thought of Bryne's wise, gaunt face, and of Torren wallowing in his water bed that was linked like the center of a spider's web with every quarter of the mile-square Unit and every section of the little globe it stood on. No, not a spider web—an island. A floating island with no link that bound him to humanity.

  Fenton spoke one furious word and wrenched violently at the wheel. The car churned up snow in a blinding haze and then leaped forward along the right-hand road, down toward the turquoise mist that hid the valley.

  -

  An hour later he came to the village called Providence.

  The houses were of local stone, with moss-thatched roofs. Early experiments with buildings of metal, plastics and imported wood had been discarded, as might be expected, in favor of indigenous materials. For life on Ganymede no houses proved quite so satisfying as houses built of Ganymede stone.

  The people came mostly of hardy Norse stock, with Inuit and other strains mingled for the desirable traits. The Ganymedans who came out into the snow-powdered street when Fenton stopped his car were an entirely new race. An unexpectedly handsome race, since they had certainly not been bred for beauty. Perhaps much of their good looks sprang from their excellent health, their adjustment to their lives and their world, the knowledge that the world and the work they did upon it were both good and necessary. Until now.

  A big yellow-haired man in furs bent to the window of the car, his breath clouding the heavy air which no normal human could breathe.

  "Any luck, Ben?" he asked, his voice vibrating through the diaphragm set in the side of the car. It was only thus that a Ganymedan could speak to an Earth-born human. Their voices had to filter to each other through carbon dioxide air and metal and rubber plates. It meant nothing. There are higher barriers than these between human minds.

  "About what you expected," Fenton told him, watching the diaphragm vibrate when sound struck it. He wondered how his own voice sounded, out there in the cold air heavy-laden with gases.

  Yellow heads and brown nodded recognition of what he meant. The tall people around the car seemed to sag a little, though two or three of them laughed shortly, and one big woman in a fur hood said:

  "Torren's fond of you, Ben. He must be, after all. Maybe—"

  "No," Fenton told her positively. "He's projected himself in my image, that's all. I can walk around. But I'm simply an extension, like an arm or a leg. Or an eye. And if Torren's eye offends him—"

  He broke off abruptly, slapped the steering wheel a couple of times and looked ahead of him down the wide, clean street lined with clean, wide-windowed houses that seemed to spring from the rock they stood on. They were strong houses, built low to defy the blizzard winds of Ganymede. The clear, wide, snowy hills rolled away beyond the rooftops. It was a good world—for the Ganymedans. He tried to think of these big, long-striding people shut up in asylums while their world slowly changed outside the windows until they could no longer breathe its air.

  "But, Ben," the woman said, "it isn't as if people needed Ganymede. I wish I could talk to him. I wish I understood—"

  "Have you any idea," Fenton asked, "how much Torren spends in a year? People don't need living room on Ganymede, but Torren needs the money he could get if ... oh, forget it. Never mind, Marta."