bury itself in his back. But it didn't. The other had been taken so completely by surprise that he simply went backwards, suddenly, and with a strangled oath.

Instantly Corriston was on top of him. He shifted his grip, releasing both of the struggling man's ankles and remorselessly seizing his wrists. He raised his right knee and brought it savagely downward, again and again and again. A cry of pain echoed through the darkness. The killer, crying out in torment, tried to twist free.

For an instant the outcome remained uncertain, a see-saw contest of strength. Then Corriston had the knife and the struggle was over.

Corriston made a mistake then of relaxing a little. Instantly, the killer rolled sideways, broke Corriston's grip, and was on his feet. He did not attempt to retaliate in any way. He simply disappeared into the darkness, breathing so loudly that Corriston could tell when the distance between them had dwindled to the vanishing point.

Corriston sat very still in the darkness, holding on tightly to the knife. His triumph had been unexpected and complete. It had been close to miraculous. Strange that he should be aware of that and yet feel only a dark horror growing in his mind. Strange that he should remember so quickly again the horror of a man gasping out his life with a thorned barb protruding from his side.

It had begun a half-hour earlier in the general passenger cabin. It had begun with a wonder and a rejoicing.

Tremendous and glittering, the Space Station had come floating up out of the Big Dark like a golden bubble on an onrushing tidal wave. It had hovered for an instant in the precise center of the viewscreen, its steep, climbing trail shedding radiance in all directions. Then it had descended vertically until it almost filled the lower half of the screen, and finally was lost to view in a wilderness of space.

When it appeared for the second time, it was larger still and its shadow was a swiftly widening crescent blotting out the nearer stars.

"There it is!" someone whispered.

It had been unreasonably quiet in the general passenger cabin, and for a moment no other sound was audible. Then the whisper was caught up and amplified by a dozen awestruck voices. It became a murmur of amazement and of wonder, and as it increased in volume, the screen seemed to glow with an almost unbelievable brightness.

Everyone was aware of the brightness. But how much of it was subjective no one knew or cared. To a man in the larger darkness of space, a dead sea bottom on Mars, or a moon-landing ship wrapped in eternal darkness on a lonely peak in the Lunar Apennines may glow with a noonday splendor.

"They said a space station that size could never be built," David Corriston said, leaning abruptly forward in his chair. "They quoted reams of statistics: height above the center of the Earth in kilometers, orbital velocity, relation of mass to maneuverability. The experts had a field day. They went far out on a limb to convince anyone who would listen that a station weighing thousands of tons would never get past the blueprint stage. But the men who built it had enough pride and confidence in human skill to achieve the impossible."

The girl at Corriston's side looked startled for an instant, as though the ironclad assurance of so young a man was as much of a surprise as his unexpected nearness, and somehow even more disquieting older.

She was certainly somewhat older than he was—about three or four years. She was an exceptionally pretty girl, her fair hair fluffed out from under a blue beret, her ship's lounge jacket a youth-accentuating miracle of casual tailoring that would have looked well on a woman of any age. She had the kind of eyes Corriston liked best of all in a woman: longlashed, observant, and bright with glints of humor.

She had the kind of mouth he liked too—a mouth which suggested that she could be, by turns, capricious, level-headed, and audaciously friendly with strangers without in any way inviting familiarity. There was a certain paradoxical timidity in her gaze too. It was manifesting itself now in an obvious reluctance to be startled too abruptly by space engineering talk from a young man who had taken her companionability for granted and who was obviously given to snap judgments.

She brushed back the hair on her right temple, her brown eyes upraised to study Corriston more closely.

He hoped that she would realize upon reflection that she was behaving foolishly. He had taken a certain liberty in talking to her as he would have talked to an old acquaintance in a long-awaited meeting of minds. On the big screen a space station that couldn't be built was sweeping in toward the ship with eighty-five years of unparallelled scientific progress behind it.

First had come the Earth satellites, eight of them in their neat little orbits. They had used low-energy fuels, had kept close to the Earth, and no one had seriously expected them to do more than record weather information and relay radio signals. For fifteen years they could be seen with small telescopes and even with the unaided eye on bright, cloudless nights in both hemispheres.

First had come these small, relatively unimportant artificial moons and then, on a night in October 1972, the first space platform had been launched. Soon the sky above the Earth was swarming with radar warning platforms, a dozen men to operate them, and carrier-based jets equipped with formidable atomic warheads.

Nevertheless, how could anyone have known that in another twenty years interplanetary space flight would become a war-averting reality? How could anyone have known that by the year 2007 there would be human settlements on Mars and by the year 2022 the actual transportation to Mars of city-building materials?

2

Corriston was beginning to feel uncomfortable. He wished that the girl would say something instead of just continuing to stare at him. She seemed to be interested in his uniform. She appeared to be gazing at him interrogatively, as if she wanted to know more about him before promising anything.

He wondered what her unconscious purpose was. Did she see in him the quiet, determined type who was all set to accomplish something important. Or was she regretting he wasn't the hard-living, cynical type who had been everywhere and done everything?

Well, one way to find out was to be himself: a man average in every way, but with a hard core of idealism in his nature, a creative mind and enough independence and self-assurance to give a good account of himself in any struggle which brought his central beliefs under fire or placed them in long-range jeopardy.

And so Corriston suddenly found himself talking about the Station again.

"Not many people have grasped the importance of it yet," he said. "One station will service our needs, instead of fifty-seven, one tremendous central terminal and re-fueling depot for all of the ships. Do you realize what that could mean?"

Abruptly there was a startling warmth in the girl's eyes, an unmistakable look of interest and encouragement.

"Just what could it mean?" she asked.

"Any kind of steady growth across the years leads to centralization, to bigness. And that bigness becomes time-hallowed and magnified out of all proportion to its original significance. The Space Station is no exception. It started with the primitive Earth satellites and branched out into fifty-seven larger stations. Now it's tremendous, a single central station that can impose its influence in ship clearance matters with an almost unanswerable finality."

A shadow had come into the girl's eyes. "But not completely without checks and balances. The Earth Federation can challenge its supremacy at any point."

"Yes, and I'm glad that the challenge remains a factor to be reckoned with. As matters stand now the Station's prestige can't be implemented with what might well become the iron hand of an intolerable tyranny. As matters stand, the