"This touching concern for strange kids," Cona said. "It seems slightly out of place in a man who is about to jaunt off to Earth and leave his own son."

"I…"Am not going Dallen prompted himself. Say it right now — I’m not going to Earth. He strove to force the crucial words into being, but all human warmth had fled his soul. He turned away from his wife, sick with disappointment, locked in combat with the chill, haughty, inflexible side of his own nature, and knowing in advance that it was a battle he could never win.

Three hours later Dallen was on the observation gallery of the passenger ship Runcorn as it detached from the docking cradle and climbed away from the humbling and inconceivable vastness of the Orbitsville shell.

The ship was moving very slowly in the early stages of the flight, its magnetic scoop fields unable to gather much reaction mass in a region of space that had been well scoured by other vessels. As a consequence, the one-kilometre aperture around which Beachhead City was built remained visible for some thirty minutes, only gradually narrowing to become a bright ellipse and then a line of light which shortened and finally vanished. But even when the Runcorn was several thousand kilometres into space the inexperienced traveller could have been forgiven for thinking the ship had come to rest only a short distance "above" the shell. At that range Orbitsville was still only half of the visible universe, a seemingly flat surface which occupied a full 180° of the field of vision, the closest approximation in reality to the imagined infinite plane of the geometer.

Also, it was black.

Except in the vicinity of a portal, there was nothing to see when one looked in the direction of Orbitsville, There were no errant chinks of light, no reflections. As far as the evidence of the eye was concerned the familiar cosmos, which was so richly spangled with stars and galaxies and braids of glowing gas, had been sliced in half. There was a hemisphere of sparkling illumination and a hemisphere of darkness — and the latter was the stupendous, invisibly brooding presence that was Orbitsville. And even at a range of a billion kilometres, a distance which light itself took almost an hour to traverse, the sphere was awesome. It registered as a monstrous black hole which had eaten out the centre of the sky.

What, Dallen wondered, must the crew of the Bissendorf have thought when they were making that first approach all that time ago? What was going through their minds as they saw the edges of the dark circle balloon steadily outwards to occlude half the cosmos?

He could imagine those first explorers inclining to the idea that they had encountered a Dyson's Sphere. The 20th Century concept was that, in order to meet all its land and energy requirements, a highly advanced civilisation would eventually need to englobe its parent sun and spread across the inside of the sphere which had been created. A Dyson's Sphere, however, would have been a patchy and inconsistent construct, laboriously cobbled together over many millennia from dismantled planets, asteroids and cosmic debris. And it would have been leaking various kinds of radiation which would have given abundant clues about its true nature.

Orbitsville, in stark contrast, would have remained enigmatic. Its shell of ylem was opaque to everything except gravitation, and therefore the wanderers of the Bissendorf would have known only that they were approaching a sun which had somehow been enclosed within a vast hollow sphere. Their long-range sensors would have told them that the surface of the globe was seamless and as smooth as finely machined steel, but no more information would have been forthcoming.

Even now, two centuries later, man's understanding of the sphere's origins was sharply limited, Dallen reminded himself. It was a study which had yielded little in the way of concrete fact, much in the way of speculation — a field which offered less to pragmatic researchers than to poets and mystics…

How does one account for a seamless globe of ultra-material with a circumference of a billion kilometres? There can be only one source for such an inconceivable quantity of shell material, and that is in the sun itself. Matter is energy, and energy is matter. Every active star hurls the equivalent of millions of tonnes a day of its own substance into space in the form of light and other radiations. But in the case of the Orbitsville sun — once known as Pengelly's Star — the Maker had set up a boundary, turning that energy back on itself, manipulating and modifying it, translating it into matter. With precise control over the most elemental forces of the universe, the maker created an impervious shell of exactly the sort of material He wanted — harder than diamond, immutable, eternal. When the sphere was complete, grown to the required thickness, He again dipped His hands into the font of energy and wrought fresh miracles, coating the interior of the sphere with soil and water and air. Organic acids, even complete cells and seeds, had been constructed in the same way, because at the ultimate level of reality there is no difference between a blade of grass and one of steel…

"Quite a spectacle, isn't it?" The speaker was a young woman who, unnoticed by Dallen had positioned herself beside him at the curving rail of the observation gallery. "It seems to pull your eyes."

"I know what you mean," he said, glancing down at her. The illumination was subdued, most of it from the extravagant blazing of star clouds, but he could see that she had Oriental features and was attractive in a forthright physical manner. He would have guessed she was an athlete or in some way connected with the performing arts.

"This is my first trip to Earth," she said. "How about you?"

"The same." Dallen was intrigued to find that, for one unsettling instant, he had been tempted to pose as a veteran space traveller. "This is all new to me."

"I noticed you coming on board."

Dallen weighed all the connotations of the remark, including her awareness of the fact that he was travelling alone. "You're very observant."

"Not really." The woman locked her gaze with his. "I only see what I like."

"In that case," Dallen said gently, "you're a very lucky person."

He turned away and left the gallery, easily putting the woman out of his thoughts. He was still angry with Cona, still feeling betrayed over their not making the trip as a family, but rebounding to another woman would have been a cheap and ordinary response, the sort of thing that many men would have done, but not Carry Dallen. His best plan, he decided, would be to make maximum use of the ship's gymnasium facilities, burn off his frustrations in sheer physical effort.

All the other passengers appeared to be tourists — couples, family units, dubs, study groups taking advantage of the heavy Metagov subsidy to visit the birthplace of their culture — and Dallen felt himself to be a conspicuously solitary figure as he wound his way through them to fetch his training clothes. The gymnasium was empty when he got there and he went to work immediately, pitting his strength against the resistance frames, repeating the same exercise hundreds of times, aiming for a state of mental and bodily exhaustion which would guarantee his night's sleep.

His scheme was successful to the extent that he fell asleep within minutes of going to bed, but he awoke only two hours later with the depressing knowledge that it was going to be a long, uphill struggle to morning. He tried to pass the time by visualising his new job in Madison City, with all its opportunities for holiday travel to hundreds of fabulous old cities and scenic splendours so conveniently crowded on one tiny planet. But his brain refused to cooperate. No bright visions were forthcoming. As he drowsed through the small hours, in that uneasy margin between wakefulness and sleep where strange terrors prowl. Earth seemed an alien and inimical place.