The corvette stopped briefly at Saturn. Pirius and Torec knew that name, for this immense gas giant had famously been requisitioned long ago by the Navy as its largest base in Sol system.

Pirius peered out in awe. Around the cloud-draped planet, ships and facilities orbited in swarms. Even the moons bristled with factories and weapons emplacements — though it turned out that many of the smaller moons had been broken up for raw materials, water-ice of mantles and rock of cores.

Nilis waxed nostalgic about this world. He even showed Pirius Virtuals of how it had been before the arrival of humans, when it had been circled by a spectacular system of ice rings. But the rings had been too tempting a mine for the first settlers of the system, and too fragile to withstand the fires of the first wars fought here.

Scenery didn’t interest Pirius much. As a Navy brat, he was much more intrigued by military hardware. So he watched a steady stream of ships plunging into the planet’s clouds. Nilis said that the ships were descending to Saturn’s rocky heart, itself a planetoid about the size of the Earth and immersed in a hydrogen ocean thousands of kilometers deep. In the atrocious conditions of that deep murk, out of sight even of the rest of humanity, huge machines were being built.

Earth, this remote speck of rock at the Galaxy’s rim, was still the logical center of humanity. The Interim Coalition of Governance exerted a tight control on a Galaxy full of human beings, and the epicenter of that control was here, on Earth. If worst came to worst — if the Xeelee ever broke out of the Galaxy’s Core and struck at Sol system itself — Saturn would be the bastion of the last defense of Earth, and those mighty engines would come to life.

The corvette was here because the Xeelee nightfighter captured by Pirius Blue had been hauled across the Galaxy and placed in orbit among Saturn’s moons.

“There was really no other choice,” Nilis murmured. “Bringing back a Xeelee has been enough of a sensation as it is. At least here it will be under Navy guard. If we took it deeper into the inner system we’d be asking for trouble.”

Pirius said, “You mean the risk to Earth would be too great?”

“Oh, no, Pirius, not that. We have come here not to protect mankind from our Xeelee, but to protect the Xeelee from us.” He winked.

After six hours, the corvette slid cautiously away from Saturn and its cordon of technology. As it was carrying celebrities of various degrees of reluctance, the corvette’s crew were granted permission to shorten the remainder of the trip by using their FTL drive within the boundaries of Sol system.

So Pirius saw Saturn wink out of existence, to be replaced immediately by a wall of light, blue- white, that flooded the corvette with dazzling brilliance.

At first Pirius and Torec couldn’t understand what they were seeing. It was an immense shield of blue-gray, almost like metal, that curved smoothly away on all sides. It even looked polished, for Pirius saw a dazzling highlight from the sun. And yet the surface was subtly textured, and there were flaws, darker masses scattered irregularly across the shining surface. Each such mass was surrounded by a fringe of paler blue, flecked with white. Other objects crawled across the shield, trailing arrow- shaped wakes behind them.

Nilis seemed to have anticipated their difficulty. Rather than explain, he encouraged them to use the corvette wall’s magnification facility, to explore the view and figure it out for themselves. Slowly the strange truth of what they were seeing opened up in Pirius’s mind.

He was looking down at a planet, a hemisphere dominated by a single great ocean — an ocean of water, open to the sky. It was kept liquid not by technology, but by thermodynamic equilibrium; its curved surface not shaped by human design, but following a simple gravitational equipotential. Even the wispy clouds he saw were water vapor. Although humanity had by now mapped the Galaxy, this was still, remarkably enough, the largest open-water ocean encountered anywhere.

This was Earth.

Those crawling forms were ships, scudding like insects over the ocean’s surface. But some of the larger forms looked oddly familiar. They turned out to be Spline, which had themselves evolved on a watery world, and now gamboled ponderously in the deep-ocean waves of the Pacific. After millennia of war, the seas of Earth had become a nursery for living starships. But the Spline schools weren’t the strangest thing Pirius saw.

He focused on an island, one of the irregular masses of rock that protruded into the air from the ocean’s patient hide. He peered down at buildings, docks, landing strips. He could even see people moving between the buildings. One little girl, skipping down a path to a beach, glanced up at the sky, as if she could see him staring down at her. Her face was a tiny button. And she was quite naked; the child wore no mask, no skinsuit, no protection of any kind — naked and in the open.

It was too much. Pirius and Torec fled to the enclosed security of their cabin, where they clung to each other, trembling. But they could feel the corvette shudder subtly as it dipped into the air of Earth.

After their landing at a spaceport, a small bubbletop flitter took them in a short suborbital hop to their final destination, Nilis’s home.

As the flitter shot briefly back out of the atmosphere Pirius saw that the primary spaceport had been at the heart of one of the larger land-masses. Now the flitter took them over a strip of ocean to a large offshore island. On this island Pirius spotted crumpled hills and rocky outcrops, obviously natural formations, no use to anybody. In the lowlands, though, and near the coasts and along the river valleys, the land was covered by wide green rectangles and cut through by arrow-straight canals.

But this cultivated land was marred by clusters of silver-gray, irregular, bubbling masses, like blisters. You could see these were not the work of humans, for they lacked both the symmetry of deliberate human design and the more organic patterns of unplanned settlements. But these alien scars were the cities of mankind, Pirius learned; they were called Conurbations.

Conurbations were officially referred to only by numbers. Thus the corvette had landed at the fringe of Conurbation 2807, while the flitter would bring them to Conurbation 3474, a sprawling city surrounding a broad, languid river. These numbers had been assigned by the long-vanquished Qax — pronounced Kh-axe, the alien occupiers of Earth in the years before Hama Druz. The huddling domes of the Conurbations, bubbles of blown rock, were essentially Qax designs; they had been preserved as a kind of permanent memorial of that dreadful time. But Nilis, with a wink, told them that the locals referred to their cities by much older, pre-Occupation names, though not a trace of those older settlements had survived the time of the Qax. Thus they had first landed at Berr-linn, and Nilis’s base was in a city called Lunn-dinn.

They landed by the bank of the river, close to one of the great domes of Lunn-dinn. As they prepared to leave the flitter, Pirius glimpsed the river itself, sparkling in the low sun. Even that was a stunning sight: open water, billions of tonnes of it just sliding by, in miraculous equilibrium with an atmosphere that was itself open to space.

It was a short walk through a covered passage from the pad to Nilis’s apartment, which was just inside the skin of the dome. Nilis briskly walked through dusty rooms. Maintenance bots clustered in Nilis’s wake demanding instructions, and self-proclaiming “urgent” Virtuals fluttered around him, evanescent and noisy. There was a musty smell, a faint staleness. It had evidently been some time since he had been home.