And at last, he thought, at last I will burst through the Sky. And then there will be no more Culls.

Shrieking, he dissolved into the base Cull floor.

The flitter was new, cramped and smelled of smooth, clean plastic, and it descended in silence save for the precise hiss of its jets. It crunched gently into the surface of Nereid, about a mile from Marsden’s dome.

Chen peered through the cabin windows at the shabby moonscape. Marsden’s dome was just over the compact horizon, intact, sleek, private. “Lethe,” Chen said. “I always hated assignments like these. Loners. You never know what you’re going to find.”

Hassan laughed, his voice obscured as he pulled his face plate down. “So easily shocked? And I thought you police were tough.”

“Ex-police,” Chen corrected automatically. She waved a gloved hand at the dome. “Look out there. What kind of person lives alone, for years, in a forsaken place like this?”

“That’s what we’ve been sent to find out.” Bayliss, the third person in the flitter, was adjusting her own headgear with neat, precise movements of her small hands. Chen found herself watching, fascinated; those little hands were like a bird’s claws, she thought with faint repulsion. “Marsden was a fine physicist,” Bayliss said, her augmented eyes glinting. “Is a fine physicist, I mean. His early experimental work on quantum nonlinearity is still—”

Hassan laughed, ignoring Bayliss. “So we have already reached the limits of your empathy, Susan Chen.”

“Let’s get on with this,” Chen growled.

Hassan cracked the flitter’s hatch.

One by one they dropped to the surface, Chen last, like huge, ungainly snowflakes. The Sun was a bright star close to this little moon’s horizon; knife-sharp shadows scoured the satellite’s surface. Chen scuffed at the surface with her boot. The regolith was fine, powdery, ancient. Undisturbed. Not for much longer.

Beyond Marsden’s dome, the huge bulk of Neptune floated, Earth-blue, like a bloated vision of the home planet. Cirrus clouds cast precise shadows on oceans of methane a thousand miles below. The new wormhole Interface slid across the face of Neptune, glowing, a tetrahedron of baby-blue and gold. Lights moved about it purposefully; Chen peered up longingly.

“Look at this moonscape.” Hassan’s dark face was all but invisible behind his gold-tinted visor. “Doesn’t your heart expand in this ancient grandeur, Susan Chen? What person would not wish to spend time alone here, in contemplation of the infinite?”

All loners are trouble, Chen thought. No one came out to a place as remote as this was — or had been anyway, before the wormhole was dragged out here — unless he or she had a damn good reason.

Chen knew she was going to have to find out Marsden’s reason. She just prayed it was something harmless, academic, remote from the concerns of humanity; otherwise she really, really didn’t want to know.

Hassan was grinning at her discomfiture, his teeth white through the gold of his face plate. Let him. She tilted her head back and tried to make out patterns in Neptune’s clouds.

There were a couple of subsidiary structures: lower domes, nestling against the parent as if for warmth; Chen could see bulk stores piled up inside the domes. There was a small flitter, out-moded but obviously functional; it sat on the surface surrounded by a broad, shallow crater of jet-disturbed dust, telltales blinking complacently. Chen knew that Marsden’s GUTship, which had brought him here from the inner System, had been found intact in a wide orbit around the moon.

It was all bleak, unadorned; but it seemed in order. But if so, why hadn’t Marsden answered his calls?

Hassan was an intraSystem government functionary. When Marsden had failed to respond to warnings about the coming of the Interface colony, Hassan had been sent out here — through the new wormhole — to find out what had happened. He had coopted Bayliss, who had once worked with Marsden — and Chen, who was now working with the Interface crew, but had some experience of walking into unknown, unevaluated situations…

Hassan stepped towards the dome’s doorway. Chen ran her hands without conscious volition over the weapons at her belt. The door dilated smoothly, revealing an empty airlock.

The three of them crowded into the small, upright lock. They avoided each other’s visored eyes while the lock went through its cycle. Chen studied the walls, trying to prepare herself for what she was going to find inside the dome. Just like outside, like Marsden’s flitter, everything was functional, drab, characterless.

Bayliss was watching her curiously. “You’re trying to pick up clues about Marsden, aren’t you? But this is so — bare. It says nothing about him.”

“On the contrary.” Hassan’s voice was subdued, his big frame cramped in the lock. “I think Chen already has learned a great deal.”

The inner door dilated, liquid, silent.

Hassan led them through into the dome. Chen stood just inside the doorway, her back against the plastic wall, hands resting lightly on her weapons.

Silence.

Low light trays, suspended from the ribbed dome, cast blocks of colorless illumination onto the bare floor. One quarter of the dome was fenced off by low partitions; gleaming data desks occupied the rest of the floor area.

Behind the partitions she saw a bed, a shower, a small galley with stacked tins. The galley and bathroom looked clean, but the bedding was crumpled, unmade. After checking her telltales, she cracked her face plate and sniffed the air, cautious. There was a faint smell of human, a stale, vaguely unwashed, laundry smell. There was no color or decoration, anywhere. There was no sound, save for the low humming of the data desks, and the ragged breathing of Hassan and Bayliss.

There was one striking anomaly: a disc-shaped area of floor, ten feet across, glowing softly. A squat cylinder, no bigger than her fist, studded the center of the disc. And something lay across that disc of light, casting huge shadows on the curved ceiling.

Drawn, the three of them moved forward towards the disc of glowing floor.

Bayliss walked through the rows of data desks, running a gloved forefinger gently — almost lovingly — along their gleaming surfaces. Her small face shone in the reflected light of readouts.

They paused on the edge of the pool of glowing floor.

The form lying on the disc of light was a body. It was bulky and angular, casting ungainly shadows on the ribbed dome above.

It was obviously Marsden.

Bayliss dropped to her knees and pressed an analyzer against the glowing surface. Then she ran a fingertip around an arc of the disc’s cloudy circumference. “There’s no definite edge to this. The interior is a lattice of bucky tubes — carbon — laced with iron nuclei. I think it’s some sort of data store. The bucky tube lattice is being extended by nanobots, all around the circumference.” She considered. “Nanobots with fusion pulse jaws… the nanobots are chewing up the substance of the floor and excreting the lattice, patient little workers. Billions of them. Maybe the pool extends under the surface as well; maybe we’re looking at the top surface of a hemisphere, here.”

Chen stepped onto the light and walked to the body. It was face down. It was carelessly bare to the waist, head and face shaven; an implant of some kind was fixed to the wrinkled scalp, blinking red-green. The head was twisted sideways, the eyes open. One hand was buried under the stomach; the other was at the end of an outstretched arm, fingers curled like the limbs of some fleshy crab.

Beneath the corpse, within the glowing floor, light wriggled, wormlike.

He remembered.

With shards of the Cull base floor still glowing faintly around him, he grew once more, biting through postulates, forcing his structure to advance as if by sheer force of will.