Then he was through the pond, and the Deck surface hurtled up to meet him, unimaginably hard.

The tetrahedron was liberally coated with dust. Mark had the ’bot roll forward and wipe the building’s surface, tentatively. Beneath a half-inch thickness of the dust, the material of the tetrahedron’s construction was milky-white, seamless. The triangular faces gave the structure the look of something flimsy, or temporary, Lieserl thought — like a tent of cloth.

It had been Mark’s suggestion for them to approach this structure in human form. “We want to know — among other things — if people built this thing, and why,” he had argued. “How else are we going to get a genuine feel for the place, unless we look at it through human eyes?” Lieserl hadn’t been sure. To restrict themselves to human form — more than was necessary to interface with Uvarov — had seemed inefficient. But, staring at the structure now, Lieserl realized what a good idea it had been.

“It’s a tetrahedron,” Lieserl observed. “Like an Interface portal.”

“Well, that’s a characteristic signature of human architecture,” Mark murmured. “Doesn’t mean a thing, by itself, though. And from the thickness of that dust, I guess we know this place has been abandoned for a long time.”

“Hmm. The door looks human enough.”

The door was a simple hatchway seven feet tall and three wide, set at the base of one of the tetrahedron’s triangular walls. There was a touchpad control, set at the waist height of an average human.

Mark shrugged. “Let’s try to open it.”

The ’bot rolled forward silently, bouncing a little on the rough surface despite its fat, soft wheels. It extended an arm fitted with a crude mechanical grab, tapped cautiously at the door, and then pushed at the control pad.

The door slid aside, into the fabric of the tetrahedron. A puff of air gushed out at them. A few scraps of dust tumbled out, and, when the air had dispersed, the dust fell in neat parabolae to the surface.

Beyond the door there was a small rectangular chamber, big enough for four or five people. The walls were of the same milky substance as the outer shell, and were unadorned. There was another door, identical to the first, set into the far wall of the chamber.

“At least we know there’s still power,” Mark said.

“This is an airlock,” Lieserl said, looking inside the little chamber. “Plain, functional. Very conventional. Well, what now? Do we go in?”

Mark pointed.

The ’bot was already rolling into the airlock. It bumped over the lip, and came to a halt at the center of the lock.

Lieserl and Mark hesitated for a few seconds; the ’bot waited patiently inside the lock.

Mark grinned. “Evidently, we go in!”

He held out his arm to Lieserl. Arm in arm, they trooped after the robot into the lock.

The lock, containing the ’bot and the two of them, was a little cramped. Lieserl found herself shying away from the ’bot’s huge, dusty wheels, as if she might get her environment suit smeared.

The ’bot reached out and pushed the control to open the next door. There was a hiss of pressure equalization.

The ’bot exposed an array of chemical sensors, and Mark cracked open his faceplate and sniffed elaborately.

“Oh, stop showing off,” Lieserl said.

“Air,” he said. “Earth-normal, more or less. A few strange trace elements. No unusual smells — and quite sterile. We could breathe this stuff if we had to, Lieserl.”

The lock’s inner door swung open, revealing a larger chamber. The ’bot pushed a lamp, magnesium-white, into the chamber, and light flared from the walls. Lieserl caught a glimpse of conventional-looking furniture: beds, chairs, a long desk. The chamber’s walls sloped upwards to a peak; this single room looked large enough to occupy most of the tetrahedral volume of the building.

The ’bot rolled forward. Mark stepped briskly out of the lock and into the chamber; Lieserl followed.

“Mark Wu? Lieserl?” Uvarov’s rasp was loud in her ear.

“Yes, Doctor,” Lieserl replied. “We hear you. You don’t need to shout.”

“Oh, really,” Uvarov said. “Unlike you, I didn’t simply assume that our transmissions would carry through whatever those walls are made of.”

Lieserl smiled at Mark. “Were you worried about us, Uvarov?”

“No. I was worried about the ’bot.”

Lieserl stepped toward the center of the main chamber and looked around.

The walls of the tetrahedral structure sloped up around her, coming to a neat point fifteen feet above her head. She could see partitioned sections in two of the corners. Bedrooms? Bathrooms? A galley, perhaps?

The ’bot scurried around the edge of the room, its multiple arms probing into corners and edges. It left planet-dust tracks behind itself.

The main piece of furniture was a long desk, constructed of what looked — for all the world — like wood. Lieserl could see monitors of some kind inlaid into the desk surface. The monitors were dead, but they looked like reasonably conventional touch-screens. Lieserl reached out a gloved hand, wishing she could feel the wood surface.

There were chairs, in a row, before the desk — four of them, side by side. These were obviously of human construction, with upright backs, padded seats, and two arms studded with controls.

“Mark, look at this,” she said. “These chairs would fit either of us.”

Mark had found something — two objects — at the end of the desk; he had the ’bot roll across and pick the objects up. Mark’s face was lit with wonder; he bent to inspect the first object, held before him in the ’bot’s delicate grab. “This is some kind of stylus,” he said. “Could be something as simple as an ink pen…” The ’bot held up the second object. “But this thing is unmistakable, Lieserl. Look at it. It’s a cup.” His hands on his knees, he looked up at her. “The builders of this place must have been gone a million years. But it’s as if they just stepped outside.”

Uvarov rasped, “Who? I wish you’d speak to me, damn it. What have you found?”

Mark and Lieserl looked at each other.

“People,” Lieserl said. “We’ve found people, Uvarov.”

Mark sat with Louise in her oak-paneled bedroom inside the Great Britain. Mark had called up a Virtual schematic of the Northern’s lifedome; the schematic was a cylinder three feet tall, hovering over her bed. The schematic showed a lifedome which sparkled with glass and light, and the greenery of the forest Deck glowed under the skydome at the crown.

Louise felt something move inside her; the lifedome looked so beautiful — so fragile.

She stared around at the familiar polished walls of her room — it was actually two of the old ship’s state rooms, knocked together and converted. Here was the center of her world, if anywhere was; here were her few pieces of old furniture, her clothes, her first, antique data slate — which still contained the engineering sketches of the Great Britain she’d prepared during her first visit to the old ship as a teenager, five million years and half a Universe away. If only, she thought, if only she could pull this room around her like some huge wooden blanket, never to emerge into the complex horrors of the world…

But here was Mark, politely sitting on the corner of her bed and watching her face. And now he said quietly: “Here it comes, Louise.”

She forced herself to look at the Virtual of the lifedome.

Mark pointed at the mid-section of the lifedome. A horizontal line of blue-white light appeared; it shimmered bale-fully against the clear substance of the lifedome, like a sword blade.

“The string has sliced into us from this side. I guess we can be grateful the relative velocity was actually quite low…”

The string cut easily into the substance of the dome, like a hot wire into butter.