"Our trucks. Easy to drive—you'll learn soon. But today, you're just going along for the ride. Keep your eyes peeled."

He unlocked a door and helped her up the high step into the shotgun seat. He paused before closing the door. "I'm sorry I came down on you so hard. I'm sure you understand how important you could be here, and—"

"I don't understand," Patricia said. "I haven't the faintest idea what use I'll be."

Lanier nodded and smiled.

"But you were right, anyway. If I'm so important, then I need to keep my nose to the grindstone."

"Looks like the Stoned work ethic will come natural to you," Lanier said. He climbed into the driver's seat and reached into his pocket, pulling out a slate. He offered it to her. "Slipped my mind. You'll probably want to make notes at some point or other. Government issue."

He switched on the electric motor and drove the truck out of the shed. "We're going into the second chamber now, into the first city. We'll spend a few hours there, then take you on the Thirtieth Century Limited."

"One of the trains?"

He nodded. "We'll skip the third chamber today—too much, too soon. It could overload you. We'll stop at the fourth chamber security compound for a break and lunch, and then go right through to the sixth chamber."

The truck approached a chain link fence stretching for several kilometers east and west.

"Would it be premature to ask questions now?"

"We have to start somewhere," Lanier said.

"That's real dirt outside. You could grow things in it."

"It's moderately fertile," Lanier said. "We have several farming projects under way, mostly in the fourth chamber. Most of the dirt is straight carbonaceous asteroid material, with supplements."

"Mm." She turned to survey the scrub and the low plume of dust behind them. "Is the Stone still powered-up—I mean, can it leave?"

"It's still powered-up," Lanier said. "We don't know whether it can leave or not."

"I was wondering. . . if we could be trapped inside, if it decided to leave. Then we would need to farm, wouldn't we?"

"That's not why we're farming," Lanier said. She waited for him to elaborate, but he stared straight ahead, slowing the truck as they approached the gate in the wire fence.

"The motors are very old. Some of the engineers think they're worn out," he said, as if he had half listened to her and half followed his own chain of thought. He removed an electronic key from his pocket, dialed a number and opened the gate with a radio signal. "We don't understand the drive yet. The motors' last effective act was to slow the Stone down for insertion into the present orbit. They used chunks of mass removed by robots from the outside of the Stone—mostly in the deep bands. Mass-drivers lobbed the chunks towards a point just above the northern crater. That end is sealed off—you'll soon discover a second reason why. What happened to the chunks at that point, we don't know; the documentation is difficult."