Horza looked round, orienting himself with the grid pattern shown on the screen. "Would that thing be fooled by a pile of uranium?"

"Oh yeah," Wubslin said, nodding. "The power we're putting through it, any radiation will upset it a bit. That's why we're down to roughly thirty kilometres maximum anyway, see? Just because of all this granite. Yeah, if there's a reactor, even an old one, it'll show up when the sensor's reader waves get to it. But just like this, as a patch. If this Mind's only fifteen metres long and weighs ten thousand tonnes, it'll be really bright. Like a star on the screen."

"OK," Horza said. "That's probably just the reactor down at the deepest service level."

"Oh," Wubslin said. "They had reactors, too?"

"Back-up," Horza said. "That one was for ventilation fans if the natural circulation couldn't cope with smoke or gas. The trains have reactors, too, in case the geothermal failed." Horza checked the reading on the screen with the built-in mass sensor in his suit, but the faint trace of the back-up reactor was out of its range.

"Should we investigate this one?" Wubslin asked, his face lit by the glowing screen.

Horza straightened up, shaking his head. "No," he said wearily. "Not for now."

They sat in the station and had something to eat. The station was over three hundred metres long and twice the width of the main tunnels. The metal rails the Command System trains ran on stretched across the level floor of fused rock in double tracks, appearing from one wall through an inverted U and disappearing through another, towards the repair and maintenance area. At either end of the station there were sets of gantries and ramps which rose almost to the roof. Those provided access to the two upper floors of the trains when they were in the station, Horza explained when Neisin asked about them.

"I can't wait to see these trains," Wubslin mumbled, mouth full.

"You won't be able to see them if there's no light," Aviger told him.

"I think it's intolerable that I have to go on carrying all that junk," the drone said. It had set the equipment-loaded pallet down. "And now I'm told I have to carry even more weight!"

"I'm not that heavy, Unaha-Closp," said Balveda.

"You'll manage," Horza told the machine. With no power the only thing they could do was use their suits" AG to float along to the next station; it would be slower than the transit tube, but quicker than walking. Balveda would have to be carried by the drone.

"Horza… I was wondering," Yalson said.

"What?"

"How much radiation have we all soaked up recently?"

"Not much." Horza checked the small screen inside his helmet. The radiation level wasn't dangerous; the granite around them gave off a little; but even if they hadn't been suited up, they'd have been in no real danger. "Why?"

"Nothing." Yalson shrugged. "Just with all these reactors, and this granite, and that blast when the bomb went off in the gear you vac'd from the CAT… well, I thought we might have taken a dose. Being on the Megaship when Lamm tried to blow it apart didn't help, either. But if you say we're OK, we're OK."

"Unless somebody's particularly sensitive to it, we haven't got much to worry about."

Yalson nodded.

Horza was wondering whether they should split up. Should they all go together, or should they go in two groups, one down each of the foot tunnels which accompanied the main line and the transit tube? They could even split up further and have somebody go down each of the six tunnels which led from station to station; that was going too far, but it showed how many possibilities there were. Split up, they might be better placed for a flanking attack if one group encountered the Idirans, though they wouldn't initially have the same firepower. They wouldn't be increasing their chances of finding the Mind, not if the mass sensor was working properly, but they would be increasing their chances of stumbling into the Idirans in the first place. Staying together, though, in the one tunnel, gave Horza a feeling of claustrophobic foreboding. One grenade would wipe them out; a single fan of heavy laser-fire would kill or disable all of them.

It was like being set a cunning but unlikely problem in one of the Heibohre Military Academy's term exams.

He couldn't even decide which way to head. When they'd searched the station, Yalson had seen marks in the thin layer of dust on the foot-tunnel floor leading to station five, which suggested the Idirans had gone that way. But ought they to follow, or should they go in the opposite direction? If they followed, and he couldn't convince the Idirans he was on their side, they'd have to fight.

But if they went in the other direction and turned the electricity on at station one, they'd be giving power to the Idirans as well. There was no way of restricting the energy to one part of the Command System. Each station could isolate its section of track from the supply loop, but the circuitry had been designed so that no single traitor — or incompetent — could cut off the whole System. So the Idirans, too, would have use of the transit tubes, the trains themselves and the engineering workshops… Better to find them and try to parley; settle the issue one way or the other.

Horza shook his head. This whole thing was too complicated. The Command System, with its tunnels and caverns, its levels and shafts, its sidings and loops and cross-overs and points, seemed like some infernal closed-circuit flow chart for his thoughts.

He would sleep on it. He needed sleep now, like the rest of them. He could sense it in them. The machine might get run down but it didn't need sleep, and Balveda still seemed alert enough, but all the rest were showing signs of needing a deeper rest than just sitting down. According to their body clocks it was time to sleep; he would be foolish to try to push them further.

He had a restrainer harness on the pallet. That should keep Balveda secure. The machine could stand guard, and he would use the remote sensor on his suit to watch for movement in the immediate area where they slept; they ought to be safe enough.

They finished their meal. Nobody disagreed with the idea of turning in. Balveda was trussed in the restrainer harness and barricaded in one of the empty store rooms off the platform. Unaha-Closp was told to sit itself up on one of the tall gantries and stay still unless it heard or saw anything untoward. Horza set his remote sensor near where he would sleep, on one of the lower girders of a hoist mechanism. He had wanted a word with Yalson, but by the time he had finished making all these arrangements several of the others, including Yalson, had fallen asleep already, lying back against the wall or laid out on the ground, their visors blanked or their heads turned away from the weak lights of the others" suits.

Horza watched Wubslin wander around the station for a bit, then the engineer, too, lay down, and everything was still. Horza switched the remote sensor on, primed to alarm if it sensed anything above a certain low level of movement.

He slept fitfully; his dreams woke him.

Ghosts chased him in echoing docks and silent, deserted ships, and when he turned to face them, their eyes were always waiting, like targets, like mouths; and the mouths swallowed him, so that he fell into the eye's black mouth, past ice rimming it, dead ice rimming the cold, swallowing eye; and then he wasn't falling but running, running with a leaden, pitch-like slowness, through the bone cavities in his own skull, which was slowly disintegrating; a cold planet riddled with tunnels, crashing and crumpling against a never-ending wall of ice, until the wreckage caught him and he fell, burning, into the cold eye tunnel again, and as he fell, a noise came, from the throat of the cold ice-eye and from his own mouth and chilled him more than ice, and the noise said: