The train drew into Moorgate station, just behind the foot of the northern endcap. Greg stepped out of the coach, finding himself in a large oblong rock chamber, with six platforms laid out in parallel. It was obviously a staging area for the crews digging the second chamber. Rails disappeared up four smaller tunnels in the north wall. Beyond the last platform there was a collection of heavy machinery laid out like a small town; lorry-sized electrical transformers, big spherical tanks, and the ribbed cylinders of turbo-pump casings. A crisscross grid of two-metre pipes, heavy-duty plastic tubes, and thick power cables led away from them into eight service tunnels.

Moorgate station was deserted except for Bernard Kemp and a youngish WPC who were standing waiting on the platform.

Bernard Kemp's mood hadn't improved, Greg observed. The sergeant gave Sinclair a look of undisguised contempt, then started when Julia emerged from the coach. The WPC came to attention.

Julia lifted her hand in an airy gesture. "There's no need for that," she told the woman.

"We've secured the station, sir," Bernard Kemp told Greg as the crash team piled out of the coach. "And the transport controller has shut down this line's traffic: there'll be no more coaches in. All the construction and mining crews in the second chamber will use the Lancaster Gate station when they come off shift." He watched the coach carrying the remainder of the crash team glide to a halt. "Exactly what is going on, sir, ma'am?"

"Just like the Governor says, a biohazard alert," Greg said.

"A biohazard?"

"Yeah. But not a biology we know much about. OK?" Greg didn't even want to tell him that, God alone knew what kind of rumours it would start, but he felt he owed the sergeant something for all the inconvenience.

"Yes, sir," Bernard Kemp said reluctantly. His eyes kept wandering back to Julia.

"Right, now you two take one of our coaches, and report back to your headquarters," Greg told the sergeant. He waited until the door slid shut behind them, then turned to Sinclair. "OK. Where now?"

Sinclair looked at the crash team and sighed. "The Celestial Apostles, we had something… good. Nothing grand, I do declare, no utopia, but we got along fine. The only quarrels were the quarrels that people should have, little things by the by. We all believed together, you see; that was enough to bind us."

"But that was all due to change tomorrow anyway, right?" Greg asked.

"Ah, now, Captain Greg, there you go again. Spoiling me rhythm, just when I was working up a fine head of indignation. You're a hard man, you are. No respect." He gave Julia a mocking smile. "I'm surprised at you, a lady with a vision past mine. You shouldn't be associating with the likes of him. Terribly bad for you, it is."

"No, it isn't," Julia said. "Greg's one of my real friends."

"Oh, Holy Mary, and I'm to deliver us into your tender hands, am I? Lord forgive me." He dropped over the side of the platform with surprising ease, and started walking down the rail towards the north wall.

Greg landed lightly behind him, then turned to help Julia. The crash team began to jump down, the resonant hammer blows of their boots hitting the rock echoing round the silent chamber.

Sinclair looked round, and muttered a despairing, "Jesus." Greg took the lead as Sinclair led them past the rail tunnels, heading towards the heavy machinery at the end of the chamber. A small secretion awoke his intuition, and allowed him to expand his espersense. The three psychics in the crash team had used their sacs to activate their own psi abilities. They all exchanged mental grins of acknowledgement.

It was going to be one of the service tunnels that carried pipes and cables up to the second chamber, Greg decided. He whispered a request for a link to Melvyn Ambler into his throat mike. "Melvyn, I'll go in on Sinclair's heels, but I want two of your tech specialists behind me. I'll know if we're heading into anything lethal, or if Sinclair's brewing up trouble. But there are bound to be sensors."

"Roger," Melvyn acknowledged. "Carlos, Lesley, up front. Ms Evans, could you and Rick move into the middle of the team, please?"

Greg sensed the beginnings of resentment rustling round in Julia's mind. He ordered the communication circuit off. "Best place," he said, and held her eye.

"Yeah, all right."

Sinclair walked into one of the service tunnels, a simple tube three metres in diameter. Inside was a remote, basic world; walls scored by the blades of the mining machine which had cut it, a metre-wide pipe fastened to the rock at waist height by solid metal brackets, cables strung from the ceiling in long hoops which made him duck every few metres. The rock was cold, leaching warmth from the air, minute beads of condensation clung to every surface. Long oblong grids had been laid down to give a narrow level floor. Dim biolum panels were stuck to the wall every five metres. Greg could see a tiny silver trickle of water underneath the metal grid.

He reckoned they'd gone about seventy metres when Sinclair halted.

"Would you be so kind as to give me a hand here, Captain Greg?" Sinclair asked as he bent over. "Me back isn't what it used to be."

He stuck a couple of fingers through the grid, and fished up a wire hoop. "Here we go. Just tug on that. It'll come up like a trapdoor."

Greg sensed a tingle of satisfaction in Sinclair's thought currents, nothing malicious.

"I'm registering some magnetic patterns," Carlos said. "They came on when Sinclair picked up that loop. This section of the tunnel is wired. Something just above you, sir, small and delicate. Probably a photon amp and mike. I'm jamming the processor."

"Will they know that?" Greg asked.

"Not unless it was military grade hardware; it should just seem as though the hardware is down."

Greg couldn't believe the Celestial Apostles would use military 'ware. They'd know someone was coming, but not who. He got a grip on the hoop, and pulled. It was heavier than he expected.

The grid came up with a loud squeak, revealing solid darkness. He slipped the energy dissipater suit's hood over his head, feeling the wet lick of the photon amp adhering to the skin round his eyes. His universe shifted to a weathered blue and grey grisaille, and the darkness receded.

There was a large crack running along the bottom of the tunnel. It had been widened below the grid, chiselled away with some kind of power tool. The jagged hole was over a metre wide, rough-hewn steps leading downwards. He bled in the infrared, adding a faint pink hue to the image. But there were no hot spots, no sign of life.

"Is there anybody on duty below?" Greg asked.

"Certainly not, Captain Greg. What would we be wanting with look outs? We're not criminals, we're believers."

Greg hopped across the hole to Sinclair. There wasn't room in the tunnel to get past anyone. He probed round with his espersense, the crash team invading his consciousness, a complicated mélange of emotions. Nobody else.

"Melvyn, it's clear for the first fifteen metres."

"Roger. Carlos, Lesley, secure the entrance please."

The first armoured figure waddled gracelessly up to the lip of the hole, massive in the restricted width of the tunnel. Infrared picked out ruby shimmers around its joints, fluctuating at each movement. Greg wondered if any of them would be able to fit down the steps.

Carlos held out an arm and dropped a thick ten-centimetre reconnaissance disk down into the hole. Greg watched the miniature UFO swoop into the cave, its motor glowing, tracing a crimson line that curved through the air like a bent laser beam.

"No hazards visible," Carlos reported. He started down the steps. His arms scraped the rock on either side, sending up a burst of vivid orange sparks.

Greg winced.