I watched him moving back to his cave across the snow.

It took me another forty minutes to find it because they can rig this kind of thing in a dozen ways and just because you've disconnected the battery it doesn't mean you won't detonate it if you move too fast or press too hard or touch the wrong terminal, the wrong wire, the wrong connection.

It was lying under the front floorboards. I hadn't been able to see it from underneath the truck: I'd had to go in from the top, prying the floorboards upwards a centimetre at a time and shining the torch beam through the widening gap. I first saw the bomb when the floorboard was still raised only two or three centimetres and I stopped moving at once.

It would depend on how good the man was at his job. He could have used any one of a dozen initiators — chemical, electrical, mechanical, acoustic, vibratory, magnetic — or he could have used a combination initiator to produce detonation whatever I did, so I got a spanner and took the driving mirror off its bracket and slipped it through the gap in the floorboards and used the torch again.

These things are never pleasant to look at, simply because you know what they will do if you disturb them. This one had the squat shape of a giant slug and the stillness of a rattlesnake. Its potential for monstrous havoc gave it, in my mind, a kind of life: the brain refused to believe that this degree of power could be contained in such a small object. What I was looking at was something that could produce an air-blast pressure of a million pounds per square inch and a temperature of four thousand degrees centigrade and a fragmentation velocity of twenty thousand feet per second and it would do this if I made a single wrong move. The infinitely complex system of intelligence inside my skull was within two feet of the source of cataclysmic obliteration, and the forebrain was working out the options while the primitive stem kept the hairs on my arms lifted and the pressure in the arteries raised and the heart's rhythm racing.

But there were no real options. The objective had to be taken across and that was what I was here for and it wasn't the time to weigh values — Karasov's life against mine, the ruthless demands of the mission against the executive's personal survival. I was here because the brink was here and if I'd wanted anything different then I could have walked out of that bloody building in Whitehall long ago and told them to stuff it, get off my back, leave me alone. But they knew what I wanted and they'd put it on the map and set my feet in its direction and told me how far it was and now I was there. On the brink.

You can't keep away, Volodarskiy, can you? You're like me.

I think so, yes.

There's one born every minute.

Time check. 10:53. I'd been here almost an hour and the train from Murmansk was due in at the station in thirty-seven minutes and there wouldn't be a lot of time to check the environment of the freight-yards but if we delayed the rendezvous until 13:00 hours we'd risk exposure and I didn't want to do that, I wanted to get Karasov out before they came for him again.

I moved the mirror in the gap, angling it and sliding it from one end to the other, lighting the underside of the floorboards with the torch. There were no contacts and I pulled the boards higher and took another look. The bomb was the size of a small brick and preserrated with a shrapnel sleeve. The end terminal carried the wire to the junction box underneath the dashboard and the side terminal connected with earth through the chassis: they'd scraped an area clean and used grip tape, a decent enough job. But I didn't like the flat back lever on the underside of the pack and as I turned it a couple of degrees for a better look I realized it was a grasshopper switch and knew that all I had to do was pick up the main pack to send the truck through the roof of the barn, so I worked on the terminals first and freed the pack from the wires and then picked it up slowly, inching my fingers underneath to keep the switch flat to the body.

There was no sound of ticking. A timing device would have been visually evident; all we'd got here was two and a half pounds of TNT and provision for electrical initiation from an outside source and a liquid chemical in a glass tube to detonate internally by percussion: I could see the end of the tube recessed into the main pack and when I tilted it I could see the bubble.

Think. Consider binding the lever with some string and then putting the bomb onto the curved bonnet of the truck and starting the engine and walking away and letting the vibration shake the thing off and send the barn up. It had worked in Berlin and it would work now. The Rinker people weren't likely to come here and poke among the wreckage to make sure there were bodies in it: they'd hear the bang and assume that what had been designed to happen had happened, simply because the human mind prefers to believe in success rather than failure. And even if they came as far as the barn they wouldn't have much time to poke about in the wreckage before Volodarskiy told Fido to tear their throats out.

But it wouldn't work, in the long run. It would mean getting to a phone and asking Fane to organize some more transport for us and that could take days and I didn't know how long Karasov could hold out before his nerves tipped him over the edge and he went stark raving bonkers, which wouldn't please London at all. There was something on that man's mind that wasn't letting him sleep, wasn't letting him believe that I could get him out, something that was frightening him so badly that it could blow him out of his skull before I could get him to the West.

This thing in my hand wasn't ticking, but Karasov was.

Get him out. Get him out now.

There was some string holding some empty sacks together in the corner of the barn and I cut off a length but it was rotten with age so I raked in the tool compartment of the truck and found some electric cable and used that, winding it round the grasshopper switch and putting the bomb on the floor under the front seat on the driver's side and chocking it with a bit of wood from the littered floor of the barn so that it couldn't roll about; a thing like that could come in handy. Then I connected the battery lead and started the engine and left it running to warm up while I fetched Karasov.

He was coming out of the cave when I got there. They'd heard the engine start.

'So you found your toy,' Volodarskiy said.

'Yes.' I sensed that he hadn't told Karasov what kind of toy it was: it would have pushed him right over the edge.

'Then I wish you a good journey.'

'Thank you.' I looked at Karasov. 'We're going.'

He moved his head slowly, like a punch-drunk, and stared at me in the cold light of the morning, and all I could see in his eyes was the knowledge of death. As I led him across the snow to the barn it occurred to me that his mind, at the brink of hysteria, might be open to the dark voices of premonition that I could not hear.