'Don't be upset,' Slavsky said as he peeled off his jacket, 'about the heat in here. The windows are sealed to keep the dirt out, and nothing can be done about it.'

People were moving along the corridor, heaving bags and packages, among them an English couple with their voices raised on the understanding that since the natives couldn't speak their language they couldn't be heard.

'But George, you'll have to look at things the way Clarence does. He says this is World Adventure Number One — that's exactly how he put it last night — World Adventure Number One. The Trans-Siberian Express.'

'Clarence is out of his bloody mind about bloody trains.'

A group of Chinese struggled past with little red-and-white flags sticking out of their knapsacks; then there were a few passengers on their own, and these I noted. One of them looked in and gave me an expressionless stare and lumbered on with his body angled under the weight of a black canvas bag. This was why I'd asked Croder not to put any support people on this train: if anyone took an interest in me I'd know they weren't Bureau.

'Did you bring some food?' Slavsky asked me.

'Yes.'

'And toilet paper? Rubber ball?'

'Yes.'

'Then you booked through a good travel agent.'

'Yes.'

'The main thing to remember,' he said, and then broke off and staggered suddenly as the floor jerked under our feet and the heavy steel couplings out there took up the slack and rang like a peal of bells under the huge roof of the station and the crowds lining the platform started calling and waving and holding children up and the passengers filling the corridors waved back, and I never came to know what the main thing to remember was, but I thought Slavsky would tell me sooner or later.

Through the windows of the corridor the hazy glow of the station gave way to a string of lights lining the track, and when the acceleration had evened out I told Slavsky I was going to stretch my legs, but he was buried in a book under the reading lamp and didn't look up.

People were going back into their compartments and leaving the corridors clear, but some girls in grey overalls with the state insignia on them were washing down the walls, and others were trundling vacuum cleaners in and out of the compartments nearer the dining car.

'How many carriages are there?' I asked an apple-faced woman with a mop.

'On this train? Twenty-two.'

'A lot of carriages.'

'A lot of work!'

I stepped over her grey galvanized bucket and went through the rubber-walled booth into the next carriage, taking my time, noting every face, looking into the compartments when the curtains were open, scanning the faces of the men who stood in the vestibules at the end of the carriages coughing in the clouds of smoke from their cigarettes. Twenty-two carriages, six hundred people, and I might have to walk the entire length of the train a dozen times, fifty times before I found him, Zymyanin. A lot of work, yes indeed, you were right, little mother.

He would know, Zymyanin, that the Bureau would have wanted to bring him to a second rendezvous with a second contact, because the information he'd got for us was still shut in his head. He would know that when he'd failed to signal London to set up a new rendezvous, Control would make it his business to put a watch on his movements and have the new contact standing by to force him into a meeting if he could. He would know that I was on this train.

'I'm sorry,' I said, 'babushka,' as I got in the way of her mop.

'I shouldn't be working as late as this!' A stainless steel tooth flashed in the bluish light. 'It was the snow, after St Petersburg, that held everything up!'

He wouldn't recognize me, Zymyanin, had never seen me before and would not have been given the photograph of a high-echelon shadow executive; but he would come to know me, come to know who I was, who I must be, when he noticed I was searching the train for someone. And once he'd got a fix on me I'd move immediately into a red sector, if that man had in fact set up a kill for Hornby in the freight yard in Bucharest and had now set one up for me.

That would be all right in the streets of a city or in open countryside where there was adequate cover: the risk would be calculated, the kind we thrive on if we play them right. But here in his long thin tube stretching through the wilderness there were risks Dependent on sheer chance, and at any given time Zymyanin could catch sight of me from the far end of a corridor before I saw him. Then he'd bring me under his surveillance, and I might not have enough time to realize it before he made his move.

The thing is, I'd asked Croder, is it worth the risk?

I was expecting your question. Yes, we believe it is.

It was the only excuse I'd got for taking it, the only justification. Croder's word.

When I came back to the compartment the night sky through the windows of the corridor was sable-black and jewelled with stars as the Rossiya ran through open country and the dark.

Slavsky was asleep, I think; he didn't say anything when I changed into the track suit we'd bought at the used-clothing shop this morning in Moscow, and stretched out on my bunk. The heating bad been turned off not long before midnight and now the air was cold, and tainted with the constant smell of disinfectant from the lavatories. I'd strip-washed half an hour ago, using the big iron bucket in the nearest toilet, the water rust-coloured and near freezing; but that hadn't been the main problem, which was to keep things from dropping through the big uncovered drainpipe onto Russian soil, artifacts for posterity. But the little black rubber ball had worked well enough in the handbasin, a stand-in for the missing plug. In the last five hours I had covered the whole length of the train three times, waiting in the queue for a late supper in the nearest dining car and surveilling for more than an hour and then moving on, using other passengers — Caucasian, and in groups when I could find them — as mobile cover, wandering with them along the rocking corridors and meeting with bands of gypsies, some Americans with the Stars and Stripes sewn proudly onto their jeans, a French army colonel in full uniform, a gang of Russian hooligans shouting the odds about the coming revolution, gaggles of winsome little ballet students on their way to the Academy of Dance in Novosibirsk, a Scottish Highlander in a Campbell clan kilt and a party of singing drunks.

I had also met our senior provodnik again, Galina, the muscled redhead, and chatted with her for a while before she signed off her shift, putting reasonably direct questions about working conditions on the train and especially the rate of pay, and expressing mild shock at its inadequacy considering the daunting responsibilities of her job. There was no excuse for crossing her palm with silver at this stage, but expectations were carefully stirred.

It wasn't that I felt the need for extra comforts of any sort, but for a recruitable agent-in-place with an unbreakable cover who could ferret out information for me that might indirectly further my progress in the mission or even protect my life — because there was a second possible scenario in my mind: Zymyanin might be perfectly reliable, a good agent understandably scared off by the Bucharest thing and unwilling to risk another rendezvous, in which case he was no danger to me. But if the opposition had tried to kill him off along with Hornby in that freight yard, they might have followed him onto the train, to try again.

Zymyanin's own life could be in hazard as the Rossiya plunged headlong through the night, and if I made contact with him it could be lethal. A thousand roubles in Galina's bank account to buy her secret services could prove a profitable investment, and to hell with that carping old crone in the counting house. We play our little games, we, the brave and diligent ferrets in the field, with wit and sinew as our weapons when we can, but if base money can provide the means of our salvation as we burrow through the dark and treacherous labyrinths then we will use it. We're not proud, my good friend, we are not proud: we find we live longer if we are practical.