'You know what the hurry is,' he said. 'One of your people in London is reporting regularly to the KGB. It's only a matter of time…'

'But you're special,' I said. 'You are kept apart from everything else we do.'

'They have a good source,' he said. 'It must be someone at the top in London.'

' London want you to stay on,' I said. 'For two years at least.'

' London is Oliver Twist. London always wants more. Is that why you came here? To tell me to stay on?'

'It's one of the reasons,' I admitted.

'You've wasted your time, Bernd. But it's good to see you, just the same.'

'They'll insist.'

'Insist?' While he considered the idea of London forcing him to stay on, he carefully tore the edging from a block of postage stamps. 'How can they insist on anything? If I ceased to report to them, what could they do about that? If they betrayed me, the word would soon get around and your whole service would suffer.'

'There would be no question of London betraying you. You know that.'

'So what sanction do they have? How could they insist?' Having made the postage stamps look more tidy, he rolled up the stamp edging to make it into a ball.

I said, 'You'd have to give up all thoughts of going to the West. And I think you want to go to the West.'

'My wife wants to go. She wants to see her brother's grave. He was killed in Tunisia in the war. They were very close as children. But if it proves impossible, then so be it.' He shrugged and unrolled the stamp edging, smoothing it flat again.

'And you want to see your son in São Paulo.'

He said nothing for a long time, toying with the stamp edging as if he were thinking of nothing else. 'You are still as painstaking as you used to be, Bernd. I should have guessed you'd trace the payments.'

'A holding company in Luxembourg that receives money from Bayerische Vereinsbank in Munich, and transfers money to the São Paulo office of the Banco Nacional is not exactly deep cover,' I said. 'That publishing-company account isn't active enough to fool anyone for long.'

'Who else knows that?' He opened the brass flap on his ornate pen stand and looked at the dried-up sediment in the inkwell.

'I have told no one.'

'I appreciate that, Bernd.'

'You got me out of Weimar,' I said.

'You were young. You needed help.'

He screwed up the stamp edging a second time and tossed it into the dry inkwell with commendable accuracy before closing the brass flap. They arrested Busch the very next day.'

'That was a long time ago.'

'I gave them his address.'

'I know.'

'Who could have guessed the poor old fellow would go back home again?'

'I would have done the same,' I said.

'Not you, Bernd. You're made of harder stuff.'

'That's why they sent me to tell you to hang on,' I said.

He didn't smile. Without looking up from his desk, he said, 'Suppose I could help you find the traitor in London?'

So that was it. So that's what all the messages and the difficulties had been leading up to. I said nothing. Munte knew nothing about London except the identity of Silas, who'd been his friend and run him so long ago. And nowadays Silas had little contact with the day-to-day running of London Central. Surely Silas couldn't be one of them.

He spoke again, still fidgeting with the pen stand. 'I couldn't name him, but I could identify him positively to your satisfaction. And provide evidence that would satisfy even a law court, if that's the course that London decided upon.'

Giles Trent, perhaps. I had to find out if he was trying to sell me something I already had. 'How would you do that? What sort of evidence?'

'Could you get me out?'

'You alone?'

'Me and my wife. Together. It would have to be the two of us together. We wouldn't be separated.'

I felt sure that he was going to tell me about Giles Trent. If the KGB had discovered that we were playing Trent, I'd like to know. But I couldn't pull Munte out just for that.

Perhaps he guessed the sort of thoughts that were running through my mind. 'I'm talking about someone with access to London Data Centre,' he said, staring at me, knowing that I would be surprised to hear he even knew such a place existed. 'Someone with pass-codes prefixed "Knee jerk".'

I sat very still and tried to look impassive. Now there was no longer any way of avoiding the awful truth. The 'Knee jerk' codes were used only by a handful of specially selected top personnel in London Central. Used in the Data Centre's computer, they accessed the automatic link – hence 'Knee jerk' – to CIA data files. If they'd seen printout with 'Knee jerk' marks here in East Berlin, there was no limit to what might have been betrayed. It was not Giles Trent we were talking about; it was someone senior, someone very close to Operations. 'How soon could you get this evidence?'

'This evening.'

'When would you want to travel?' This development changed everything. If Brahms Four could help identify such a well-placed Soviet agent, London would want him there to give evidence.

'You know what women are like, Bernd. My wife would probably need a few days to think about it.'

'Tomorrow. Ill take you back with me. But let me make this clear. Unless you produce irrefutable evidence that enables me to identify the person who is supplying this material, the deal is off.'

'I'll bring you four handwritten pages of data. Would that satisfy you?'

'Handwriting? Then it's certainly not genuine. No agent would be that stupid.'

'Is that what you think, Bernd? Sometimes – when it's late, and one is tired – it becomes very difficult to take all the necessary precautions. Blame the KGB controller in the London Embassy who forwarded the original instead of making a copy. Or blame the clerks here in Berlin who have left the document in the file, Bernd. I feel sorry for the agent. I know exactly how he felt.'

'Handwritten? And no one here remarked on it?'

'Lots of our papers are handwritten. We are not quite so automated as you are in the West. It's a distinctive hand – very neat with curly loops.'

'From London?' Fiona's writing. But could it all be a plant?

'We are only a bank. Our security precautions are not very elaborate. It was a very interesting and most secret report about proposed Bank of England support for sterling. I recognized what it was only because I was looking for such things.'

'By tonight, you say?'

'I know where the report is.'

'Your wife must understand that she can't take anything with her except what she can wear and put in her pockets.'

'We have talked about it many times, Bernd.'

'No friends or relatives, no small dogs or parrots or albums of family photos.'

'She understands,' he said.

'It doesn't get easier,' I said. 'Don't frighten her, but make sure your wife understands that she's risking her life.'

'She will not be frightened, Bernd.'

'Very well.'

'I will see you at nine o'clock, my friend. Can you find the Pioneer House at Wühlheide near Köpenick? It's a twenty-five-minute ride on the S-Bahn from here. Room G-341. I'll have the papers.'

'I'll find it.'

He stood up and, with both hands on his hips, tilted his head back and sighed like a man awakening from a long sleep. 'At last the decision is made,' he said. 'Can you think what that means to me, Bernd?'

'I'll need to phone my wife in London,' I said. 'She gets anxious if I don't keep in contact. Can I direct-dial on a secure phone?'

'Use this one. I call the West several times every day. Dial nine and then the number,' he said. 'There is no monitoring of calls, but it will be logged. Be discreet, Bernd.'

'We have a prearranged code,' I explained. 'Just domestic chat. I'll mention the handwritten paper. She'll understand what's happened.'