More than a century old, these grim-looking apartment blocks, five and six storeys high, had been built to shelter peasants who came to the city looking for jobs in the factories. They had changed very little. Rolf Mauser lived on the second floor in a rambling, tumbledown apartment building in Prenzlauer Berg. He was bleary-eyed and barefoot when he opened the door, a red silk dressing gown over his pyjamas.

'What the hell are you doing here?' he said as he took the chain off the door. It was his turn to be surprised in the middle of the night, and I rather relished it.

He motioned me into the sitting room and I sank down on a soft chair without removing either coat or hat. 'A change of plan, Rolf,' I said. 'I had a feeling that it wasn't good on the street tonight.'

'It's never good on the street,' he said. 'Do you want a bed?'

'Is there room for me?'

'Rooms are all I have in abundance. You can take your choice of three different ones.' He put a bottle of Polish vodka on the table alongside me and then opened the white porcelain stove to poke the ashes over. 'The rents over this side of the Wall are more or less the same, whether you've got a two-room flat or a huge house. So why move?' The acrid smell of burning coal filled the room.

'I wondered whether you'd be here, Rolf.'

'Why not? After what happened in London, this is the safest place, isn't it?'

'How do you figure that, Rolf?' I said.

'The evidence will be in London. That's where they'll be looking for the culprit.'

'I hope so, Rolf,' I said.

'I had to do it, Bernd. I had to bring him round the corner, you know. That man in London was going to blow the whole network.'

'Let's forget it,' I said, but Mauser was determined to have my approval for his deed.

'He'd already told Berlin KGB to have personnel and solitary prison accommodation ready for up to fifty arrests. The Brahms network would have been kaputtgemacht. And several other networks too. Now do you understand why I had to do what I did?'

'I understand it, Rolf. I understand it even better than you do.' I poured myself a shot of Rolfs fruit-flavoured vodka and drank it down. It was too fiery for the fruit flavouring to soften it much.

'I had to execute him, Bernd.'

'Um die Ecke bringen – that's gangster talk, Rolf. Let's face the truth. You murdered him.'

'I assassinated him.'

'Only public officials can be assassinated; and even then the victims have to be tyrants. Executions are part of a process of law. Face it: you murdered him.'

'You play with words. It's easy to be clever now that the danger has been removed.'

'He was a weak and foolish man, riven by guilt and fear. He knew nothing of importance. He'd never heard of Berlin System until last week.'

'Yes,' said Rolf. 'Berlin System – that's what he promised them. I asked Werner about it. He said that it was a complete breakdown of all networks and contacts, including emergency contacts and inter service contacts, for the whole Berlin area. We were very worried, Bernd.'

'Where did you get Trent 's name and address?' I asked.

He didn't answer.

'From Werner. Who got it from that bloody Zena. Right?'

'You were asking Frank Harrington questions about some mix-up in 1978. Frank guessed that this man Trent was being investigated.'

'And he told Zena?'

'You know Zena. She got it out of him.'

'How many times do I have to tell you that Werner is not employed by the Department. Why didn't you get in touch with Olympia Stadion?'

'Not enough time, Bernd. And Werner is more reliable than your people at Olympia. That's why you use him, isn't it?'

'Why didn't you tell me what you were going to do that night in London?'

'We didn't want London Central to know,' said Rolf. He poured himself a shot of vodka. He was beginning to sweat, and it wasn't with the heat from the stove.

'Why not?'

'So where was this man Trent getting his Berlin System from? Answer me that. He was going to get it from someone in London, Bernd.'

'Damn right,' I said angrily. 'He was going to get it from me.' I looked at him, wondering how much to confide to him.

'From you, Bernd? Never.'

'It was all part of a play, you fool. I told him to promise it to Moscow. I promised him the System because I wanted to keep him on the hook while I reeled him in.'

'It was an official play, you mean?'

'You bloody fool, Rolf.'

'I killed the poor bastard for nothing?'

'You messed up my plan, Rolf.'

'Oh, my God, Bernd.'

'You'd better show me where I'm to sleep, Rolf. I have a busy day tomorrow.'

He stood up and mopped the sweat from his brow with a red handkerchief. 'I won't get to sleep, Bernd. It's a terrible thing I have done. How can I sleep with that on my conscience?'

Think of all the poor bastards you killed in those artillery bombardments, Rolf, and add one.'

22

The next morning was very sunny. Even Prenzlauer Berg looked good. But Rolf Mauser's second-floor apartment faced out onto a cobbled courtyard almost entirely filled by a large soot-caked chestnut tree. The greenish light reflected from its young leaves made it seem as if the whole place was under water.

Only a few stunted bushes grew in the yard. But there were bicycles there by the dozen and prams double-parked. Rows of rubbish bins too, their contents distributed far and wide by hungry cats that woke me in the night with their angry screeches. The narrow peeling stucco walls of the courtyard, which had brought the chestnut into early bud, echoed every sound. Everyone could hear the admonitions, arguments and shouted greetings of two women who were throwing pailfuls of water onto the mess and scrubbing energetically with stiff brooms.

'It's not exactly the Kaiserhof in its heyday,' said Rolf, serving himself from a dented pot of coffee and leaving me to do the same. He had the bluff manner of a soldier, the self-centred ways of a man who'd lived alone too long. 'Those damned cats kept me awake.'

'Cobbler's Boys,' I said, picking up one of the triangular wholemeal rolls that Berliners eat at breakfast time. 'I slept very well. Thanks for the bed, Rolf. I'll push on today.'

'It's difficult to get them now,' said Rolf. 'All bread prices are controlled. None of these lazy swines of bakers want the extra work of making anything but ordinary bread.' He'd recovered from his self-doubts of the night before, as all soldiers must renew their conscience with every dawn.

'It's the same everywhere,' I said.

'Stay a week if you want to. I get a bit fed up being here alone. The couple who let me share it are away visiting their married daughter.' He took his cup of coffee from the tray he'd brought, put milk into it, and sat down on the bed while I finished shaving. 'But you'll have to take your turn carrying coal from the cellar.'

'I hope I won't need a week, Rolf.'

'You're going to see Brahms Four?'

'Probably.'

'Is there really a person called Brahms Four?'

'I hope so, Rolf.'

'I always thought it was the code name for a syndicate. Why else would the Brahms Four material always be kept separate from everything else we sent?'

'Nothing so unusual about that.'

'Officially he's in the Brahms network.' He paused to let me know he was about to say something significant. 'But no one hi the Brahms network has ever seen him.'

'How do you know that?' I said sharply. 'Damn it, Rolf, you should know better than to discuss named agents with third parties.'

'Even if the third parties are also agents?'

'Especially then, because the chances of them being interrogated are that much greater.'

'You've been a long time away, Bernd. You've been sitting behind a desk in London too long. Now you talk like one of those memos that Frank Harrington likes to write.'