'There he is, near the bar,' said Werner, holding open the door so we could look across the crowded dance floor. There was a crush around the tables where two men in chef's whites dispensed a dozen different sorts of sausages and foaming tankards of strong beer. Emerging from the scrum with food and drink was the man who was to be detained.

'I hope like hell we've got this right,' I said. The man was not just a run-of-the-mill bureaucrat; he was the private secretary to a senior member of the Bonn parliament.

I said, 'If he digs his heels in and denies everything, I'm not sure we'll be able to make it stick.'

I looked at the suspect carefully, trying to guess how he'd take it. He was a small man with crew-cut hair and a neat Vandyke beard. There was something uniquely German about that combination. Even amongst the over-dressed Berlin social set his appearance was flashy. His jacket had wide silk-faced lapels, and silk also edged his jacket, cuffs and trouser seams. The ends of his bow tie were tucked under his collar and he wore a black silk handkerchief in his top pocket.

'He looks much younger than thirty-two, doesn't he?' said Werner.

'You can't rely on those computer printouts, especially with listed civil servants or even members of the Bundestag. They were all put onto the computer when it was installed, by copy typists working long hours of overtime to make a bit of spare cash.'

'What do you think?' said Werner.

'I don't like the look of him,' I said.

'He's guilty,' said Werner. He had no more information than I did, but he was trying to reassure me.

'But the uncorroborated word of a defector such as Stinnes won't cut much ice in an open court, even if London will let Stinnes go into a court. If this fellow's boss stands by him and they both scream blue murder, he might get away with it.'

'When do we take him, Bernie?'

'Maybe his contact will come here,' I said. It was an excuse for delay.

'He'd have to be a real beginner, Bernie. Just one look at this place – lit up like a Christmas tree, cops outside, and no room to move – no one with any experience would risk coming into a place like this.'

'Perhaps they won't be expecting problems,' I said optimistically.

' Moscow know Stinnes is missing and they've had plenty of time to alert their networks. And anyone with experience will smell this stakeout when they park outside.'

'He didn't smell it,' I said, nodding to our crew-cut man as he swigged at his beer and engaged a fellow guest in conversation.

' Moscow can't send a source like him away to their training school,' said Werner. 'But that's why you can be quite certain that his contact will be Moscow-trained: and that means wary. You might as well arrest him now.'

'We say nothing; we arrest no one,' I told him once again. 'German security are doing this one; he's simply being detained for questioning. We stand by and see how it goes.'

'Let me do it, Bernie.' Werner Volkmann was a Berliner by birth. I'd come to school here as a young child, my German was just as authentic as his, but because I was English, Werner was determined to hang on to the conceit that his German was in some magic way more authentic than mine. I suppose I would feel the same way about any German who spoke perfect London-accented English, so I didn't argue about it.

'I don't want him to know any non-German service is involved. If he tumbles to who we are, he'll know Stinnes is in London.'

'They know already, Bernie. They must know where he is by now.'

'Stinnes has got enough troubles without a KGB hit squad searching for him.'

Werner was looking at the dancers and smiling to himself as if at some secret joke, the way people sometimes do when they've had too much to drink. His face was still tanned from his tune in Mexico and his teeth were white and perfect. He looked almost handsome despite the lumpy fit of his suit. 'It's like a Hollywood movie,' he said.

'Yes,' I said. The budget's too big for television.' The ballroom was crowded with elegant couples, all wearing the sort of clothes that would have looked all right for a ball at the turn of the century. And the guests weren't the desiccated old fogies I was expecting to see at this fiftieth birthday party for a manufacturer of dishwashers. There were plenty of richly clad young people whirling to the music of another time in another town. Kaiserstadt – isn't that what Vienna was called at a time when there was only one Emperor in Europe and only one capital for him?

It was the makeup and the hair-dos that sounded the jarring note of modernity, that and the gun I could see bulging under Werner's beautiful silk jacket. I suppose that's what was making it so tight across the chest.

The white-coated waiter returned with another big tray of glasses. Some of the glasses were not empty. There was the sudden smell of alcohol as he tipped cherries, olives, and abandoned drinks into the warm water of the sink before putting the glasses into the service lift. Then he turned to Werner and said respectfully, 'They've arrested the contact, sir. Went to the car just as you said.' He wiped the empty tray with a cloth.

'What's all this, Werner?' I said.

The waiter looked at me and then at Werner and, when Werner nodded assent, said, 'The contact went to the suspect's parked car… a woman at least forty years old, maybe older. She had a key that fitted the car door. She unlocked the glove compartment and took an envelope. We've taken her into custody but the envelope has not yet been opened. The captain wants to know if he should take the woman back to the office or hold her here in the panel truck for you to talk to.'

The music stopped and the dancers applauded. Somewhere on the far side of the ballroom a man was heard singing an old country song. He stopped, embarrassed, and there was laughter.

'Has she given a Berlin address?'

'Kreuzberg. An apartment house near the Landwehr Canal.'

'Tell your captain to take the woman to the apartment. Search it and hold her there. Phone here to confirm that she's given the correct address and we'll come along later to talk to her,' I said. 'Don't let her make any phone calls. Make sure the envelope remains unopened; we know what's in it. I'll want it as evidence, so don't let everybody maul it about.'

'Yes, sir,' said the waiter and departed, picking his way across the dance floor as the dancers walked off it.

'Why didn't you tell me he was one of our people?' I asked Werner.

Werner giggled. 'You should have seen your face.'

'You're drunk, Werner,' I said.

'You didn't even recognize a plainclothes cop. What's happening to you, Bernie?'

'I should have guessed. They always have them clearing away the dirty dishes; a cop doesn't know enough about food and wine to serve anything.'

'You didn't think it was worth watching his car, did you?'

He was beginning to irritate me. I said, 'If I had your kind of money, I wouldn't be dragging around with a lot of cops and security men.'

'What would you be doing?'

'With money? If I didn't have the kids, I'd find some little pension in Tuscany, somewhere not too far from the beach.'

'Admit it; you didn't think it was worth watching his car, did you?'

'You're a genius.'

'No need for sarcasm,' said Werner. 'You've got him now. Without me you would have ended up with egg on your face.' He burped very softly, holding a hand over his mouth.

'Yes, Werner,' I said.

'Let's go and arrest the bastard… I had a feeling about that car – the way he locked the doors and then looked round like someone might be waiting there.' There had always been a didactic side to Werner; he should have been a school-teacher, as his mother wanted.

'You're a drunken fool, Werner,' I said.

'Shall I go and arrest him?'