Bruno shrugged. ‘The man is gold-plated. So what?’

‘Gold-plated, but not exactly treasured. He isn’t very popular with his staff. I found out the name of someone who he sacked and who might be the type to bear him a grudge.’

‘It’s not much of a reason, is it? Being sacked?’

‘According to my nurse, Marianne, it was common knowledge that he got the push for stealing drugs from the clinic dispensary. That he was probably selling them on the street. So he wasn’t exactly the Salvation Army type, was he?’

‘This fellow have a name?’

I thought hard for a moment, and then produced my notebook from my pocket. ‘It’s all right,’ I said, ‘I wrote it down.’

‘A detective with a crippled memory. That’s just great.’

‘Slow your blood down, I’ve got it. His name is Klaus Hering.’

‘I’ll see if the Alex has anything on him.’ He picked up the telephone and made the call. It only took a couple of minutes. We paid a bull fifty marks a month for the service. But Klaus Hering was clean.

‘So where is the money supposed to go?’

He handed me the anonymous note which Frau Lange had received the previous day and which had prompted Bruno to telephone me at the clinic.

‘The lady’s chauffeur brought it round here himself,’ he explained, as I read over the blackmailer’s latest composition of threats and instructions. ‘A thousand marks to be placed in a Gerson carrier-bag and left in a wastepaper basket outside the Chicken House at the Zoo, this afternoon.’

I glanced out of the window. It was another warm day, and without a doubt there would be plenty of people at the Zoo.

‘It’s a good place,’ I said. ‘He’ll be hard to spot and even harder to tail. There are, as far as I remember, four exits to the Zoo.’ I found a map of Berlin in my drawer and spread it out on the desk. Bruno came and stood over my shoulder.

‘So how do we play it?’ he asked.

‘You handle the drop, I’ll play the sightseer.’

‘Want me to wait by one of the exits afterwards?’

‘You’ve got a four-to-one chance. Which way would you choose?’

He studied the map for a minute and then pointed to the canal exit. ‘Lichtenstein Bridge. I’d have a car waiting on the other side in Rauch Strasse.’

‘Then you’d better have a car there yourself.’

‘How long do I wait? I mean, the Zoo’s open until nine o’clock at night, for Christ’s sake.’

‘The Aquarium exit shuts at six, so my guess is that he’ll show up before then, if only to keep his options open. If you haven’t seen us by then, go home and wait for my call.’