Now they were in a café on Munich’s Promenadeplatz, where the windows had been replaced with planks of wood. Ulrich looked carefully around before he spoke.

‘He called me.’

‘When?’

‘Just before I left Frankfurt – and after I got word that someone was looking for him.’

‘Did he say where he was?’

‘Here in Munich, but he didn’t say where. He admitted he was having trouble with a man called Emil, but I don’t think he’s aware people are searching for him. I told him to lay low and meet me in two days at a grocery shop I know on Türkenstrasse, near the Wittelsbach Palace – the owner’s husband was a comrade. In the meantime…’

‘…we need to find who’s asking about him!’

It didn’t take them long.

They put the word out that someone who knew the whereabouts of das Frettchen and was most interested in the reward would be at a bar on Ludwig Strasse opposite St Ludwig’s church at eight o’clock the following evening.

Sure enough, the man turned up. His German was good, but he clearly wasn’t a native speaker. And his story about das Frettchen owing him money was less than convincing. When Ulrich asked him where they’d met and for other details, he seemed hesitant. Ulrich, worried that they might be scaring him off, asked about the reward instead.

It turned out to be a generous one, and they agreed he’d pay half now and half when he found the man, which would be very soon, as Ulrich assured him das Frettchen was living just round the corner.

That was when it all went drastically wrong for Captain Christopher Stephens. He’d arranged for the American military police sergeant and two of his men to be waiting outside in civilian dress and in a German car. His plan had been for them to go with him to arrest the Ferret. But Ulrich insisted he leave with him through the rear of the bar, where he found himself in a small yard. Two men held him against the wall while an older man stood in front of him and asked him who he was and what he wanted.

Stephens’ only hope was that the Americans had realised what was going on and would come to look for him – he had said something to the sergeant about giving him ten minutes, and more than ten minutes had passed. He tried to buy time by saying that maybe there’d been a misunderstanding, and he wasn’t sure what the fuss was all about – he’d known the man called das Frettchen in Paris and they’d become friends; in fact – he gave a conspiratorial wink – they’d worked together in Avenue Foch. He owed his friend some money and had heard he was in Munich and wished to repay it; that was all.

‘I thought you told me he owed you money?’

Stephens realised he was shaking violently, and his mouth had turned dry.

‘You’re not German.’