I left my flashlight in my coat pocket. A man with a torch in his hand at night needs only to paint a few coloured circles on his chest to make a better target of himself. And anyway, there was more than enough moonlight shining through what was left of the roof for me to see where I was going. Still, as I stepped through the north vestibule, into what had once been a waiting-room, I worked the Mauser’s slide noisily to let whoever was expecting me know that I was armed. And in the eerie, echoing silence, it sounded louder than a troop of Prussian cavalry.

‘You won’t need that,’ said a voice from the galleried floor above me.

‘All the same, I’ll just hang on to it awhile. There might be rats about.’

The man laughed scornfully. ‘The rats left here a long time ago.’ A torch beam shone in my face. ‘Come on up, Gunther.’

‘Seems like I should know your voice,’ I said, starting up the stairs.

‘I’m the same way. Sometimes I recognize my voice, but I just don’t seem to know the man using it. There’s nothing unusual in that, is there? Not these days.’ I took out my flashlight and pointed it at the man I now saw retreating into the room ahead of me.

‘I’m interested to hear it. I’d like to hear you say that sort of thing over at Prinz Albrecht Strasse.’ He laughed again.

‘So you do recognize me after all.’

I caught up with him beside a great marble statue of the Emperor Wilhelm I that stood in the centre of a great, octagonally-shaped hall, where my torch finally picked out his features. There was something cosmopolitan about these, although he spoke with a Berlin accent. Some might even have said that he looked more than a little Jewish, if the size of his nose was anything to go by. This dominated the centre of his face like the arm on a sundial, and tugged the upper lip into a thin sneer of a smile. His greying, fair hair he wore closely cropped, which had the effect of accentuating the height of his forehead. It was a cunning, wily sort of face, and suited him perfectly.

‘Surprised?’ he said.

‘That the head of Berlin’s Criminal Police should send me an anonymous note? No, that happens to me all the time.’

‘Would you have come if I had signed it?’

‘Probably not.’

‘And if I had suggested that you come to Prinz Albrecht Strasse instead of this place? Admit you were curious.’

‘Since when has Kripo had to rely on suggestion to get people down to headquarters?’

‘You’ve got a point.’ His smirk broadening, Arthur Nebe produced a hip flask from his coat pocket. ‘Drink?’