It was now that she remembered that her case had also happened to cost Bruno Stahlecker his life. She let her laughter subside, and fixing a more serious expression to her face she set about expressing her condolences. This also involved her cheque-book. For a moment I thought about saying something noble to do with the hazards of the profession, but then I thought of Bruno’s widow and let her finish writing it.

‘Very generous,’ I said. ‘I’ll see that this gets to his wife and family.’

‘Please do,’ she said. ‘And if there’s anything else that I can do for them, you will let me know, won’t you?’

I said that I would.

‘There is something you can do for me, Herr Gunther,’ she said. ‘There are still the letters I gave you. My son asked me if those last few could be returned to him.’

‘Yes, of course. I’d forgotten.’ But what was that she said? Was it possible that she meant the letters I still held in the file back at my office were the only surviving letters? Or did she mean that Reinhard Lange already had the rest? In which case, how had he come by them? Certainly I had failed to find any more of the letters when I searched Hering’s apartment. What had become of them?

‘I’ll drop them round myself,’ I said. ‘Thank goodness he has the rest of them back safely.’

‘Yes, isn’t it?’ she said.

So there it was. He did have them.

I began to move towards the door. ‘Well, I’d better be getting along, Frau Lange.’ I waved the two cheques in the air and then slipped them into my wallet. ‘Thanks for your generosity.’

‘Not at all.’

I frowned as if something had occurred to me.

‘There is one thing that puzzles me,’ I said. ‘Something I meant to ask you about. What interest does your company have in the Rolf Vogelmann Detective Agency?’

‘Rolf Vogelmann?’ she repeated uncomfortably.

‘Yes. You see I learnt quite by accident that the Lange Publishing Company has been funding an advertising campaign for Rolf Vogelmann since July of this year. I was merely wondering why you should have hired me when you might with more reason have hired him?’

Frau Lange blinked deliberately and shook her head.

‘I’m afraid that I have absolutely no idea.’

I shrugged and allowed myself a little smile. ‘Well, as I say, it just puzzled me, that’s all. Nothing important. Do you sign all the company cheques, Frau Lange? I mean, I just wondered if this might be something your son could have done on his own without informing you. Like buying that magazine you told me about. Now what was its name? Urania.’

Clearly embarrassed, Frau Lange’s face was beginning to redden. She swallowed hard before answering.