‘I know he did.’ Inge followed me into the bedroom where I put on a shirt, and watched me as I fumbled with the cuff-link on the arm that I had grazed, and that she had bandaged. ‘You know,’ I said, ‘last night posed just as many questions as it answered. There’s no logic to anything, none at all. It’s like trying to make up a jigsaw, with not one but two sets of pieces. There were two things stolen from the Pfarrs’ safe; some jewels and some papers. But they don’t seem to fit together at all. And then there are the pieces which have a picture of a murder on them, which can’t be made to fit with those belonging to the theft.’

Inge blinked slowly like a clever cat, and looked at me with the sort of expression that makes a man feel meschugge for not having thought of it first. Irritating to watch, but when she spoke I realized just how stupid I really was.

‘Perhaps there never was just one jigsaw,’ she said. ‘Perhaps you’ve been trying to put one together when there were two all along.’ It took a moment or two to let that one sink all the way in, helped at the end with the flat of my hand smacking against my forehead.

‘Shit, of course.’ Her remark had the force of revelation. It wasn’t one crime I was staring in the face, trying to understand. It was two.

We parked on Nollendorfplatz in the shadow of the S-Bahn. Overhead, a train thundered across the bridge with a noise that possessed the whole square. It was loud; but it wasn’t enough to disturb the soot from the great factory chimneys of Tempelhof and Neukölln that caked the walls of the buildings which ringed the square, buildings which had seen many better days. Walking westwards into lower-middle-class Schöneberg, we found the five-storey block of apartments on Nollendorfstrasse where Marlene Sahm lived, and climbed up to the fourth floor.

The young man who opened the door to us was in uniform - some special company of SA that I failed to recognize. I asked him if Fraulein Sahm lived there and he replied that she did and that he was her brother.

‘And who are you?’ I handed him my card and asked if I might speak to his sister. He looked more than a little put out at the intrusion and I wondered if he had been lying when he said that she was his sister. He ran his hand through a large head of straw-coloured hair, and glanced back over his shoulder before standing aside.