They plodded on, working out lines to take in the endless interviews. They correlated, sorted and discussed each fragment of information. ‘Finding the pattern of the case,’ Alleyn called it. A five minutes’ walk brought them to Sling Street and to a large block of rather pretentious service flats. They took the lift up to 110 and rang the bell.

‘I’m going to take some risks here,’ said Alleyn.

The door was opened by Captain Withers himself.

He said: ‘Good morning. Want to see me?’

‘Good morning, sir,’ said Alleyn. ‘Yes. You had our message just now, I hope. May we come in?’

‘Certainly,’ said Withers and walked away from the door with his hands in his pockets.

Alleyn and Fox went in. They found themselves in a mass-production furnished sitting-room with a divan bed against one wall, three uniform armchairs, a desk, a table and built-in cupboards. It had started off by being an almost exact replica of all the other ‘bachelor flats’ in Grandison Mansions, but since it is impossible to live in any place without leaving some print of yourself upon it, this room bore the impress of Captain Maurice Withers. It smelt of hairwash, cigars and whisky. On one wall hung a framed photograph of the sort advertised in magazines as ‘artistic studio studies from the nude.’ On the bookshelves guides to the Turf stood between shabby copies of novels Captain Withers had bought on the Riviera and, for some reason, troubled to smuggle into England. On a table by the divan bed were three or four medical text-books. ‘Donald Potter’s,’ thought Alleyn. Through a half-open door Alleyn caught a glimpse of a small bedroom and a second masterpiece that may have been a studio study but appeared to be an exercise in pornographic photography.

Captain Withers caught Fox’s bland gaze directed at this picture and shut the bedroom door.

‘Have a drink?’ he said.

‘No, thank you,’ said Alleyn.

‘Well, sit down then.’