Jost jerked his head back. “What… ?”

“You say you left the barracks at five-thirty. You call the cops at five past six. Schwanenwerder is three kilometres from the barracks. You are fit: you run every day. You do not dawdle: it is raining hard. Unless you suddenly developed a limp, you must have arrived at the lake quite some time before six. So there are — what? — twenty minutes out of thirty-five unaccounted for in your statement. What were you doing, Jost?”

The young man looked stricken. “Maybe I left the barracks later. Or maybe I did a couple of circuits of the running track there first…”

“ ‘Maybe, maybe…’ ” March shook his head sadly. These are facts that can be checked, and I warn you: it will go hard for you if I have to find out the truth and bring it to you, rather than the other way round. You are a homosexual, yes?”

“Herr Sturmbannfuhrer! For God’s sake …”

March put his hands on Jost’s shoulders. “I don’t care. Perhaps you run alone every morning so you can meet some fellow in the Grunewald for twenty minutes. That’s your business. It’s no crime in my book. All I’m interested in is the body. Did you see something? What did you really do?”

Jost shook his head. “Nothing. I swear.” Tears were welling in his wide, pale eyes.

“Very well.” March released him. “Wait downstairs. I’ll arrange transport to take you back to Schlachtensee.” He opened the door. “Remember what I said: better you tell me the truth now than I find it out for myself later.”

Jost hesitated, and for a moment March thought he might say something, but then he walked out into the corridor and was gone.

March rang down to the basement garage and ordered a car. He hung up and stared out of the grimy window at the wall opposite. The black brick glistened under the film of rainwater pouring down from the upper storeys.