Something fell behind him and clattered down the stairs. “There you are,” said the voice. “I’ll give in.”

The detective pulled himself to his feet, and groping forward felt an ankle. He moved up two or three steps and thrust his arm through the other’s arm. “I knew that you had common sense,” he declared amiably. “Half a moment till I strike a match. It’s as dark as the pit in here. We don’t want to break our necks.”

Together they emerged from the front door just as Moreland was thinking of organising a rescue party of one, and as the crash of glass behind them told of a smashed skylight.