For a moment Mr. Ludgrove made no reply. When at length he spoke it was with a deep note of earnestness in his voice. “I am honoured by your confidence, Inspector. As you have guessed, I have been very much concerned by these murders. I have feared that they would be traced to one or other of my clients, some of whom, I regret to say, have little respect for the law. I know much of the inner history of Praed Street and its neighbourhood, and I regret to say that much of it is almost incredibly sordid. I refer of course to its underworld, and not to its respectable inhabitants, who are greatly in the majority. But of two facts I can assure you. The first is that in all my experience I have never heard of a crime committed by any of the class to which I refer except for some specific purpose, either gain or revenge, and the second is that none of them would resort to murder except perhaps in a sudden access of passion.”

The Inspector nodded. “That’s very much my own experience of regular crooks,” he replied. “But you say you’ve thought a lot about this business. Haven’t you any theory of your own?”