“The police, as you are aware, have rather lost interest in you and me. The discovery of the knife in Mr. Copperdock’s coat pocket seems finally to have convinced them that the secret died with him, and, whatever the secret might have been, no further murders were to be anticipated. Detectives are busy people, they have no time to spare for academic research. I am sure that they are convinced that no actual danger menaces either Dr. Priestley or Mr. Ludgrove, although both of them are known to have received numbered counters. They were not likely to interfere with my schemes.