But, on the other hand, this murder, followed so closely by the mysterious death of his other acquaintance, Colburn, had made a great impression upon him. He had thought and talked of little else, and, as it happened, he had known every detail. He had seen the knife with which James Tovey had been killed; he, in common with very few others, had known of the receipt of the marked counters. Suppose that the crimes had had such a powerful effect upon his imagination that he had felt an irresistible impulse to imitate them? Such things were known, were in fact a commonplace of the criminal psychologists.

Upon this assumption, the rest was easy. Mr. Copperdock had learnt by some accident that this man Richard Pargent would arrive at Paddington at 4:55 on Saturday, and had selected him as a likely victim. His imitative faculty fully developed, he had sent him the numbered counter, and had purchased a knife similar to the one which he had already seen. Then, just before the train was due, he had left his shop, met his victim, committed the crime, had a drink to steady his nerves, and then come home.