“Out of all of which,” said De Gollyer, “the interesting thing is that Rankin has supplied the reason why the supply of detective fiction is inexhaustible. It does all come down to the simplest terms. Seven possibilities, one answer. It is a formula, ludicrously simple, mechanical, and yet we will always pursue it to the end. The marvel is that writers should seek for any other formula when here is one so safe, that can never fail. Be George, I could start up a factory on it.” “The reason is,” said Rankin, “that the situation does constantly occur. It’s a situation that any of us might get into any time. As a matter of fact, now, I personally know two such occasions when I was of the party; and very uncomfortable it was too.” “What happened?” said Steingall. “Why, there is no story to it particularly. Once a mistake had been made, and the other time the real thief was detected by accident a year later. In both cases only one or two of us knew what had happened.” De Gollyer had a similar incident to recall. Steingall, after reflection, related another that had happened to a friend. “Of course, of course, my dear gentlemen,” said Quinny impatiently, for he had been silent too long, “you are glorifying commonplaces. Every crime, I tell you, expresses itself in the terms of the picture puzzle that you feed to your six-year-old. It’s only the variation that is interesting. Now quite the most remarkable turn of the complexities that can be developed is, of course, the well-known instance of the visitor at a club and the rare coin. Of course every one knows that? What?” Rankin smiled in a bored, superior way, but the others protested their ignorance. “Why, it’s very well known,” said Quinny lightly. “A distinguished visitor is brought into a club—dozen men, say, present, at dinner, long table. Conversation finally veers around to curiosities and relics. One of the members present then takes from his pocket what he announces as one of the rarest coins in existence—passes it around the table. Coin travels back and forth, every one examining it, and the conversation goes to another topic, say the influence of the automobile on domestic infelicity, or some other such asininely intellectual club topic—you know? All at once the owner calls for his coin. “The coin is nowhere to be found. Every one looks at every one else. First, they suspect a joke. Then it becomes serious—the coin is immensely valuable. Who has taken it?