Ellery Queen’s Mystery Magazine. Vol. 105, Nos. 3 & 4. Whole Nos. 640 & 641, March 1995

“Well,” said Hugo, “if you’re right, I agree that my first factor should be one, not seven. What about my other factors. Do you question them?”

“In mentioning twelve carriages you overlooked the fact that this man has always seated himself in the centre of the train, clearly in order to be as close as possible to the exit point on the platform when he leaves the train. I agree that he might choose either the fifth or the sixth carriage, so I’m prepared to allow you a second factor of two.”

“Thank you,” said Hugo. “But even if you’re right, two men on your selected train on every working day in the year — it’s still quite a substantial total, isn’t it?”

“That,” said Mr. Piggin, “is where you make your gravest error. I invited you to consider the mind of the killer. Lonely, methodical, introverted. Is it not clear that he would be a numerologist?”

“You’ve lost me.”

“A numerologist is a man who places such importance on numbers that he regulates his life by them. There are lucky and unlucky numbers. The unluckiest is, of course, thirteen. Some people carry it forward through the multiplication table and consider twenty-six, thirty-nine, fifty-two, and so on as equally unfortunate. I once had a client who believed so firmly in this that when I presented him with a bill for thirty-nine pounds he came round in person to protest. I could only pacify him by increasing it to forty pounds. On the other hand, there are lucky numbers. They are based on the number seven and all its multiples up to sixty-three, which was, historically, deemed to be the grand climacteric. A particularly lucky number in this series was twenty-one, additionally important as being the age of majority. The law on that point may have changed, but the number has never lost its supreme power. And clearly it rules this killer absolutely.”

“How do you mean, Piggy?”

“You haven’t seen it? Look at the dates he selected. November tenth, February nineteenth, June fifteenth, August thirteenth, October eleventh. Write them numerically: 10/11, 19/2, 15/6, 13/8, and 11/10. You see? The total, in every case, is twenty-one. The Osbaldistone attempt on January twentieth fits in also. One or two might have been a coincidence. Certainly not six. Quite impossible.”

Hugo, who was feeling breathless, said, “Good God!” and “You don’t really think.” And then, “And what about the one I was involved in. That was March eighteenth — 18/3.”

“Quite so,” said Mr. Piggin. “And it is significant in two ways. First, it means that it was unquestionably one of the sequence we have been discussing. I refuse to believe that chance could have dictated this particular date. Second, it means that your mafia acquaintances are quite wrong in supposing that the killing was anything to do with Umberto’s mission for them in this country. He simply happened to offer an ideal chance for the Knifeman, whose opportunities had been much diminished as men tended to travel in groups. But Umberto, who had been living in Italy, would have known nothing about all this. Indeed, if the mafia had thought about it, they must have realised that their rivals in the drug trade would have had no time to organise the attack. Umberto had arrived from Italy, unannounced, that same day. No, no. It is quite clear that the man the mafia should be pursuing is not a professional rival but the Knifeman himself.”

Hugo had started scribbling dates on a piece of paper. He said, “April seventeenth adds up to twenty-one. Why did nothing happen on that day?”

“Because it happens to have been a Sunday.”

“Oh. So it was. Well then, look here—”

“Yes?”

“The next one is May sixteenth.”

“Yes.”

“Which is next Monday.”

“Quite so.”

“And do you really think—”

“Either you accept the laws of mathematics or you reject them.”

“Then shouldn’t we tell someone.”

“Can you imagine explaining it to Chief Inspector Mayburgh?”

“Perhaps not,” said Hugo. “But we must do something.”

“Certainly. Next Monday we will catch the six-ten train to Colchester. I will occupy a seat in carriage number five. You will occupy one in carriage number six.”

Hugo said, “Oh!” rather feebly. And then, “I suppose it would be the logical way of doing it.”

His carriage, which had been crammed to start with, was emptying rapidly. Hugo’s mouth was dry and he had an uncomfortable feeling in the pit of his stomach. Although he kept telling himself that Mr. Piggin’s theory was moonshine, one corner of his mind concentrated obstinately on the idea of a knife: long, thin, sharp-edged, with a needle point.

Shenfield, Ingatestone.

He stole another look at the man occupying the far corner seat. A very ordinary man. The only thing that had attracted Hugo’s attention was his immobility. His evening paper was on the seat beside him, but he was making no attempt to read it. Nothing suspicious in that, surely?