"But why?"
"My friend, Savaronoff was the second greatest chess player in the world. In all probability Number Four did not even know the rudiments of the game. Certainly he could not sustain the fiction of a match. He tried all he knew to avoid the contest. When that failed, Wilson's doom was sealed. At all costs he must be prevented from discovering that the great Savaronoff did not even know how to play chess. Wilson was fond of the Ruy Lopez opening, and was certain to use it. Number Four arranged for death to come with the third move, before any complications of defence set in."
"But, my dear Poirot," I persisted, "are we dealing with a lunatic? I quite follow your reasoning, and admit that you must be right, but to kill a man just to sustain his rôle! Surely there were simpler ways out of the difficulty than that? He could have said that his doctor forbade the strain of a match."
Poirot wrinkled his forehead.
"Certainement, Hastings," he said, "there were other ways, but none so convincing. Besides, you are assuming that to kill a man is a thing to avoid, are you not? Number Four's mind, it does not act that way. I put myself in his place, a thing impossible for you. I picture his thoughts. He enjoys himself as the professor at that match. I doubt not he has visited the chess tourneys to study his part. He sits and frowns in thought; he gives the impression that he is thinking great plans, and all the time he laughs in himself. He is aware that two moves are all that he knows—and all that he need know. Again, it would appeal to his mind to foresee the events and to make the man his own executioner at the exact time that suits Number Four.... Oh, yes, Hastings, I begin to understand our friend and his psychology."
I shrugged.
"Well, I suppose you're right, but I can't understand any one running a risk he could so easily avoid."
"Risk!" Poirot snorted. "Where then lay the risk? Would Japp have solved the problem? No; if Number Four had not made one small mistake he would have run no risk."
"And his mistake?" I asked, although I suspected the answer.
"Mon ami, he overlooked the little gray cells of Hercule Poirot."