“It was then that an idea came to me. There was an assurance—a slickness about the crime. I had no doubt that in the future Patrick Redfern would repeat his crime. What about the past? It was remotely possible that this was not his first killing. The method employed, strangulation, was in harmony with his nature—a killer for pleasure as well as for profit. If he was already a murderer I was sure that he would have used the same means. I asked Inspector Colgate for a list of women victims of strangulation. The result filled me with joy. The death of Nellie Parson found strangled in a lonely copse might or might not be Patrick Redfern’s work—it might merely have suggested choice of locality to him, but in Alice Corrigan’s death I found exactly what I was looking for. In essence the same method. Juggling with time—a murder committed not, as is the usual way, before it is supposed to have happened, but afterwards. A body supposedly discovered at a quarter past four. A husband with an alibi up to twenty-five past four.

“What really happened? It was said that Edward Corrigan arrived at the Pine Ridge, found his wife not there, and went out and walked up and down. Actually, of course, he ran full speed to the rendezvous, Caesar’s Grove (which you will remember was quite nearby), killed her and returned to the café. The girl hiker who reported the crime was a most respectable young lady, games mistress in a well-known girls’ school. Apparently she had no connection with Edward Corrigan. She had to walk some way to report the death. The police surgeon only examined the body at a quarter to six. As in this case the time of death was accepted without question.

“I made one final test. I must know definitely if Mrs. Redfern was a liar. I arranged our little excursion to Dartmoor. If anyone has a bad head for heights, they are never comfortable crossing a narrow bridge over running water. Miss Brewster, a genuine sufferer, showed giddiness. But Christine Redfern, unconcerned, ran across without a qualm. It was a small point, but it was a definite test. If she had told one unnecessary lie—then all the other lies were possible. In the meantime Colgate had got the photograph identified by the Surrey Police. I played my hand in the only way I thought likely to succeed. Having lulled Patrick Redfern into security, I turned on him and did my utmost to make him lose his self-control. The knowledge that he had been identified with Corrigan caused him to lose his head completely.”

Hercule Poirot stroked his throat reminiscently.

“What I did,” he said with importance, “was exceedingly dangerous—but I do not regret it. I succeeded! I did not suffer in vain.”

There was a moment’s silence. Then Mrs. Gardener gave a deep sigh.