“Imbecile that I have been!” he cried. ‘“Triple imbecile! Not again will I vaunt my little grey cells!”

“That’s a good job at any rate,” I said grumpily. “But what is this all about?”

As usual, when following out his own ideas. Poirot paid absolutely no attention to me.

“The tradesmen’s books — I have left them entirely out of account! Yes, but where? Where? Never mind, I cannot be mistaken. We must return at once.”

Easier said than done. We managed to get a slow train to Exeter, and there Poirot hired a car. We arrived back at Crabtree Manor in the small hours of the morning. I pass over the bewilderment of the Bakers when we had at last aroused them. Paying no attention to anybody, Poirot strode at once to the study.

“I have been, not a triple imbecile, but thirty-six times one, my friend,” he deigned to remark. “Now, behold!”

Going straight to the desk he drew out the key, and detached the envelope from it. I stared at him stupidly. How could he possibly hope to find a big will-farm in that tiny envelope? With great care he cut open the envelope, laying it out flat. Then he lighted the fire and held the plain inside surface of the envelope to the flame. In a few minutes faint characters began to appear.

“Look, mon ami!” cried Poirot in triumph.

I looked. There were just a few lines of faint writing stating briefly that he left everything to his niece, Violet Marsh. It was dated Morch 25, 12.30 p.m, and witnessed by Albert Pike, confectioner, and Jessie Pike, married woman.

“But is it legal?” I gasped.

“As far as I know, there is no law against writing your will in a blend of disappearing and sympathetic ink. The intention of the testator is clear, and the beneficiary is his only living relation. But the cleverness of him! He foresaw every step that a searcher would take — that I, miserable imbecile, took. He gets two will-farms, makes the servants sign twice, then sallies out with his will written on the inside of a dirty envelope and a fountain-pen containing his little ink mixture. On some excuse he gets the confectioner and his wife to sign their names under his own signature, then he ties it to the key of his desk and chuckles to himself. If his niece sees through his little ruse, she will have justified her choice of life and elaborate education, and be thoroughly welcome to his money.”

“She didn’t see through it, did she?” I said slowly. “It seems rather unfair. The old man really won.”

“But no, Hastings. It is your wits that go astray. Miss Marsh proved the astuteness of her wits and the value of the higher education for women by at once putting the matter in my hands. Always employ the expert. She has amply proved her right to the money.”

I wonder — I very much wonder — what old Andrew Marsh would have thought!