“When was the crime committed?” asked Poirot.

“The body was discovered this morning about nine o’clock. Madame Renauld’s evidence, and that of the doctors goes to show that the death must have occurred about 2 a.m. But enter, I pray of you.”

We had arrived at the steps which led up to the front door of the Villa. In the hall another sergent de ville was sitting. He rose at sight of the commissary.

“Where is M. Hautet now?” inquired the latter.

“In the salon, monsieur.”

M. Bex opened a door to the left of the hall, and we passed in. M. Hautet and his clerk were sitting at a big round table. They looked up as we entered. The commissary introduced us, and explained our presence.

M. Hautet, the Juge d’Instruction, was a tall, gaunt man, with piercing dark eyes, and a neatly cut grey beard, which he had a habit of caressing as he talked. Standing by the mantelpiece was an elderly man, with slightly stooping shoulders, who was introduced to us as Dr. Durand.

“Most extraordinary,” remarked M. Hautet, as the commissary finished speaking. “You have the letter here, monsieur?”

Poirot handed it to him, and the magistrate read it.

“H’m. He speaks of a secret. What a pity he was not more explicit. We are much indebted to you, M. Poirot. I hope you will do us the honour of assisting us in our investigations. Or are you obliged to return to London?”