“Which he was,” said Poirot. “Or rather, he thought he was. When Jennie handed him a glass of poisoned water, as agreed, he believed she would stay alive and do her best to ensure that Nancy was found guilty of the three Bloxham Hotel murders. He believed that she would speak to the police in such a way as to ensure that they suspected Nancy. He did not know that Nancy had arranged a cast-iron alibi with Lord and Lady Wallace! Or that, after his death, the cufflink would be pushed to the back of his mouth, the key hidden behind the tile, the window opened . . . He did not know that Jennie Hobbs, Nancy Ducane and Samuel Kidd would arrange it so that it appeared to the police that the killings must have taken place between a quarter past seven and ten minutes past eight!”

“No, Richard was not privy to those details,” Jennie agreed. “Now you can see why I described Nancy’s plan as brilliant, Monsieur Poirot.”

“She was a talented artist, mademoiselle. The best artists, they have the eye for detail and for structure: how all the components fit together.”

Jennie turned to me. “Neither Nancy nor I wanted any of this. You have to believe me, Mr. Catchpool. Richard would have killed me if I had resisted him.” She sighed. “We had it all worked out. Nancy was supposed to get off scot-free, and Sam and I were to be punished for trying to frame Nancy, but not by death. A short term of imprisonment would suffice, we hoped. After which we intended to marry.” Seeing our surprised faces, Jennie added, “Oh, I don’t love Sam as I loved Patrick, but I am very fond of him. He would have made a good companion if I had not ruined it all by stabbing Nancy.”

“It was already ruined, mademoiselle. I knew that you had murdered Harriet Sippel and Richard Negus.”

“I did not murder Richard, Monsieur Poirot. That’s one thing you’re wrong about. Richard wanted to die. I gave him the poison with his full consent.”

“Yes, but under false pretenses. Richard Negus agreed to die because you agreed to his plan that all four of you would die. Then it became five when you involved Nancy Ducane. But you did not really agree. You betrayed him and plotted behind his back. Who knows whether Richard Negus would have chosen to die at that moment and in that way if you had told him the truth of your secret pact with Nancy Ducane.”

Jennie’s expression hardened. “I did not murder Richard Negus. I killed him as an act of self-defense. He would have murdered me otherwise.”

“You said that he did not explicitly threaten this.”

“No—but I knew it. What do you think, Mr. Catchpool? Did I murder Richard Negus or not?”

“I don’t know,” I said, confused.

“Catchpool, mon ami, do not be absurd.”