“You did not understand that he believed Mademoiselle Cynthia guilty of the crime?”

“No,” I exclaimed, astonished. “Impossible!”

“Not at all. I myself nearly had the same idea. It was in my mind when I asked Mr. Wells that first question about the will. Then there were the bromide powders which she had made up, and her clever male impersonations, as Dorcas recounted them to us. There was really more evidence against her than anyone else.”

“You are joking, Poirot!”

“No. Shall I tell you what made Monsieur Lawrence turn so pale when he first entered his mother’s room on the fatal night? It was because, whilst his mother lay there, obviously poisoned, he saw, over your shoulder, that the door into Mademoiselle Cynthia’s room was unbolted.”

“But he declared that he saw it bolted!” I cried.