“You had a new servant girl: Dorcas. She is here with you today only because I asked you to bring her. She is important to this story. You told me that Dorcas had been with you for just a few days, and I saw for myself that she is a little clumsy. She brought me a cup of coffee and spilled most of it. Luckily not all was spilled, and so I was able to drink some. I immediately recognized it as the coffee made by Pleasant’s Coffee House. Their coffee is unmistakeable; there is no other like it, anywhere.”

“Blimey!” said Fee Spring.

“Indeed, mademoiselle. The effect upon my mind was profound: at once, I put together several things like pieces of a jigsaw that fit perfectly. The strong coffee, it is very good for the brain.” Poirot looked pointedly at Fee as he said this. She pursed her lips in disapproval.

“This not very capable maid—pardon me, Mademoiselle Dorcas, I am sure you will improve, given time—she was new! I put this fact together with the coffee from Pleasant’s, and it gave me an idea: what if Jennie Hobbs was Louisa Wallace’s maid, before Dorcas? I knew from the waitresses at Pleasant’s that Jennie used to go there often to collect things for her employer, who was a posh society lady. Jennie spoke of her as ‘Her Ladyship.’ It would be interesting, would it not, if Jennie, until a few days ago, worked for the woman providing Nancy Ducane’s alibi? An extraordinary coincidence—or not a coincidence at all! At first, my thoughts on this matter proceeded along an incorrect track. I thought, ‘Nancy Ducane and Louisa Wallace are friends who have conspired to kill la pauvre Jennie.’ ”

“What a suggestion!” said Louisa Wallace indignantly.

“A shocking lie!” her husband St. John agreed.

“Not a lie, pas du tout. A mistake. Jennie, as we see, is not dead. However, I was not mistaken to believe that she was a servant in the home of St. John and Louisa Wallace, replaced very recently by Mademoiselle Dorcas. After speaking to me at Pleasant’s on the night of the murders, Jennie had to leave the Wallaces’ house, and quickly. She knew that I would soon arrive there to ask for confirmation of Nancy Ducane’s alibi. If I had found her there, working for the woman providing that alibi, I would instantly have been suspicious. Catchpool, tell me—tell us all—what exactly would I have suspected?”

I took a deep breath, praying I hadn’t got this all wrong, and said, “You would have suspected that Jennie Hobbs and Nancy Ducane were colluding to deceive us.”