I could not help agreeing with a smile. I was still smiling as I reentered the room.

“ Eh bien! ” said Poirot immediately. “You make fun of Papa Poirot, is it not so?” He shook his finger at me. “You do not trust his grey cells? Ah, do not be confused! Let us discuss this little problem⁠—incomplete as yet, I admit, but already showing one or two points of interest.”

“The lake!” I said significantly.

“And even more than the lake, the boathouse!”

I looked sidewise at Poirot. He was smiling in his most inscrutable fashion. I felt that, for the moment, it would be quite useless to question him further.

We heard nothing of Japp until the following evening, when he walked in about nine o’clock. I saw at once by his expression that he was bursting with news of some kind.