There was undoubtedly something to be said for Poirot’s view. I asked him when he had made up his mind definitely upon the point.

“That is just it. I am not sure. I cannot be sure. Mon ami , I would give anything to know . Let me but place Number Two definitely as Abe Ryland, and we draw nearer to our goal.”

“He has just arrived in London, I see by this,” I said, tapping the letter. “Shall you call upon him, and make your apologies in person?”

“I might do so.”

Two days later, Poirot returned to our rooms in a state of boundless excitement. He grasped me by both hands in his most impulsive manner.