I retired crestfallen, and observed Poirot grinning at me. He thanked the steward, a note changed hands, and we took our departure.

“It’s all very well,” I remarked heatedly, “but that last answer must have damped your precious theory, grin as you please!”

“As usual, you see nothing, Hastings. That last answer is, on the contrary, the coping-stone of my theory.”

I flung up my hands in despair.

“I give it up.”

When we were in the train, speeding towards London, Poirot wrote busily for a few minutes, sealing up the result in an envelope.

“This is for the good Inspector McNeil. We will leave it at Scotland Yard in passing, and then to the Rendezvous Restaurant, where I have asked Miss Esmée Farquhar to do us the honour of dining with us.”