"Why?"
Poirot put his hand into his pocket and pulled out—a white bishop.
"Why," I cried, "you forgot to give it back to Dr. Savaronoff."
"You are in error, my friend. That bishop still reposes in my left-hand pocket. I took its fellow from the box of chessmen Mademoiselle Daviloff kindly permitted me to examine. The plural of one bishop is two bishops."
He sounded the final "s" with a great hiss. I was completely mystified.
"But why did you take it?"
"Parbleu, I wanted to see if they were exactly alike."
He stood them on the table side by side.
"Well, they are, of course," I said, "exactly alike."
Poirot looked at them with his head on one side.