Just for a moment Katherine fancied that Poirot looked disappointed.
“He is a great admirer of yours, M. Poirot,” she said, and she related some of the things that Knighton had said. It amused her to see the little man plume himself like a bird, thrusting out his chest, and assuming an air of mock modesty that would have deceived no one.
“That reminds me, Mademoiselle,” he said suddenly, “I have a little matter of business I have to speak to you about. When you were sitting talking to that poor lady in the train, I think you must have dropped a cigarette case.”
Katherine looked rather astonished. “I don’t think so,” she said. Poirot drew from his pocket a cigarette case of soft blue leather, with the initial K on it in gold.
“No, that is not mine,” Katherine said.
“Ah, a thousand apologies. It was doubtless Madame’s own. K , of course, stands for Kettering. We were doubtful, because she had another cigarette case in her bag, and it seemed odd that she should have two.” He turned to Derek suddenly. “You do not know, I suppose, whether this was your wife’s case or not?”
Derek seemed momentarily taken aback. He stammered a little in his reply: “I—I don’t know. I suppose so.”
“It is not yours by any chance?”
“Certainly not. If it were mine it would hardly have been in my wife’s possession.”
Poirot looked more ingenuous and childlike than ever.
“I thought perhaps you might have dropped it when you were in your wife’s compartment,” he explained guilelessly.