“If I were writing a story,” I said lightly, “I should weave this in with your latest idiosyncrasy and call it The Mystery of the Big Four .” I tapped the pencilled figures as I spoke.

And then I started, for our invalid, roused suddenly from his stupor, sat up in his chair and said clearly and distinctly:

“Li Chang Yen.”

He had the look of a man suddenly awakened from sleep. Poirot made a sign to me not to speak. The man went on. He spoke in a clear, high voice, and something in his enunciation made me feel that he was quoting from some written report or lecture.