Poirot hung up the receiver and came back to me.

“Do you really think that necessary, Poirot?” I asked.

“It may be. There is no doubt that we are watched, you and I, and since that is so, they will soon know with whom we were lunching today. And it is possible that Number Four will scent danger.”

About twenty minutes later the telephone bell rang. I answered it. A curt voice spoke into the phone.

“Is that Mr. Poirot? St. James’s Hospital speaking. A young woman was brought in ten minutes ago. Street accident. Miss Flossie Monro. She is asking very urgently for Mr. Poirot. But he must come at once. She can’t possibly last long.”

I repeated the words to Poirot. His face went white.