“What?” Poirot caught me violently by the shoulders. “Was Dr. Bauerstein here on Tuesday evening? Here? And you never told me? Why did you not tell me? Why? Why?”

He appeared to be in an absolute frenzy.

“My dear Poirot,” I expostulated, “I never thought it would interest you. I didn’t know it was of any importance.”

“Importance? It is of the first importance! So Dr. Bauerstein was here on Tuesday night⁠—the night of the murder. Hastings, do you not see? That alters everything⁠—everything!”

I had never seen him so upset. Loosening his hold of me, he mechanically straightened a pair of candlesticks, still murmuring to himself: “Yes, that alters everything⁠—everything.”

Suddenly he seemed to come to a decision.