“There,” he said. “That is all my business.”

“What were you doing there?” I asked, in lively curiosity.

“I left something to be analysed.”

“Yes, but what?”

“The sample of cocoa I took from the saucepan in the bedroom.”

“But that has already been tested!” I cried, stupefied. “ Dr. Bauerstein had it tested, and you yourself laughed at the possibility of there being strychnine in it.”

“I know Dr. Bauerstein had it tested,” replied Poirot quietly.

“Well, then?”