After his exuberant performance as master of ceremonies in the dining room, Poirot had lapsed once more into quiet gloom. “You’re fretting about Jennie again, aren’t you?” I asked him.

He admitted that he was. “I do not want to hear that she has been found with a cufflink in her mouth, with the monogram PIJ. That is the news I dread.”

“Since there is nothing you can do about Jennie for the time being, I suggest you think about something else,” I advised.

“How practical you are, Catchpool. Very well. Let us think about teacups.”

“Teacups?”

“Yes. What do you make of them?”

After some consideration, I said, “I believe I have no opinions whatever on the subject of teacups.”

Poirot made an impatient noise. “Three teacups are brought to Ida Gransbury’s room by the waiter Rafal Bobak. Three teacups for three people, as one would expect. But when the bodies of the three are found, there are only two teacups in the room.”

“The other one is in Harriet Sippel’s room with Harriet Sippel’s dead body,” I said.

“Exactement. And this is most curious, is it not? Did Mrs. Sippel carry her teacup and saucer back to her room before or after the poison was put into it? In either scenario, who would carry a cup of tea along a hotel corridor, and then take it into a lift or walk down two flights of stairs with it in their hands? Either it is full and there is a risk of spillage, or it is half full or almost empty, and hardly worth transporting. Usually one drinks a cup of tea in the room in which one pours the cup of tea, n’est-ce pas?”

“Usually, yes. This killer strikes me as being as far from usual as it’s possible to be,” I said with some vehemence.

“And his victims? Are they not ordinary people? What about their behavior? Do you ask me to believe that Harriet Sippel carries her tea down to her room, sits in a chair to drink it, and then almost immediately the murderer knocks on her door and finds an opportunity to put cyanide in her drink? And Richard Negus, remember, has also left Ida Gransbury’s room for some unknown reason, but he arranges to be back in his own room soon afterward, with a glass of sherry that nobody at the hotel gave him.”

“I suppose when you put it like that . . .” I said.