“In fact, Thomas Brignell has never met this man before, but he remembers the name from when he gave the real Richard Negus his room key. Here, suddenly, is a man speaking to him in a confident, friendly and knowledgeable fashion and calling himself by that same name. Thomas Brignell assumes that he must be Richard Negus. He does not recall his face, but he blames only himself for this lapse.”

Thomas Brignell’s face had turned as red as claret.

Poirot went on, “The man impersonating Richard Negus asked for a glass of sherry. Why? To extend his encounter with Brignell a little, thereby imprinting it more strongly on the clerk’s memory? To soothe agitated nerves with some liquor? Maybe for both of these reasons.

“Now, if you will permit me a small digression: in the remains of this glass of sherry, the poison cyanide was found, as it was in Harriet Sippel’s and Ida Gransbury’s cups of tea. But it was not the tea or the sherry that killed the three murder victims. It cannot have been. These beverages arrived too late to kill, long after the murders had been committed. The sherry glass and the two teacups on the occasional tables next to the three bodies—they were essential for the staging of the crime scenes, to give the false impression that the killings must have occurred after a quarter past seven. In fact, the cyanide that killed Harriet Sippel, Ida Gransbury and Richard Negus was given to them much earlier and by another means. There is a water glass by the basin in each room of the hotel, is there not, Signor Lazzari?”

“Si, Monsieur Poirot. Yes, there is.”

“Then I expect that is how the poison was consumed: in water. The glass, in each case, was then carefully washed and replaced by the basin. Mr. Brignell,” Poirot addressed him unexpectedly, causing the assistant clerk to duck in his seat as if someone had taken a shot at him. “You do not like to speak in public, but you plucked up the courage to do so the first time we all gathered in this room. You told us of your encounter with Mr. Negus in the corridor, but you did not mention the sherry, even though I had specifically asked about it. Later, you sought me out and added the detail about the sherry to your story. When I asked you why you did not originally mention it, you gave me no answer. I did not understand why, but my friend here, Catchpool—he said something most perceptive and illuminating. He said that you are a conscientious man who would only withhold information in a murder enquiry if it caused you great personal embarrassment, and if you were sure it had nothing to do with the murder case. He hit upon the head of the nail with this assessment, did he not?”

Brignell gave a small nod.