Poirot smiled. “You wish me to encourage you to have confidence in me, since you have none in yourself? Mon ami, you know more than you are aware of knowing. Do you remember you made a joke, at the hotel, about all three victims arriving on Wednesday, the day before the murders? You said, ‘It’s almost as if they had an invitation to present themselves for slaughter, one that said, “Please come to the day before, so that Thursday can be devoted entirely to your getting murdered.’ ”

“Well, what about it?”

“Your joke relied on the idea that getting murdered is more than enough activity for one day—to travel across the country by train and get murdered on the same day, that would be too much for anyone! And the killer does not want his victims to have to exert themselves unduly! This is funny!”

Poirot smoothed his mustache, as if he imagined that laughing might have shaken it out of shape.

“Your words made me wonder, my friend: since getting murdered is really no effort for the victim, and since no killer is so considerate of those he intends to poison, why does he not kill the three victims on the Wednesday night?”

“He might have been busy on Wednesday night,” I said.

“Then why not arrange for the three victims to arrive at the hotel on Thursday morning and afternoon instead of Wednesday morning and afternoon? The killer would still have been able to kill them when he did, n’est-ce pas? On Thursday evening, between a quarter past seven and ten past eight?”

I did my best to look patient. “You’re overcomplicating things, Poirot. If the victims all knew each other, which we know they did, maybe they had a reason for all being in London for two nights, a reason that had nothing to do with the killer. He chose to kill them on the second night because it was more convenient for him. He didn’t invite them to the Bloxham; he simply knew that they would be there, and when. Also. . .” I stopped. “No, never mind. It’s silly.”

“Tell me the thing that is silly,” Poirot ordered.

“Well, it’s possible that if the murderer is a meticulous planner by nature, he would not plan the murders for the same day that he knew his victims would be traveling to London, in case their trains were delayed.”

“Perhaps the killer also had to travel to London, from Great Holling or somewhere else. It is possible that he—or she, for it might be a woman—did not want to make a long, tiring journey and commit three murders on the same day.”

“Even if that’s so, the victims could still have arrived on the Thursday, couldn’t they?”