" Mr. Satterthwaite looked cheered.

Suddenly an idea struck him. His jaw fell.

"My goodness," he cried, "I've only just realized it! That rascal, with his poisoned cocktail! Anyone might have drunk it! It might have been me!"

"There is an even more terrible possibility that you have not considered," said Poirot.

"Eh?"

"It might have been me," said Hercule Poirot. "

― Agatha Christie , Three Act Tragedy (Hercule Poirot, #10)