It’s 1933, and an older and greyer Hercule Poirot has fallen out of the public eye. When he receives anonymous letters threatening murder, he must take matters into his own hands.
Despite being warned off the case by Inspector Crome, Poirot continues to conduct his own investigation into the ABC killer. He receives another letter promising a murder in Churston and deciphers that the potential victim must be someone from his past. When national interest in the crimes begins to explode, the public turns against the Belgian sleuth, bringing his integrity into question.