The ABC killer sends more letters promising to spill blood. Hercule's past, integrity and identity come into question while he fights a rising tide of xenophobia.

With the ABC killer still on the loose, Hercule realises that only he holds the key to the murders. He faces a race against time to stop the bloodbath.

It's 1933, and an older and greyer Hercule Poirot receives letters threatening murder. When no-one listens to his appeals, the once great detective must take matters into his own hands.