Ariadne Oliver (Zoë Wanamaker, Harry Potter) returns to join forces with Poirot to investigate a drowning at a Hallowe’en Party.

Ariadne Oliver (Zoë Wanamaker, Harry Potter) returns to join forces with Poirot to investigate a drowning at a Hallowe’en Party. As they look further, they uncover a series of mysterious deaths in the village. Are they connected? Adapted by Mark Gatiss (Sherlock).

This episode airs as part of MASTERPIECE MYSTERY! "Poirot XI."