Celebrated sleuth Hercule Poirot, now retired and living in self-imposed exile in Venice, reluctantly attends a Halloween séance at a decaying, haunted palazzo. When one of the guests is murdered, the detective is thrust into a sinister world of shadows and secrets. In post-World War II Venice, Poirot, now retired and living in his own exile, reluctantly attends a seance. But when one of the guests is murdered, it is up to the former detective to once again uncover the killer.