Post World War II, retired Belgian detective Hercule Poirot (Kenneth Branagh) is living in Venice from his self-imposed exile. When approached by another detective to attend a séance and figure out its secrets, he reluctantly agrees. All is fine until a guest is murdered during the ritual, and Poirot must find who did it.

With a group of suspects, he has his work cut out for him, having to thin out the innocent from the guilty. Poirot finds himself with his most difficult case yet, as a sinister world of shadows and secrets lay in the dark of the haunted palazzo.