The film is adapted from Agatha Christie's novel "Halloween Murders". The story takes place in Venice after World War II. On a strange Halloween Eve, the retired famous detective Hercule Poirot (Kenneth Branagh) will live a quiet and comfortable life in Venice, the most charming city in the world. He is reluctantly invited to a dilapidated and gloomy palace to attend a party. When one of the guests is murdered, Poirot is drawn into a sinister world full of shadows and secrets.