Sir Kenneth Branagh worked with the technical department to cause surprises for the cast. The actors were not warned about lights going out suddenly, or gusts of wind and slamming doors on the sets in which they worked, causing genuine confused and startled reactions from the actors to appear in the film. Kelly Reilly confirmed that filming the seance scene was a terrifying experience saying in an interview, "It scared the bejesus out of me."
The screenplay is inspired by Dame Agatha Christie's 1969 novel "Hallowe'en Party", with the setting changed from the UK to Venice, Italy. This is not the first time that Hallowe'en Party was adapted to film. In July of 2011, ITV Studios and WGBH released an 89-minute feature length film adaptation, Hallowe'en Party (2010), starring David Suchet as Poirot.
Hildur Guðnadóttir agreed to compose the film's score partly because her mother was an avid reader of Dame Agatha Christie.