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."
Filmed on location in Venice. Kenneth Branagh wanted to use as many physical sets possible for filming.
Dr. Farrier mentions that medical staff accidentally killed the starving concentration camp prisoners they had liberated with milk. This is actually possible, and is caused by a condition known as "Refeeding Syndrome."
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.
Poirot suggests that Leopold should read Dickens. In Murder on the Orient Express (2017) Poirot is seen reading 'A Tale of Two Cities' and in Death on the Nile (2022) he reads "The Mystery of Edwin Drood"- the latter being the author's final novel, an unfinished murder mystery not revealing the killer's identity because of Dickens' untimely death, something which would most definitely intrigue Poirot in deducing for himself.