Burgh Island, South Devon is one of the filming locations. The island is associated with writer Agatha Christie, who often visited and used the location as inspiration for at least two novels: And Then There Were None (1939) and Evil Under the Sun (1941). Previous Christie stories filmed there include: Miss Marple: Nemesis (1987) and Evil Under the Sun (2001).
Inspector Leach (Matthew Rhys) is an amalgamation of three characters from the book: Inspector James Leach (a local police officer), Superintendent Battle (Leach's uncle who is vacationing in the area), and Angus MacWhirter (a mysterious stranger who may be a witness).
Lady Tressilian actress Anjelica Huston's grandfather Walter Huston starred in another famous mystery from writer Agatha Christie: O Vingador Invisível (1945).
Jack Farthing previously appeared in the Agatha Christie adaptations of The Big Four (2013) and The ABC Murders (2018).