Someone at the Door is a British mystery play by Campbell Christie and Dorothy Christie which was first staged in 1935, and ran successfully in London's West End.
The play has been adapted twice into films. In 1936 Someone at the Door directed by Herbert Brenon and starring Aileen Marson and Billy Milton and in 1950 Someone at the Door directed by Francis Searle and starring Michael Medwin and Garry Marsh. It was also made into a 1939 television film for the BBC.