Shadows on the Stairs (1941).

Frank Vosper

In Shadows on the Stairs, a London boardinghouse is the site of murder. The basis for the film is the play "Murder on the Second Floor" by actor-playwright Frank Vosper (The Man Who Knew Too Much; adaptation of Agatha Christie's "Philomel Cottage" as Love from a Stranger). He died at age 37 in 1937 when he fell from the liner Paris after a party. The death was ruled accidental.