Cast a Dark Shadow is a 1955 British suspense film directed by Lewis Gilbert. The black-and-white film was based on the play Murder Mistaken by Janet Green about a Bluebeard played by Dirk Bogarde.
After a year of marriage, Edward "Teddy" Bare (Dirk Bogarde) kills his wealthy older wife, Monica (Mona Washbourne), after she asks her lawyer, Phillip Mortimer (Robert Flemyng), to make a will. He stages it to look as if she was accidentally asphyxiated while drunkenly trying to light a gas heater.
To his chagrin, he discovers that she actually intended to leave him all her money; instead, he only inherits the mansion from a prior will, while her millions are left in trust to her only relative, her sister Dora. Edward will receive the money if Dora dies. An inquest rules it an accident, but Phillip makes it clear he suspects Edward. When Edward asks where Dora lives, Phillip tells him she is too far away, in Jamaica.
Edward manages to marry lower-class but well-off widow Freda Jeffries (Margaret Lockwood). She is more her husband's age, and much less trusting than her predecessor, keeping tight control of her fortune. As the death of a second spouse so soon after the first would be highly suspicious, he is powerless to do anything.