London bank clerk William Marble (Charles Laughton) is deeply in debt. When his boss learns of a lawsuit for an overdue bill, he warns Marble that he will be dismissed if he cannot settle the matter quickly. Then, Marble is visited by a rich nephew whom he has not seen in many years, James Medland (Ray Milland). All night, Marble tries to borrow money from him, having received a financial tip that could solve all his financial troubles. However, Medland is not interested. Driven to desperation, Marble poisons his nephew and buries the body in the back yard.
With the dead man's money, Marble speculates on margin and makes Â£30,000, a large sum that enables him to retire. However, fear of his crime being discovered makes him consistently nervous and irritable. His wife Annie (Dorothy Peterson) knows something is wrong, but wrongly guesses he has embezzled from the bank. To relieve his nervous tension, he sends Annie and their daughter Winnie (Maureen O'Sullivan) away on a three-week vacation. While they are gone, he has an affair with Madame Collins (Verree Teasdale), a local shopowner. Winnie finds out when she returns a day early and discovers Collins in the house, but keeps quiet about it.
Despite their new financial wealth, troubles continue to grow for the Marble family. Annie finally figures out what her husband has done, but stands by him. Winnie becomes a bit of a snob, consorting with a higher social class of people and sneering at her parents. When she runs away one night, Annie chases after her in the rain and becomes very ill. However, under Marble's loving care, she begins to recover. Then Madame Collins shows up and blackmails Marble into giving her some money. Annie overhears and commits suicide with some of the same cyanide used to kill Medland. Marble is convicted for her murder. When Winnie visits on the day of his execution, Marble reassures her that he did not kill Annie, but says that he is nonetheless at peace with his fate. He is convinced he is paying a bill that was only deferred.
Who does Marble reassure that he did not kill Annie?
Winnie