Adapted from Patrick Hamilton's play and similar to the 1940 Gaslight film, the niece of a murdered aunt marries a man who tries to make her insane to get her aunt's jewels.
Paula (Ingrid Bergman) gives up singing lessons because she is in love with Gregory Anton (Charles Boyer). They enjoy their honeymoon in Italy. Paula inherited 9 Thornton Square in London from her aunt, and they live there. Paula says her aunt was a singer and strangled, and Gregory plays her aunt's favorite song. Paula finds her aunt's letter from Sergis Bauer, and Gregory grabs it. Gregory hires Nancy (Angela Lansbury) as a maid and tells her not to talk to Paula. Gregory tells Paula that she is getting forgetful. They go to the Tower of London to see the crown jewels, and they run into Brian Cameron (Joseph Cotton). Paula loses a broach that Gregory gave her. Brian and Miss Thwaites (May Whitty) see Paula step out and go back in. Brian goes to Scotland Yard and examines the murder case, learning that jewels are missing.
Gregory cleverly controls Paula, who feels that Nancy despises her. Gregory has Miss Thwaites turned away but tells Paula they are going to the theater, making Paula so happy she sings. Then Gregory accuses her of hiding a picture and questions the servants Elizabeth (Barbara Everest) and Nancy. Paula finds the picture where she found it before, but Gregory says she is too ill for the theater. Paula says she is frightened when she is alone. Nancy flirts with Gregory. When Gregory is out working, Paula sees the gaslight dim.
Paula insists on going to Lady Dalroy's musical reception, and Gregory notices Brian. Gregory tells Paula his watch is gone, and he finds it in her purse. She denies taking it and cries. Gregory takes her home, and Brian follows. Gregory tells Paula that her mother was insane. When he goes out, Brian and the policeman Williams (Tom Stevenson) try to figure out where he went. Paula hears noises above her and asks Elizabeth about the gas. Williams tells Brian that he saw Gregory appear dusty. Brian tells Williams to take out Nancy. After Gregory goes out, Brian calls on Paula and walks past Elizabeth. Brian gives Paula her aunt's glove. He sees the gas go down, and she tells of her aunt's things upstairs. Gregory is searching the furniture up there. Brian looks for Gregory's gun, and Paula finds the letter from Bauer. Brian says it is Gregory's writing. Gregory finds his desk lock broken and questions Paula, who says a man did it. Brian comes in from upstairs. Gregory has a gun and struggles with Brian, who ties up Gregory and shows Paula the gems. Brian leaves Paula with Gregory, who asks her to help him. She mocks him by pretending she is mad. Gregory goes with the police, and Paula invites Brian to visit her.
This psychological thriller shows how insidious a manipulator
can be in an intimate relationship, but one wonders why someone
would be so cruel to get some jewels.