Based on a play by Ladislas Fodor, a prominent couple is blackmailed while the husband prosecutes a murder his wife knows the accused did not commit.
At the Dearden's party Helen Dearden (Loretta Young) dances with Hugh Lewis (Henry Daniell), who asks her for 2,000 pounds because of letters from her husband Alan Dearden (Franchot Tone) to Diana Roggers. Alan hopes to become attorney general. Lewis instructs Helen to change two 1,000 pound notes and throw the money off a cliff at Dover. She hears a man warn his wife, gets the letters and burns them. Alan is recalled from their vacation for a murder case at Dover that Helen saw. In court Alan interrogates Samuel Metford (Dudley Digges), who says his wife fell by accident after he warned her; but the woman witness fails to come forward. Helen reads about the trial and tells Alan that Metford is innocent.
Alan gets a note from Diana and goes to see her. Lewis tells Diana (Aileen Pringle) to sell Alan letters for 5,000. Helen has Bunny Jeffers (Roland Young) take Alan's place at a baptism. Alan comes home with a cut hand. Helen tells Bunny her predicament, and she hears that Alan was seen on Malett Street where Diana lives. Bunny argues with Alan that Metford may be innocent, and questions Alan at length where he was during the baptism and reminds him he was seen on Malett Street. Scotland Yard's General Lawrence (Lewis Stone) learns that Diana was strangled at that time and that her memo had "A. D." on it. Police look in the trash for the letter Alan said he got. Lawrence looks at Alan's cut hand and tells him Diana was murdered. A bloody knife was found, and blood was on her neck. Alan claims that a man attacked him with a knife. Lawrence learns they found the letter to Alan in Diana's handwriting.
Bunny meets Helen, who says that Alan is seeing Diana. She plans to testify about Dover, and Bunny asks her to wait. Helen is given a subpoena, and the defense calls her. She testifies that she went to Dover and admits she changed the money and threw it off the cliff for Alan's letters. Her account clears Metford; but the judge asks her who the blackmailers are, and she names Diana. Lawrence comes in and arrests Alan for murder. Lawrence sees Diana's threatening letter to Alan, who admits he killed her in self-defense. Alan says she tried to kill someone she was expecting. Helen denies that Lewis was the blackmailer and finds him in her car. She asks Lewis to clear Alan and agrees to pay him. They go to Lawrence, and Lewis signs a statement that Diana threatened to kill him. Alan shows Lewis's cut hand and says he killed Diana. Alan only confessed to lead Lewis into a trap. Lewis pleads it was self-defense.
Although the surprise ending at first seems contrived because of the web of evidence against Alan, the actual result is more true to the characters. This drama shows how innocent persons can be made to look guilty by circumstantial evidence.