William Gridley, a newly arrived American diplomat at the
American Embassy in London, rents a room in the
Mayfair townhouse of Carly Hardwicke, a charming young woman and a fellow American expatriate. When Gridley inquires about Carly's marital status, she replies that she is separated and is unaware of her husband's whereabouts. Later, Gridley tells his superior, Franklyn Ambruster, that he has rented a room from Carly. Her name sounds familiar to Ambruster, so he calls the research department for information on her. Gridley and Carly go out on a date at a restaurant, where he is unaware that several patrons are staring and whispering about her. After they leave the restaurant, a mysterious man approaches Carly and she talks privately with him. The next day at the Embassy, Ambruster informs Gridley that Carly is suspected of murdering her husband Miles, but since his body has not been found, she cannot be prosecuted.
Scotland Yard Inspector Oliphant tells Gridley that Carly tried to collect on Miles'
life insurance a few weeks earlier. Determined to prove Carly's innocence, Gridley agrees to spy on her. Returning to the townhouse, Gridley finds a suspicious note on the floor and inspects Carly's room, where he discovers some books about murder and a gun in her bedside table. When Carly unexpectedly returns home, Gridley hides in her closet and overhears her talking to someone on the phone about an unspecified task that needs to be done that night. That evening, as Gridley and Carly are having a barbeque in the backyard while all the next-door neighbors are watching them from their windows, Carly's awning accidentally catches fire. After the fire makes the front page of national newspapers, Ambruster decides to transfer Gridley out of England to avoid further scandal, until Carly arrives at the Embassy to intercede on Gridley's behalf. Ambruster is immediately charmed by Carly, and after he takes her to lunch, he agrees with Gridley that Carly is innocent. The two men resolve to work together to clear her name. That night, they arrive outside the townhouse to see the mysterious man who spoke to Carly outside the restaurant leaving. Gridley follows him while Ambruster follows Carly, who leaves the townhouse shortly afterwards. Gridley learns that the mysterious man is a
minister and that Carly has sold him her
organ because she is strapped for money. When Gridley returns to the townhouse, Carly asks him to leave, having packed his bags. He insists he does not care if she murdered her husband and tells her that he loves her. Gridley calls Oliphant to inform him that he will not spy on Carly anymore. During their conversation, a gunshot is heard. Gridley rushes to Carly's room to find her standing over Miles' body with a gun in her hand. At her trial, Carly recounts on the stand that Miles sneaked into her room and admitted to setting her up for his murder. He had stolen valuable jewels, and had been faking his death since killing the assassin who was sent after him. Carly and Miles were struggling for his gun when it went off. At the
coroner's inquest, Carly is exonerated when Agatha Brown, a private nurse for Carly's crippled next-door neighbor, Mrs. Dunhill, testifies that she witnessed Carly struggling with Miles before she killed him in self-defense. After the inquest, Gridley overhears Mrs. Brown attempting to blackmail Carly for a pawn ticket to a candelabra that Miles used to stash the stolen jewels in. Carly realizes that it was actually Mrs. Dunhill who saw her kill Miles, not Mrs. Brown. Gridley and Carly try to retrieve the candelabra but find the pawnbroker murdered. They then locate Mrs. Brown in a
Penzance seaside resort, where they catch her pushing Mrs. Dunhill's wheelchair down a cliff edge to silence her. Gridley saves Mrs. Dunhill while Carly knocks Mrs. Brown out, just as Ambruster and Oliphant arrive by helicopter. Ambruster reassigns Gridley to the United States, and Carly is going with him. ==Cast==