Nick Charles is asked to find a relative's husband; he and two others are murdered, but Nick gathers the suspects and names the murderer.
Nick Charles (William Powell) and his wife Nora (Myrna Loy) arrive on a train in San Francisco, trying to rest but finding a New Year's Eve party in their house and an invitation to Nora's relatives. Selma Landis (Elissa Landi) tells Nick her husband Robert has disappeared, and Aunt Katherine (Jessie Ralph) asks Nick to investigate. David Graham (James Stewart) brings Selma a bottle, and he tells Nick and Nora that Robert offered to leave if he would give him $25,000. Singer Polly Byrnes (Penny Singleton) argues with Steve Dancer (Joseph Calleia), who hits her. Dancer warns Phil Byrnes (Paul Fix) to stay away. Nick and Nora arrive at the club and see Robert Landis (Alan Marshall), who says he's not going back. Polly promises to go with Robert if he gets the $25,000. Polly sings, and Robert calls David. Polly leaves with Robert, who gets bonds from David. Robert goes home for his clothes, but Selma takes a gun and follows him. Robert is shot. David finds Polly with a gun and sends her home; he takes her gun and throws it in the river. Dancer returns to find Nick using his phone and suspecting him of shooting Robert.
Police Lt. Abrams (Sam Levene) questions Katherine's household, but Dr. Kammer (George Zucco) gave Selma a sedative. Nora tells Abrams to join Nick at the club. Selma tells Nora she did not kill Robert and asks her to tell David. Nora goes to David and sees Phil outside the window before she and David are arrested. Abrams questions Polly and Dancer, who is joined by his lawyer Floyd Casper. Abrams collects their guns. Nick says Phil has a gun and was hanging around. The lights go out, and Dancer escapes. Abrams has Polly arrested. Dancer goes to Phil, while Nick gets Nora out of jail. Selma tells David her gun was not fired, and she is arrested for murder.
A note is thrown through the Charles' kitchen window, but Nick has to get it away from their dog Asta. It says Phil is an ex-con and was married to Polly. Abrams shows Nick a check for $20,000 that Robert gave Polly, but Nick shows it was forged. Abrams has Polly arrested. Abrams and Nick find Phil strangled. Nick takes the key to Polly's apartment and finds a microphone in the room above. Dancer leaves Polly's and shoots at Nick. Nick finds the janitor's dead body, and Nora identifies him as her father's old gardener. Nick finds a ladder of pipes and tells Abrams to invite everyone. Abrams questions, and Nick explains and inquires also. He accuses David of killing all three. David admits he hated Robert and Selma and pulls a gun; but he is overpowered by police. Abrams arrests Dancer for forgery and trying to kill Nick. In the final scene on the train Nick notices that Nora is knitting baby socks.
This entertaining detective story combines wit and an intriguing plot. Nick is portrayed as a heavy drinker, but he definitely loves his wife.