A charity benefit sponsored by David Thayer is staged aboard the S.S. Fortune, Phil Brant's gambling ship. The entertainment is provided by a jazz band led by Tommy Drake and featuring singer Fran Page and talented but unstable clarinetist Buddy Hollis.
After a set, Drake informs a displeased Brant that he is quitting, having gotten a much better booking through Mitchell Talbin. However, Drake has a problem; he owes gangster Al Amboy $12,000. When Amboy (who is at the party) hears the news, he demands full payment that very night. Drake begs Talbin to give him an advance, but Talbin is unwilling to part with such a large sum. In desperation, Drake sneaks into Brant's office and opens the safe. However, he is shot from behind and killed.
Brant and socialite Janet Thayer elope, since her father David disapproves of Brant's lower-class background. The next morning, they show up at Nick and Nora Charles's apartment, having learned that Brant is the prime suspect in the murder. When a bullet narrowly misses Brant, Nick turns him in to the police, having decided it is safer for all concerned. Then Nick starts investigating.
Sneaking aboard the Fortune, Nick discovers on the back side of a sheet of music a receipt signed by Amboy acknowledging that Drake's debt had been paid. Nick then runs into Drake's band, allowed back on board to collect their instruments. When he questions them, he learns that the bandleader had many enemies, among them Buddy Hollis. Musician Clarence "Clinker" Krause agrees to help Nick track Buddy down, but they have no luck.
Nick and Nora visit a hostile Janet. The bullet that killed Drake likely came from an antique gun, and Nick knows Janet's father is an avid collector. Sure enough, he finds one gun missing from Mr. Thayer's collection. Janet leaves after getting a telephone call. Nick and Nora follow her to Fran's apartment. There they find Fran's body; she was stabbed in the back very recently. Janet claims Fran called to sell her some information, but that she got there after Fran was killed.
Nick finds a matchbook from a hotel in Poughkeepsie. That eventually leads him to a rest home where Buddy is undergoing treatment. The musician is too badly shaken up to answer Nick's questions, though Nora's presence seems to calm him down. When Nora sneaks back later by herself, Buddy becomes agitated, confesses to the murder, pulls out the antique gun, and tries to shoot Nora. Fortunately, he misses. Nick does not believe the deranged man's confession; Drake was slain by a well-aimed shot.
Nick decides to gather all the suspects together by arranging a party on the reopened Fortune and announcing that Buddy has fully recovered and will reveal the real murderer's identity that night. It is Nora who notices the vital clue. Amboy's wife shows up wearing a valuable necklace that matches the earrings of Mitchell Talbin's wife Phyllis. Sometime later, the necklace mysteriously reappears on Phyllis's neck. When Nick confronts Mitchell, Phyllis reveals that it was she who paid off her lover Drake's debt using the necklace. As Nick prompts Buddy to finger the killer, Mitchell finally confesses to both killings and pulls out a gun. An enraged Phyllis shoots him first, but her husband is only wounded. Then, despite Nick's pleas, she fires again and again, finishing the job.William Powell as Nick Charles
Myrna Loy as Nora Charles
Keenan Wynn as Clarence "Clinker" Krause
Dean Stockwell as Nick Charles Jr.
Phillip Reed as Tommy Edlon Drake (as Philip Reed)
Patricia Morison as Phyllis Talbin
Leon Ames as Mitchell Talbin
Gloria Grahame as Fran Ledue Page (singing voice was dubbed by Carol Arden)
Jayne Meadows as Janet Thayar
Ralph Morgan as David I. Thayar
Bess Flowers as Jessica Thayar
Don Taylor as Buddy Hollis
Warner Anderson as Dr. Monolaw
Bruce Cowling as Phil Orval Brant
Connie Gilchrist as Bertha, the Charles' housekeeper
Henry Nemo as The Neem
William Bishop as Al Amboy
Marie Windsor as Helen Amboy
James Burke as Captain Callahan
This Thin Man movie differs in several respects from the others in the series, and was one of two films in the series not directed by W. S. Van Dyke, who died in 1943. The script was one of three not written by the husband and wife team of Albert Hackett and Frances Goodrich, who had worked with Dashiell Hammett to develop the Nick and Nora characters earlier in the series.
According to MGM records the film earned $1,403,000 in the US and Canada and $902,000 elsewhere, resulting in a loss of $128,000.