Society sleuths Nick and Nora Charles investigate a murder aboard a floating casino. Nick and Nora Charles are attending a charity benefit aboard a gambling ship. After a murder occurs, suspicion falls on Phil Brant, who had argued with the victim earlier in the evening. When Phil and his wife seek help from Nick and Nora, Nick refuses to get involved. But when shots are fired outside his own apartment, Nick begins to investigate, and he soon finds himself in a confusing case with numerous suspects. Nick and Nora Charles were the ultimate screen couple, husband and wife detectives, always in step and never missing an opportunity to outwit one another as they solved each crime, which they did just in time for the movie's ending. Myrna Loy was a fantastic Nora, the ideal wife and considering she made 14 movies with William Powell, she made it look like they were really married. The Thin Man movies, all six of them, played more like sophisticated screwball comedies than murder mysteries, and their comic banter enhanced the proceedings. Their little wire-haired terrier, Asta, quite often stole the scene as he helped sleuth out the guilty party. He was a great little actor and rumor had it that away from the Thin Man movies, Asta was really Skippy. However, the six Thin Man movies credit this cute pooch as "Asta."

Freedonia国家财政陷入困难，有钱的寡妇Mrs. Teasdale（玛格丽特·杜蒙 Margaret Dumont 饰）推荐Rufus T. Firefly （格劳乔·马克斯 Groucho Marx 饰）出任国家领袖，她才答应出资资助国家。Freedonia的邻国Sylvania想要对其发起进攻，Sylvania的大使Trentino于是派出了两名间谍Chicolini（奇科·马克斯 Chico Marx饰）和Pinky（哈勃·马克斯 Harpo Marx饰）去刺探Firefly的情报。然而这两个不专业的间谍却闹出了不少笑话。Firefly的秘书Bob Roland （泽伯·马克斯 Zeppo Marx 饰）让Firefly多加小心，然而昏庸的Firefly并没有放在心上，随着他和大使Trentino的矛盾越来越大，战争终于无可避免.....