In this adaptation of Victor Herbert's operetta a French princess flees an unwanted marriage by joining contracted brides going to New Orleans, where she meets a mercenary captain.
Princess Marietta (Jeanette MacDonald) won't marry Don Carlos and sings "Chansonette" with people. Don Carlos calls on her with her uncle (Douglass Dumbrille), who tells her the marriage bans are published. Marietta refuses, and her uncle says she could lose her land in exile. The maid Julie (Cecilia Parker) tells Marietta that she is going to New Orleans to marry, because she is too poor to marry Giovanni. A reward is offered for the fugitive Marietta as she in a disguise boards a ship going to America. Julie marries Giovanni, and the uncle realizes Marietta took her place. The women are contracted to be married; but pirates take over the ship by force.
"Tramp, Tramp, Tramp" announces the arrival of mercenary soldiers in fur caps. They attack and drive away the pirates. Marietta asks Captain Richard Warrington (Nelson Eddy) to take the women to New Orleans. He asks for petticoats to use as bandages. Around the campfire men sing "The Owl and the Bobcat." Warrington asks why Marietta is there. Warrington has no wife and says he likes it that way. He then sings "Neath the Southern Moon" to Marietta. People welcome the young women. Governor Gaspar d'Annard (Frank Morgan) thanks Warrington, while Madame d'Annard (Elsa Lanchester) restrains her husband. At the convent men meet the women. Marietta says that her credentials are false, telling the Governor that her conduct was not "above reproach." She is arrested and gives money to a poor couple. Warrington takes custody of Marietta and rents a house for her. She refuses to cook but shows him she can sing. When three men call, Marietta runs out.
The Governor gives Warrington a month's salary for his men and tries to send them away while asking to see Marietta; but his wife intervenes. In town Warrington hears Marietta singing "Ship Ahoy" with marionettes. Warrington shows Marietta the town; but a reward for her is announced. He helps her escape. In a boat he sings "I'm Falling In Love" to her. An officer takes the princess Marietta to the Governor. Marietta is dressed up; Julie comes in and says that the Governor ordered Warrington to leave town, but he's coming. The uncle arrives and reprimands Marietta, who says she loathes Don Carlos. The uncle says she must sail that night, and he threatens to have Warrington shot for treason if she sees him. Marietta tells Julie to warn Warrington.
At the ball Don Carlos is drunk. Warrington goes in and talks with Marietta, who says she is sailing Friday. As he is leaving, she sings "Ah, Sweet Mystery of Life," and he sings it back. They part, and Marietta tells her uncle she will marry Don Carlos. Warrington sneaks in. He and Marietta are arrested by his men and escape to the wilderness.
This musical entertains with fine music while expressing the democratic theme of a princess leaving the aristocracy to marry a soldier in the wilderness.