Ernst Lubitsch directed this comedy based on an operetta by Jacobson and Dormann in which a charming officer loves a violinist but has to marry a princess.
In Vienna after a woman visits his apartment, Lt. Niki von Preyn (Maurice Chevalier) wakes and sings about being in the army. Max (Charlie Ruggles) asks Niki to go with him to see a beautiful woman who plays violin. Niki says she looks like Max's wife. Franzi (Claudette Colbert) brushes off Max and walks with musical Niki, who plays piano for her. Niki kisses her and suggests having breakfast together. They sing, "Breakfast Time, It Must Be Love." King Adolf XV (George Barbier) of Flausenthurm gets a telegram from the Austrian emperor, who cannot meet them at the station. During the parade Niki smiles at Franzi, but Adolf's daughter Anna (Miriam Hopkins) thinks he is laughing at her and is offended. Adolf wants to punish him. Anna cries, but Niki charms Adolf and her and is made their adjutant. Anna winks at him. Niki finds Franzi and dances and sings with her. To her ladies in waiting Anna sings "I Like Him." When Adolf says no, Anna threatens to marry an American. Adolf calls the Emperor and agrees to the marriage. Niki learns he is engaged to Anna, but he tells Adolf he will not leave Vienna. The Emperor congratulates Niki, who submits. Franzi packs a bag and leaves a note with her garter for Niki.
In Flausenthurm they prepare for the wedding. Married Niki says goodnight to Anna, who is left alone and cries. Niki leaves Anna and Adolf at dinner and goes out. He sees Franzi playing violin, and a policeman takes her to his room. Niki returns to the palace singing and mollifies Anna and Adolf. Anna tells the king that Niki is stepping out with a violinist. Anna plays classical piano, but Niki walks out. Franzi is taken to Anna. They slap each other, cry, and talk about Niki. Franzi plays jazzy piano and sings with Anna, suggesting better lingerie. Franzi tells Anna to take good care of Niki, who gets a farewell letter from Franzi. He hears Nikki playing upbeat music and sees her in a new slip. He gets a drink, and she kisses him. In the final scene he sings of his new joy and retirement from the army.
Though set in the mid-19th century, this comedy reflects the changing sexual mores of France in the acceptance of all-night dates that conclude with breakfast.