In this musical version of Ferenc Molnar's play and the 1931 movie The Guardsman, flirtatious and jealous married singers in an operetta test their fidelity when he impersonates a Russian singer to seduce her.
On stage in the musical comedy The Chocolate Soldier Maria Lanyi (Rise Stevens) sings "Come, Come, I Love You Only" with Karl Lang (Nelson Eddy). Backstage they quarrel. Poggie (Florence Bates) defends Maria and says she gave up an operatic career to marry Karl. He tells critic Bernard Fischer (Nigel Bruce) he is jealous of Maria being in love with romance. Maria has had nine lovers, and Karl fears the next. At home Maria sings opera for friends. Bernard tells Karl to shave and love Maria; but Karl objects to Maria singing Tannhauser. On stage Karl and Maria sing a love song.
At a café Karl leaves Maria to bail out a friend. Karl disguised as the Russian soldier Vassili sings in the café and joins Maria and Bernard, praising her. Karl changes and returns. He and Maria clash while practicing, and Maria gets flowers. Karl demands to see the card. He informs Bernard he is the Russian and tells Maria he must go overnight to Olmutz. Maria expects Vassili and lies about the card. Maria draws a beard on half of Karl's photo and tells Poggie that her lovers were only admirers. Vassili calls on Maria, and they discuss her husband. Vassili sings for her. When Maria sends him away, he is secretly happy; but she calls him back and says her husband has gone away overnight. Karl comes back and tells Maria he missed his train. Suspicious, he asks her and the servants questions. Karl leaves for the train and comes back as Vassili, singing Maria a serenade. Maria sings love songs to Vassili too. Maria says that Karl has female admirers and gets angry at Vassili for saying he has too. Maria says she does not want to see Vassili again and kisses him. Bernard tells him to follow her. Maria says good-bye but tosses the keys off the balcony to Vassili.
Karl returns home the next day and tells Maria his performance was sensational. On stage Karl sings "Chocolate Soldier" with Maria. She finds his door locked, and he appears on stage as Vassili, singing "Come, Come, I Love You Only" with her. Offstage Maria laughs at Karl and says she was not taken in at all but decided to play along; his kiss gave him away. Back on stage, Karl sings "Forgive" to Maria, and they reprise "Come, Come" one more time.
This operetta adds music to the comic irony of the pretense
as the audience is kept guessing whether she knows it is Karl