Author and actor Erich Remberg learns from his producer that his musical has been panned by the Viennese critics, who seem to prefer more romantic and less sexy productions these days. In order to find the inspiration to write an operetta, Erich goes with his friend Peppi to the von Keller castle in Tyrol. They are greeted by the eccentric Baron von Keller, who proudly shows them nonexistent antiques that only he can see. While investigating some strange noises he's heard in the middle of the night, Erich meets von Keller's daughter Loni, who is also curious about the room. She shows him a painting representing the Napoleonic invasion of Austria and tells him of her great-grandaunt, who scandalized the family. Erich imagines the scene with Loni playing the role of the baroness of the von Keller castle and himself as her French lover: Back in 1809, a French colonel insists on quartering at the von Keller home, and Loni dines with the invaders with reluctance. Lieutenant Pierre Laval approaches her later with romantic propositions, and she tells him that she will always be faithful to Augusto, an Austrian nobleman, who is away fighting the Napoleonic armies. However, she allows Pierre to woo her at a dance in the village, and when the French soldiers are ordered to retreat, Pierre chooses to stay behind with Loni. As the Austrians approach, Loni fears for Pierre's safety, and when Augusto and her father, the baron, arrive home, Pierre hides. Augusto proposes, but Loni is indifferent. Pierre disguises himself as the new butler and then convinces Loni to escape with him to the French encampment. The fleeing couple are caught trying to cross the Austrian lines, and Pierre reveals his true identity as one of Napoleon's men. Augusto orders Pierre's arrest, but two shots ring out, signaling a truce. The scene now shifts to a Viennese theatre, where Erich and Loni act out their roles in Erich's smash romantic musical. While taking their curtain calls, Erich and Loni joyfully announce their upcoming wedding to the audience.