Act I Tyrol. at the start of the 18th century.
Luisa, the daughter of Miller, an old soldier, is being hailed on her birthday in front of the family house. The girl searches the festive crowd for Carlo, her sweetheart. The young man finally arrives, and the lovers happily greet one other. Miller, however, has reservations about Carlo. The bell calls the people to Mass: everyone departs for the church – with the exception of Miller, who has been detained by the appearance of Wurm, Count Walter's secretary. The man informs Miller that he is in love with Luisa, and that he alone is worthy of the girl's hand. Miller, however, tells the secretary that he will give Luisa away only to a man whom she loves as well. In his rage, Wurm reveals that Carlo is in fact none other than Count Walter's son, Rodolfo.Wurm notifies the other father, Walter, of Rodolfo's love. The Count, however, has already arranged a marriage for his son: he has had him engaged to the wealthy widow Duchess Federica. Nevertheless, the young man has resolved to frankly admit to the duchess that he is love with another. Miller reveals “Carlo's” true identity to his daughter, as well as the fact that the young man is already betrothed to another. Rodolfo arrives, swearing that Luisa and none other will be his wife. Walter then enters the Miller home, intending to have both Luisa and Miller locked up right away. But something halts him in his tracks: Rodolfo threatens that if he takes away the girl, he will tell all the world the story of how he became count. Walter releases her.
Act II
Wurm informs Luisa that her father has been thrown in prison for threatening the count. There is only way for him to be freed: if she writes in a letter that she never loved Rodolfo himself, only his wealth, and it is really only Wurm she loves. Luisa must also fulfil two other conditions: if anyone asks, she must avow that she wrote the letter of her own free will, and she must attest to this in the castle before Duchess Federica.Wurm reports to Walter that Luisa's letter is already on its way to Rodolfo. They recall the terrible memory of how together they killed Walter's cousin to gain the title of count. If this gets out, it will mean doom for both of them. Federica arrives, and Wurm introduces Luisa to her. The girl “admits” to the duchess that she only loved Rodolfo for his wealth and it is actually Wurm she is in love with. Rodolfo receives Luisa's letter. The wronged lover is about to challenge Wurm to a duel when the latter shoots his pistol in the air, bringing the inhabitants of the castle running. Wurm uses the opportunity to flee. Walter exhorts his son to avenge himself by marrying Federica.
Act III.
While the church is being prepared for Rodolfo and Federica's wedding, Miller reads the letter his daughter has written to Rodolfo: Luisa wishes to summon the young man to a final meeting before taking her own life. Miller implores his daughter to go on living for her father's sake: they will leave the village that night.While Luisa is praying, Rodolfo comes into the house. Before the girl can finish her prayers, he sprinkles poison into one of the drinking cups. He shows Luisa the letter in which she declared her love for Wurm and asks her whether the writing was in fact her own. Luisa answers affirmatively, at which point the young man drinks from the poisoned cup. Luisa later takes a sip from the same cup. Rodolfo bitterly confesses that they have both drunk the poison he gave them and are close to death; he asks the girl to answer once again, sincerely: does she truly love Wurm? Luisa admits the truth and asks for her father's blessing before dying. Rodolfo stabs Wurm as he enters, and then himself collapses dead.