Act I – Love
Miller has organised a birthday party for his daughter, at which Carlo, a mysterious young man with whom Luisa is in love, also appears.
Wurm, who works for Count Walter, has also set his sights on Luisa. Miller does not trust Carlo and his doubts are confirmed by Wurm, who tells him that Carlo is in fact Rodolfo, the count’s son. Miller envisages his daughter handed over to a seducer.
Wurm informs Walter of Rodolfo’s love for Luisa. Walter takes Rodolfo to task and orders him to marry the recently widowed Federica, who is not only a good catch but has loved Rodolfo since her youth.
Rodolfo finds a way of telling Federica that he loves Luisa, but Federica will not renounce her love for him.
Luisa waits for Carlo but instead is confronted by her father, who reveals her lover’s true identity and his forthcoming marriage. Rodolfo intervenes, declares his love for Luisa and proposes to her. At this moment, Walter arrives and accuses Luisa of being nothing more than a common whore. When Miller protests violently against this, Walter has both father and daughter arrested. But when Rodolfo threatens to disclose the secret of how his father came into his title, Walter backs down and sets Luisa free.
Act II – Intrigue
Luisa learns that her father has been charged. Wurm offers her a solution: she should confess in a letter that she loves him and has only been playing games with Rodolfo. She should then also confirm this before Duchess Federica, after which her father will be freed.
Wurm informs Walter of the successful intrigue. Together, they recall their treacherous murder of Walter’s predecessor in office, which Rodolfo had witnessed by chance.
Federica is assured that Rodolfo will marry her. Under pressure, Luisa confirms the contents of her letter. Walther and Wurm are triumphant. Shocked when he reads Luisa’s letter, Rodolfo challenges Wurm to a duel. The latter, out of fear, fires into the air and thereby fetches help. Walter advises his desperate son to take his revenge by marrying Federica.
Act III – Poison
Laura and the village women try to comfort Luisa. Miller has been freed from prison. He finds on Luisa a farewell letter to Rodolfo; by appealing to her filial love, he succeeds in stopping her suicide.
Rodolfo enters and unnoticed pours poison into a glass. Anxious for her father, Luisa confirms to him the authenticity of the letter that Wurm forced her to write. Rodolfo urges Luisa to share a drink with him. Then he reveals to her that the drink was poisoned and that they are soon going to die. Faced with death, Luisa considers herself to be released from her vow and tells Rodolfo that she has only ever loved him. They both dream of being reunited in heaven.
Walter and Wurm enter. Rodolfo curses Wurm, then collapses and dies beside the lifeless Luisa.