Count Lodovico has been banished from Rome for debauchery and murder. His friends promise to work for the repeal of his sentence and return to Rome.
Duke Brachiano has fallen hard for the beautiful Vittoria. Both are married: he to Isabella and she to Camillo. Flamineo, brother to Vittoria and aide to Brachiano – with the help of Vittoria’s maid, Zanche – paves the way for the pair to consummate their affair. Cornelia, the siblings’ mother, disgusted by the behavior of her children, foils their plans for the evening.
Isabella, Brachiano’s wife, pleads with her husband to rein in his straying affections, but he refuses. In an effort to preserve her son Giovanni’s fortune, she pretends to her brother Duke Francisco and her husband’s uncle Cardinal Monticelso, that separation from Brachiano is her idea. They do not buy it. They send Camillo away to bait Brachiano into making a move with Vittoria that will prove their suspicions.
With Flamineo’s help, Brachiano does make a move: he has Camillo and Isabella murdered.
Vittoria stands trial for Camillo’s murder. Monticelso finds her guilty of murder by way of lust and lechery. She is sent to a women’s prison. News arrives of Isabella’s death, cementing in Francisco a thirst for revenge.
Pursuing this revenge, Francisco hires the formerly banished Lodovico (who was in unrequited love with Isabella) and his associate Gasparo as assassins. Brachiano visits Vittoria and plans her escape.
Monticelso, newly elected Pope, excommunicates the couple, but that doesn’t stop them from getting married. Three unknown guests are welcomed to the reception by Brachiano: General Mulinassar and two monks—they are Francisco, Lodovico, and Gasparo in disguise!
Marcello, younger brother to Vittoria and Flamineo, challenges the latter to a duel. Instead, Flamineo murders him in cold blood. Brachiano refuses to pardon Flamineo for the deed. The festivities continue with a tournament. His helmet poisoned by Francisco and his cohorts, Brachiano falls. He is ultimately murdered by Lodovico and Gasparo.
Zanche, who has fallen in love with General Mulinassar (Francisco in disguise), divulges to him the truth about the murders of Camillo and Isabella. She plots to rob Vittoria as comeuppance. The same night, Lodovico and Gasparo plot to murder Vittoria, Flamineo, and Zanche. Flamineo and Vittoria have their own plots. Giovanni does, too. All the devilish plots converge in a final bloody rampage.