Visiting Italy with his brother Rutillio, Arnoldo has fallen in love with Zenocia, but is vexed by Count Clodio's ancient right - the jus cunni - to sleep with the bride on the wedding night. The couple defy the custom of the country, and after marrying, they and Rutillio flee the country by sea, pursued by Clodio and Zenocia's father Charino. The fugitives are captured by the Portuguese sea-captain Leopold, but the brothers escape to Lisbon. Meanwhile, Manuel de Sosa, Governor of Lisbon, and his sister Guiomar vainly chide Duarte - Guiomar's son-for his arrogant ingratitude. Zenocia's captor Leopold presents her as a servant to the beautiful Hippolyta, whom he loves; but Hippolyta has herself fallen in love with Arnoldo, and through the offices of her servant Zabulon, she vainly attempts to seduce him. Meanwhile, Rutillio is provoked into fighting and (as he thinks) killing Duarte, and he seeks sanctuary of Guiomar, whose promise to help him she keeps even when she realizes who it is Rutillio has apparently killed. She warns him never to approach her again. Doubly fugitive, Rutillio is now arrested as a spy, but his bail is met by Sulpitia on condition he work as a prostitute in the brothel she runs, which caters to a female clientele. He agrees. Meanwhile, Leopold has arranged a meeting between Arnoldo and Zenocia, in the hope that, overhearing the lovers' reunion, Hippolyta will turn her affections from Arnoldo to him. Hippolyta, however, jealously attempts to force her will on Arnoldo and to kill Zenocia, but is prevented from doing so by the Governor. Thus thwarted, Hippolyta employs Sulpitia's black magic to put a fatal curse on Zenocia. Meanwhile, the exhausted Rutillio is rescued by the disguised Duarte (now recovered from his wounds a reformed man), who persuades him to pay court to his mother Guiomar in order to test the constancy of her grief. At last, conscience-stricken at the pathos of Arnoldo's grief for Zenocia's fatal illness, Hippolyta has Sulpitia lift the spell; likewise moved, Clodio repents of his pursuit ofZenocia, and repeals the custom of his country; Guiomar pretends to accept Rutillio's hand, but then (despite her growing love for him) has him arrested for the murder to which Rutillio confesses. Now Duarte reveals his identity, and is reconciled to his mother, who accepts Rutillio's hand in earnest; Hippolyta accepts the hand of the constant Leopold; and Arnoldo and Zenocia are restored to health.