Matilda tells Ottone that Adelberto has abducted Teofane. Gismonda is triumphant at her son's actions, but Matilda tells her she will change her tune when she sees her son's head cut from his shoulders. Gismonda retorts by revealing to Ottone that it was due to Matilda that Adelberto managed to escape. Matilda admits this is true, but she is sorry she helped Adelberto and would now like to kill him herself (Aria: "Nel suo sangue"). Emireno comes in with Adelberto in chains. Ottone orders Adelberto to be executed, but Matilda demands the right to run him through herself. However she cannot bring herself to do it, realising that she still loves him. Gismonda grabs the knife from Matilda and is about to commit suicide, when Teofane rushes in and she and Ottone are joyfully reunited (Duet: "A’ teneri affetti"). Teofane explains that she now knows that Emireno is really her brother; Gismonda and Adelberto ask for and receive Ottone's forgiveness and pledge him their loyalty, and Matilda accepts Adelberto's offer of marriage. All celebrate the fortunate turn of events (Chorus: "Faccia ritorno l’antica pace").