The King counsels the Cardinal to celebrate the Duchess's marriage to Alvarez and let his anger go, while the Cardinal protests that he just doesn’t understand why his nephew would give her up. The secretary wrangles some bumbling servants to present some kind of play for the King and court, in celebration of the Duchess's marriage. Columbo joins in part of the masque, vizarded, and the masquers get Alvarez to join in a little. They take him offstage, ostensibly to costume him, and then bring him back dead. Columbo takes responsibility immediately. All the other masquers have escaped. Columbo protests that this murder was justice and revenge, and accuses the Duchess of witchcraft and malice. He produces the letter the Duchess wrote asking him to release her, which he says is proof of her attempt to discredit his fame. The King says he is just as much to blame for Alvarez's murder, since he sided with the Duchess, and refuses to pardon Columbo. The Cardinal counsels Columbo to beg for his life, but Columbo refuses and is escorted to prison. Some time has passed, apparently, and Hernando in conversation with two lords remarks on the King's pardoning Columbo and wonders whether they will manage to marry him to the Duchess yet. The lords talk about murdering Columbo. Columbo and Alfonso pass over the stage with their train. They all comment on his triumphant delivery from the jail and Hernando goes off to comfort the Duchess. The King and Cardinal enter and the King orders the Cardinal to go to the Duchess and try to reconcile her “to some peace." The Secretary fetches Celinda to come entertain the Duchess and insinuates that he’d like to sleep with her. The Duchess asks Celinda what she thinks of Columbo and laments all the misery he wrought for her. Placentia enters to announce Columbo's presence. Columbo forces his way into her chambers and tells her she is “not worth / The humblest of my kinder thoughts”. He curses her with his revenge and says he’ll kill anyone else she ever presumes to marry, either at the altar or while they are in bed together. He then apologizes to Celinda and says she's worth far more than the Duchess, and exits. The Duchess reprimands Celinda for inviting Columbo's attentions, and Celinda sticks up for herself, attacking the Duchess's jealousy, and leaves. Hernando arrives to entreat the Duchess to devise some revenge for Alvarez's murder.