A terrace of the Grimani palace in Venice. A festival by night. A merry band of young gentlemen-at-arms in the service of the Venetian Republic, among whom are Maffio Orsini and his friend Gennaro, are celebrating their last evening together in Venice. For tomorrow they must all travel to Ferrara, to the court of Alfonso d’Este and his wife Lucrezia Borgia. This last name spells dread in their hearts, the crimes she has committed being too heinous for her not be execrated. Orsini tells his companions of a mysterious voice which, during a battle at Rimini, warned him and Gennaro of their own deaths at the hand of Borgia. Gennaro pays no heed and falls asleep nearby. They all go off. Meanwhile a gondola approaches and a masked lady steps ashore. She is Lucrezia Borgia, who has come to Venice incognito to see Gennaro, her beloved illegitimate son who has been kept unaware of his origins. While she gazes at him sleeping, she fails to notice that she is being spied upon by her husband and his hired ruffian, Rustighello. They take the young man for a lover of the duchess. Despite the warnings of her sinister confidante, Gubetta, Lucrezia removes her mask and kisses the hand of her son, w h o awakes and begins to court this comely and mysterious lady. He tells her the story of his orphanhood and of his love for the mother he never knew. Lucrezia consoles him, but is interrupted by Gennaro’s friends who now reappear. Too late the duchess puts on her mask and makes a desperate attempt to escape. But Orsini has recognized the infamous Lucrezia Borgia. They all hurl insults at her and unmask her before the amazed Gennaro.
A square at Ferrara. Duke Alfonso meditates revenge and orders Rustighello to have Gennaro slain. Gennaro enters looking pensive. He refuses to follow the merry company on their way to a banquet in the palace of Princess Negroni. I nstead he climbs the flight of steps in front of the ducal palace and with his sword breaks off the first letter of the Borgia coat-of-arms, so that the noble name now reads orgia. Alone on the steps, Gennaro is arrested by the Duke’s hired ruffians. A hall in the ducal palace. Enter Lucrezia who urges her husband to avenge the outrage perpetrated against their name. But the Duke’s only reply is to have Gennaro brought in, who defiantly confesses his crime. His desperate mother does her utmost to defend him and then asks her husband to talk with her in private. She resorts to blandishments, pleas and threats, but nothing will turn the Duke from his intention to have Gennaro slain. His sole concession is to let her choose whether her beloved shall die by poison or by the sword. Gennaro is brought back by Rustighello and the Duke’s other hired thugs. The Duke pretends to forgive Gennaro and invites him to drink from a chalice which Lucrezia herself offers to fill. When all is done, the Duke goes out with his retinue, leaving mother and son alone. L ucrezia tells Gennaro that the wine was poisoned. Handing him a jug containing the antidote, she urges him to flee.
A small courtyard leading into Gennaro’s house. Rustighello and the Duke’s hired ruffians are spying on Gennaro’s house with malicious intent , but the sound of a person approaching momentarily delays his danger. The visitor is Maffio Orsini, who succeeds in convincing Gennaro that he too should attend the banquet at Princess Negroni’s palace. The two men go out together. The hired ruffians prepare to follow them, but Rustighello holds them back: the young man has fallen into a trap still worse than the one they themselves had been laying for him. A hall in the Negroni palace brightly lit and decked out for a festive banquet. At the height of the banquet, the young gentlemen-at-arms, drunk by now, sit down at the table with numerous ladies and the sinister Gubetta, who has crept in among them, pretending to be a Spanish adventurer. To get rid of the ladies, he provokes Orsini and starts ascuffle, which is immediately quelled: there can be no duel because the guests are disarmed , having left their swords at the entrance. A chalice-bearer dressed in black carries a bottle round. They all quaff the wine except Gubetta, who tips his glass over his shoulder and incites Orsini to sing a toast. During his song, in the distance is heard a funeral dirge and a bell ringing the death toll. At first they think it must be a joke played by the ladies, but when the lights slowly go out they all make for the exit of the hall. It is bolted. Suddenly Lucrezia Borgia appears. The party was arranged by her in order to poison all those who outraged her in Venice. But when in consternation she recognizes Gennaro among the guests, she orders the guards to clear the room. Left alone with him, she tries in every way to persuade him to drink the antidote. Gennaro refuses resolutely, preferring to die with his friends, though not without first having avenged them. In fact he picks up a knife from the table and flings himself at Lucrezia. At this point she reveals to him her true identity: Gennaro is a Borgia and is about to murder his own mother. Terrified and by now close to death from the poison, he collapses onto a chair and expires in Lucrezia’s arms.
