Act I
In the Palazzo Ducale in Venice, the Council of Ten and the members of the government are meeting, among them Loredano and his friend Barbarigo. The two learn that the apparently serene Doge has preceded them into the chambers. Conducted out of prison, Jacopo Foscari, son of the Doge, waits to be summoned before the Council. He salutes his beloved Venice that he has not seen for so long because he has been exiled from the city. An official tells him to hope for an act of clemency, but Jacopo rants against the atrocious hate he has experienced. His wife Lucrezia Contarini pleads his case before the Doge, who after all is his father. The Doge replies that she may hope for heavenly justice. When she hears that Jacopo has once more been condemned to exile, Lucrezia gives vent to her fury.
The senators comment the sentence: Jacopo has not confessed, but his guilt is proven by the letter he sent to the duke Sforza in Milan. It is therefore right that he must return to Cretian exile. The impartiality of Venetian justice should be clear to everyone when even the Doge's son is condemned.
The Doge muses about his destiny as a prince, with his power much reduced by the Council of Ten, and as a father, unable to help his son in his misery. Lucrezia enters and pleads with her father-in-law to annul Jacopo's sentence, but the Doge tells her that Venetian law will not allow it. Seeing the Doge in tears over his son’s fate, Lucrezia begins to hope.
Act II
Wasting away in his cell, Jacopo perceives a ghost in a moment of delusion. Carmagnola, the famous commander executed in Venice, advance toward him holding his severed head. Terrified, he faints. He wakes up in Lucrezia’s arms. She has come to give him the sentence: not death, but exile, forcing them to part forever.
The Doge arrives and the three embrace, deeply moved. Jacopo now sees paternal love in his father instead of the former authoritarian severity. Accompanied by guards, Loredano arrives to inform Jacopo that the Council has decided that he must leave at once for Crete. The three embrace once again, but Loredano separates them mercilessly. Jacopo is taken away by the guards. The counsellors and governors unite to confirm the sentence. The Doge enters to preside. Jacopo is admitted, asking justice of his father and claiming his innocence, but the Doge can only advise his son to resign himself. Lucrezia arrives with Pisana and other ladies, holding their two children by the hand. Jacopo runs to embrace them and makes them kneel before the Doge, pleading for mercy. Barbarigo is touched by this scene and tries to soften the resolve of implacable Loredano in vain. Jacopo must return to Crete alone, without his family. Faced with this future, Jacopo senses that death is drawing closer.
Act III
St. Mark's square fills with people. Loredano and Barbarigo arrive and observe the happy crowd, oblivious of the Foscaris’ destiny. Suddenly, a galley is coming into port to take Jacopo to Crete. Before embarking, he bids farewell to Lucrezia and his children. But Loredano once more separates them to hurry up the departure. As Jacopo boards the galley, Lucrezia faints.
In his private rooms, the Doge bemoans his tragic destiny: three of his sons have died young and a fourth is now being banished. Barbarigo enters unexpectedly with a letter. A certain Erizzo has written to confess the crime of which Jacopo has been condemned. The Doge thanks the heavens, but his joy does not last. Lucrezia arrives in tears to announce Jacopo’s death at the moment the boat set sail.
Then the Councilmembers headed by Loredano are brought before the Doge. They have come to ask him to resign given his advanced age and his state of shock because of his son's death. Twice the Doge’s request to abdicate had been denied. He thus took an oath to remain in his functions until death, now he wants to honour his pledge. But the Council does not flinch. The Doge hands over the ring and the crown of office. Lucrezia arrives to accompany him out of the palace when Loredano tells him that Malipiero is the new Doge. At this news, the old man dies.