Presented with three intervals.
Sung in Italian with Russian subtitles.

Act I

Nabucco, the king of Babylon, is at the gates of Jerusalem. High Priest Zaccaria, to instill courage into the faithful Jews, leads in a prisoner, Fenena, daughter of Nabucco and leaves her in the custody of Ismaele. Fenena loves Ismaele, whom she rescued one day from Babylonian prison. Ismaele is about to drag Fenena away through a secret door, when Abigaille bursts into the temple, leading a band of Babylonians. Abigaille, who has also been in love with Ismaele since she met him in Babylonia, hates Fenena. She might be disposed to pardon the girl, she confides to Ismaele - who disdainfully refuses - if he will renounce Fenena in her favour. In the meantime all Jews rush for shelter in the temple, terrified by the relentless advance of Nabucco at the head of the Assyrian and Babylonian armies. Abigaille, the king rides up to the temple. Zaccaria confronts him and threatens divine wrath on his impiety, seizes Fenena and raises his dagger. But Ismaele rapidly intervenes and gives Fenena back to her father. Nabucco is once again master of the situation. Zaccaria and the people curse Ismaele.

Act II

 Abigaille has learnt from a document, which Nabucco had kept hid­den, that she is not the king’s elder daughter but a slave. Nabucco, who is away from the capital, has appointed his legitimate daughter Fenena to act as his regent. High Priest of Bel comes to inform Abigaille that Fenena has set all the Jewish prisoners free. The time has come, he suggests, to stage a coup.
A false rumor has already been put about that Nabucco has been killed in battle. Abigaille is exul-tant. She dreams of power and revenge upon Fenena and Nabucco.
Fenena goes to be converted to the Jewish religion. The "miracle" is announced by Ismaele to the other Levites as they gather in the hall. But they refuse to listen to the man whom they believe to be a traitor. Zaccaria enters, accompanied by his sister Anna and by Fenena, and Ismaele deserves forgiveness. Abdallo, loyal to the regent, enters, announcing the king’s death and Abigaille’s intention to seize power. He urges Fenena to escape. The girl decides instead to join the rebels to defend the legitimate throne. But she is arrested by Abigaille, surrounded by the High Priest and a crowd of Babylonians. As Abigaille orders Fenena to relinquish the crown, Nabucco appears. Cursing Bel, who has made traitors of the Babylonians, and mocking the defenceless god of the Jews, he orders everyone to wor-ship him as the sole divine authority. Zaccaria threatens Nabucco with the punishment of heaven. The king orders the priest to be arrested and put to death with his people. Fenena wishes to die with her kin. Nabucco forces her to kneel before him and proclaims "I am no longer king, I am god". A flash of lightning strikes Nabucco on the head. Abigaille scornfully picks up Nabucco’s crown.

Act III

The High Priest of Bel presents Abigaille the death sentence for the Jewish prisoners and Fenena. Nabucco enters, looking ill and dishevelled. Abigaille orders him to affix his royal seal to the parchment. He does, but at once regrets his action, imagining Fenena’s fate. Abigaille is irremovable, saying to Nabucco, that if Fenena dies, he still has another daughter. Nabucco replies angrily that she is only a slave girl. But Abigaille, drawing from her bosom the doc-ument certifying to her servile birth, tears it up before the king’s eyes. He calls his guards but, as Abigaille triumphantly tells him, they are no longer at his command: they have orders only to escort him as a pris-oner to his rooms. The Jews in captivity lament their unhappy fate. Zaccaria reproaches them for their resignation and predicts the Babylonian empire will be destroyed.

Act IV

Nabucco is a prisoner. He sees Fenena being led to execution. In despair at his powerlessness to act, he implores forgiveness from the god of the Jews. Abdallo and his faithful guards enter. Proudly drawing himself up, Nabucco orders Abdallo, who joyfully obeys, to follow him: as king of Assyria he will rout the traitors, save Fenena and free the Jewish people from captivity.
Fenena and the Jews condemned to the block arrive. As Zaccaria blesses the girl who is about to win the palm of martyr-dom, Nabucco bursts in, his sword drawn. The idol of Bel crashes to the ground. All those present fall to their knees in wonder and praise the god of Israel. Abigaille, who is remorseful of her offences, asks Fenena to forgive the evil she has done her. Before dying, she begs Nabucco to marry the girl to Ismaele. Zaccaria predicts for Nabucco as the reward for his faith in Jehovah who will protect him, dominion over all the kingdoms of the world.

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