Act 1: Jerusalem
'Therefore these are the words of the Lord: I am about to give this city into the hands of the Chaldaeans and of King Nebuchadrezzar of Babylon, and he will take it. The Chaldaeans assailing this city will enter and set it on fire…’
(Jeremiah 32:28—29)
The city is besieged by the Babylonian king Nabucco. In the Temple of Solomon, the Israelites pray for salvation. The High Priest Zaccaria tells the people that there is hope: Fenena, the youngest daughter of Nabucco, has been taken prisoner. The Jewish commander Ismaele is in love with her. A Babylonian detachment breaks into the temple led by Abigaille, the eldest daughter of Nabucco. Abigaille will keep the Israelites alive if Ismaele abandons Fenena for her. Ismaele rejects her love. Nabucco breaks into the temple with his army. To stop the enemy, Zaccaria threatens to kill Fenena, but Ismaele frees her. Zaccaria curses the traitor, Nabucco orders the destruction of the temple, Abigaille vows to destroy the enemies.
Act 2: The Impious One
‘See what a scorching wind has gone out from the Lord, a sweeping whirlwind which whirls round the heads of the wicked’
(Jeremiah 30:23)
Royal apartments in Babylon. Nabucco has gone on a new campaign against the Israelites, leaving the throne to his youngest daughter. Abigaille discovers a secret document that proves she is the daughter of slaves and therefore will not be able to rule Babylon. The High Priest of Bel reports that Fenena has released the Israelite captives. He encourages Abigaille to spread the rumor that Nabucco has died and take the throne.
In the dungeon, Zaccaria prays for the salvation of the Israelites. The priests curse Ismaele for his betrayal. Zaccaria’s sister Anna intercedes on his behalf: Fenena, who he saved, has converted to Judaism. Abdallo, the head of the Babylonian guard, warns of the conspiracy carried out by Abigaille. Fenena refuses to give up her the crown. Nabucco reappears unharmed saying he has defeated the Jewish god Yahweh, and the Babylonian god Bel has turned his subjects into traitors, so from now on he is the only god. A thunderbolt strikes Nabucco down, he loses his senses. Abigaille takes the crown from her father and pronounces herself Queen of Babylon.
Act 3: The Prophecy
‘Therefore marmots and jackals will skulk in it, desert-owls will haunt it; never more will it be inhabited and age after age no one will dwell in it’
(Jeremiah 50:39)
Abigaille forces the insane Nabucco to sign the death warrant for the Jsraelites and, therefore, for Fenena. In anger, he calls Abigaille a slave, but she tears up the document about her origin. Nabucco pleads to spare Fenena but in vain. He is taken into custody. The Israelite captives await execution. Zaccaria prophesies fall of Babylon.
Act 4: The Broken Idol
‘Bel put to shame, Marduk dismayed; the idols of Babylon are put to shame’
(Jeremiah 50:2)
Through the bars of the dungeon Nabucco sees Fenena being led to execution. In desperation, he prays to Yahweh and his reason is restored. Abdallo and loyal soldiers release him. At the last moment Nabucco stops the execution and grants freedom to the Israelites. Abigaille appears: she has poisoned herself and now is dying, begging forgiveness of everyone.
