Part I

Part 1 (original Act II, scenes 3-11)

Cornelia, the abject widow of Caesar’s defeated rival Pompey, is now a slave in the harem of Tolomeo. Tolomeo was formerly the ally of Pompey, but he ordered his murder in order to ingratiate himself with the stronger of the Romans, Caesar. Separated from her young son Sesto, Cornelia is sought as a wife by Achilla, a general in the service of Tolomeo – and as concubine by Tolomeo.

Tolomeo tricks Achilla, offering him Cornelia as a prize if he achieves the assassination of Caesar. In the meantime he tries to make her submit to him. Cornelia finds no honourable way out, and decides to abandon her son and commit suicide. Her son is secretly conveyed to her by Nireno, the agent of Cleopatra. Appalled by her condition, Sesto promises to become the instrument of bloody revenge.

Just as Cleopatra – in the guise of Lidia – is about to complete her seduction of Caesar, the alarm is raised by his attendant Curio. Hearing the people outside calling for Caesar’s death, she reveals herself to him, and begs him to save his life. In so doing, she finds that she is in love with him – which was not part of the plan. Nor is it part of the plan for him to dash into battle recklessly, endangering his own life and those of his men and hers. She finds all her confident plans have come to nothing, and that she is a different person than she reckoned.

In the harem, Cornelia understands that she is Tolomeo’s chosen companion for the night. Sesto plans to take him by surprise, but Achilla barges in, urging Tolomeo to join the fight against the Romans. Achilla explains that Cleopatra’s forces have gone over to the Romans. He asks for assurance of his price for loyalty – Cornelia – but is haughtily dismissed by Tolomeo. When they leave, Sesto’s failure edges him toward suicidal despair. Cornelia prevents him; there is a chance that with Nireno’s help they may yet avenge Pompey’s betrayal and murder.

Part II

Part 2 (original Act III)

Achilla resolves to join Cleopatra’s forces, reacting against Tolomeo’s treachery.

Cleopatra is her brother’s prisoner. With Caesar assumed dead, and Cornelia and Sesto disabled, she has no hope of help from the Romans.

Caesar survives – separated from his men in a desperate naval battle, he is carried by the current to a remote shore. He sees no way forward until he overhears the dying words of Achilla, offering to Nireno and Sesto the seal which will secure the loyalty of his remaining force. Caesar obtains the seal from Sesto, and goes back into action. Sesto perceives this as justice, at last.

Cleopatra prepares to die, but is rescued by Caesar.

Cornelia plans to murder Tolomeo when he tries to rape her. Instead, Sesto takes her weapon and dispatches the defenceless Tolomeo. Sesto is at last the son his mother wanted.

As Caesar is acclaimed lord of the world and Rome’s emperor, Cleopatra declares herself his tributary queen. They proclaim mutual love, and welcome peace. Egypt is subdued by Rome.