Alexandria, 48 BC. – Cleopatra and her younger brother Tolomeo are fighting for sovereignty over Egypt. Caesar, who beat his adversary Pompey and followed him to Egypt, enters Alexandria, where the defeated man’s seeking refuge. Pompey’s wife Cornelia and son Sesto acknowledge Cesare’s victory, but beg him to make peace with his rival. The Roman commander‘s willing, but Tolomeo’s had Pompey killed, to make a good impression on Caesar. The Emperor‘s horrified by the crime, Cornelia falls into deep despair and Sesto swears revenge. Cleopatra sees a chance of winning Caesar’s favour and ascending the Egyptian throne with his help. Disguised as a servant called Lydia, she approaches Caesar, who falls under her spell at once. Tolomeo’s adviser and military commander Achilla’s fascinated by Cornelia. The widowed Roman woman rejects his advances with contempt. Achilla offers Tolomeo a deal: He declares himself ready to murder Cesare, if he can marry Cornelia. When Sesto challenges Tolomeo to a duel, he and his mother are arrested. Act 2 Lydia, alias Cleopatra and Caesar meet at »Parnassus«, a place of longing. They fall in love. Achilla tries again, using force, to win Cornelia for himself. In vain. He turns to Tolomeo, who dismisses him scornfully. The Egyptian King desires Cornelia too and has her taken to his harem. Caesar finds out from his companion Curio that Tolomeo wants to kill him. Cleopatra reveals her true identity and promises to help the Romans. Caesar flees. Achilla calls on Tolomeo to fight Cleopatra’s and the Roman troops. Caesar apparently drowned at sea trying to escape. When Tolomeo refuses to give Achilla Cornelia’s hand as promised, the military commander feels betrayed and changes sides. Act 3 Tolomeo returns victorious from battle and humiliates his sister. Mortally wounded, Achilla gives Sesto his ring, which guarantees allegiance from Tolomeo’s troops. Caesar, who managed to swim ashore, takes command with this ring, freeing Cleopatra and bringing her to safety. Tolomeo’s been trying to take what Cornelia won’t give him by force. Sesto bursts in, overpowers the Egyptian King and kills him. Caesar crowns Cleopatra Queen of Egypt. They profess their love and fidelity.