The three-act opera Julius Caesar in Egypt is a historical episode inspired by Caesar’s military campaign in Egypt in 48-47 BC. 

Act One – Caesar arrives in Egypt in pursuit of his enemy Pompey, who fled with his army after suffering defeat at Pharsalus. Cornelia, Pompey’s wife, and his son Sesto plead for mercy and peace, which the victor generously grants, though none of them are aware that King Ptolemy of Egypt had already killed Pompey in order to win Caesar’s approval. When the Egyptian general Achilla offers him the head of the enemy, Caesar condemns the gesture with disgust and orders that the remains of his enemy be given heroic honors. Achilla informs Ptolemy of Caesar’s unexpected decision and promises to kill him in exchange for Cornelia’s hand. Cleopatra, Ptolemy’s sister, tries to seduce the Roman leader under the guise of the escort girl Lidia, using Caesar’s favor to seize the Egyptian throne, to which she is entitled as firstborn. The act ends when Sesto unsuccessfully challenges Ptolemy and is arrested along with his mother.  

Act Two – Cleopatra, still pretending to be only Lidia, seduces Caesar in the famous scene of “theatre within theatre.” At the same time, Cornelia and Sesto spend their worst days in captivity, humiliated and unsuccessfully trying to exact their revenge. When Caesar learns that a conspiracy is being planned against him, Cleopatra reveals her identity and begs him to flee. To avoid Ptolemy’s assassins, Caesar throws himself into the sea. Achilla brings the king news of the death of the Roman leader, but does not receive Cornelia as a reward, as Ptolemy has fallen in love with her himself in the meantime. 

Act Three – Ptolemy is initially victorious in the conflict between the Romans and the Egyptians. Cornelia and Sesto fall into enemy hands after a young man tries to kill the king; Cleopatra is captured, while rumors of Caesar’s death spread. However, Caesar survived, managing to escape and swim to the shore where he met with Sesto to gather an army against Ptolemy. He soon frees Cleopatra and defeats Ptolemy’s army. Sesto then kills Ptolemy and avenges his father. With great joy from the people and soldiers, Cleopatra is crowned queen, while the two lovers pledge each other loyalty and love.