The story: At the period when the Pharaohs ruled over Egypt, Aida, daughter of Amonasro, King of Ethiopian, having fallen a prisoner into the hands of the Egyptians, and being brought to Memphis, was given as a slave by their King to his daughter Amneris, who, captivated by the grace and beauty of the unknown maid, took her into favour as a friend and sister. Radames, a young captain of the King's guards, secretly beloved by Amneris, on beholding Aida falls in love with her, and his passion is reciprocated by Aida. The proud daughter of the Pharaoh, suspecting a rival in her slave, swears vengeance should her doubt prove a certainty. Meanwhile war is again declared between Egypt and Ethiopia, and Radames, appointed leader of the army, departs from Memphis to fight the Ethiopians, who, headed by their King, have invaded Egypt and invested Thebes. The enemy defeated, Radames enters the delivered city victorious, laden with spoil, and followed by the prisoners, among whom is Amonasro himself, disguised as an officer. Through the intercession of Radames the prisoners are set free, with the exception of Amonasro, who being recognised as Aida's father is retained with her, when as a reward for his great services the King grants to Radames the hand of his daughter Amneris. Amonasro in his captivity having noticed the mutual affection existing between Radames and Aida, resolves to take advantage of it for the destruction of his enemies, as there is between the two nations a new war impending. Finding that a secret meeting was appointed between the lovers at night, near the temple of Isis, he conceals himself within hearing and obtains information of the plan of the war, incautiously revealed by Radames to Aida. At this moment Ramphis, the high priest of Isis, emerging from the temple with Amneris, suddenly surprises Radames, who, accused of having betrayed to the enemy his country's cause, gives himself up as a prisoner to Ramphia. Radames, brought to judgment and condemned by the sacred council to be buried alive, is visited by Amneris, who offers him pardon from the King on condition that he renounces Aida for ever. On his refusal, and as the stone is already enclosing him, he discovers Aida by his side, who has contrived to penetrate into the tomb, and is come to prove the depth of her constancy and love by luring his fate.