'Aida' (1871) was the result of a commission from Ismail Pacha, who wished to enhance the reputation of his new opera-house at Cairo by the production of a work upon an Egyptian subject from the pen of the most popular composer of the day. The idea of the libretto seems to have been originally due to Mariette Bey, the famous Egyptologist, who had happened to light upon the story in the course of his researches. It was first written in French prose by M. Camilla du Locle in collaboration with Verdi himself, and afterwards translated by Signor Ghislanzoni. Aida, the daughter of Amonasro, the King of Ethiopia, has been taken prisoner by the Egyptians, and given as a slave to the princess Amneris. They both love the warrior Radames, the chosen chief of the Egyptian army, but he cares nothing for Amneris, and she vows a deadly vengeance against the slave who has supplanted her. Radames returns in triumph from the wars, bringing with him a chain of prisoners, among whom is Amonasro. The latter soon finds out Aida's influence over Radames, and half terrifies, half persuades her into promising to extract from her lover the secret of the route which the Egyptian army will take on the morrow on their way to a new campaign against the Ethiopians. Aida beguiles Radames with seductive visions of happiness in her own country, and induces him to tell her the secret. Amonasro, who is on the watch, overhears it and escapes in triumph, while Radames, in despair at his own treachery, gives himself up to justice. Amneris offers him pardon if he will accept her love, but he refuses life without Aida, and is condemned to be immured in a vault beneath the temple of Phtha. There he finds Aida, who has discovered a means of getting in, and has made up her mind to die with her lover. They expire in each other's arms, while the solemn chant of the priestesses in the temple above mingles with the sighs of the heart-broken Amneris.