THE Argument in the libretto outlines the tangled plot. ‘Aetius [Ezio], an illustrious General of the Imperial Forces under Valentinian the Third, returning from the famous Victory of the Catalonian Fields, where he defeated and put to Flight Attila King of the Huns, was unjustly accused by the jealous Emperor, and by him condemned to die. The Author of this Treachery against the innocent Aetius, was Maximus a Roman Patrician, who being displeased before at Valentinian for attempting the Chastity of his Wife endeavoured, though ineffectually, to engage the Assistance of Aetius to murther the Emperor, artfully concealing his own Desire of Revenge; but knowing that the Loyalty of Aetius was the greatest Obstruction to his Design, he fix’d upon him the Imputation of Treason, and sollicited his Death, intending (as he afterwards did) to make the Populace mutiny against Valentinian, by accusing him of the Ingratitude and Injustice, to which he himself had induced him. All this is historical, and the rest within the Bounds of Probability.’ The date is ad 451, the year in which Aetius won his victory at Chalons-sur-Marne.

Act I. Part of the Roman Forum with the Imperial throne on one side. A view of Rome lit up at night, with triumphal arches and other festive decorations prepared to celebrate the ten-year festivals and to honour the return of Ezio, the conqueror of Attila, who is seen to come forward preceded by warlike instruments, slaves and ensigns of the vanquished, and followed by his victorious Soldiers. Valentinian upon the Throne, Maximus, Varus with the Pretorian Band, Aetius and the Populace. Ezio reports his victory. Valentiniano descends from the Throne, and embraces him, looking forward to his empire rivalling Jove’s. He goes out, attended by Varus and the Pretorians. Massimo embraces Ezio. His daughter Fulvia, promised in marriage to Ezio, enters with Pages and Slaves. Ezio, meeting her, is shocked by the coolness of her greeting. Massimo explains that the Emperor, growing ever more tyrannical and unjust, is now his rival for Fulvia's love, and suggests that Ezio and his army should overthrow him. Ezio is appalled by the idea of treason. Massimo, dissembling, embraces him again.