Farnace and Sifare, sons of the mighty warrior Mitridate, both love their father's fianc�e Aspasia. While Sifare is determined to remain loyal to his father, Farnace vows never to yield.
Mitridate discovers that Farnace is preparing to betray him to their enemies, and that Sifare and Aspasia love each other. He swears vengeance on them all, and marches into battle. Sifare and Farnace escape their imprisonment to join him. Mitridate dies from his wounds, finally reconciled with his family.