The Persian king Serse is betrothed to Amastre; yet on his adventurous military campaign to Greece, the conquests he seeks to make are above all amorous in nature. Serse’s brother Arsamene is conducting a secret liaison with Romilda, the daughter of his commander, Ariodate. The king learns of this, immediately falls in love with her, and bids his brother of all people to act as Serse’s marriage broker. Arsamene resists, and Serse banishes him. Romilda’s sister Atalanta sees in this situation an opportunity to win Arsamene’s love for herself, and pressures Romilda into yielding to the king’s suit. Yet Romilda refuses, and Arsamene, who has gone into hiding, fights for his beloved with the assistance of his servant Elviro, whom he sends into the fray dressed as a female flower seller. For her part, Amastre disguises herself as a soldier in order to confound the wilful power games of the king, whom she desires despite his unfaithfulness.
Letters are intercepted and sent to the wrong recipient; intrigues and confusions of love taken to extremes; suicides prevented; the pontoon bridge between Asia and Europe destroyed by a storm; many promises made; accusations levelled, and death sentences passed. Serse eventually falls into his own trap and sees himself forced to grant peace to the hearts of all.