Eurydice laments her forthcoming marriage to Arideus (Sventurata, che fo?). The chorus warns her of the monstrous savages that lurk in the wood (Ferma il piede, o principessa), but the despairing Eurydice tells them that she is ready to die on the pyre that has been prepared for her (Che chiedete da me?). She compares her cruel fate to that of the abandoned Philomena (Filomena abbandonata).

Orpheus calms the savages, first by playing his harp, then by singing of his love for Eurydice (Cara speme). The savages release their victim, and Orpheus and Eurydice sing of their love for each other. A chorus of male voices praises harmony and humanity (O poter dell'armonia!).

Creon, Eurydice's father, is persuaded to allow his daughter to marry Orpheus rather than Arideus. Creon muses on the tyranny of the emotions (Il pensier sta negli oggetti).

Creon gives Orpheus and Eurydice his blessing. The lovers sing of the joy that fills their hearts (Come il foco allo splendore); nothing can destroy their love (Né la sorte, né la morte).

A chorus of Amorini extols the pleasures of love (Finché circola il vigore); Orpheus and Eurydice join them. A sound of war is heard, and Orpheus goes to investigate, reassuring Eurydice that he will soon return. Left to face the danger alone, Eurydice is terrified.

Eurydice is almost captured by one of Arideus's men. As she cries for help, a snake bites her. She calls Orpheus, but he cannot hear her; she dies alone, singing of her love for him (Del mio core il voto estremo).

Orpheus finds Eurydice's lifeless body and is overcome with grief and rage (In un mar d'acerbe pene).

Creon hears of his daughter's death. In a fury, he cries out for vengeance (Mai non sia inulto)

A chorus mourns Eurydice (Ah, sposo infelice!) and Orpheus and Creon grieve together (Al cielo te ne voli).

Creon wonders what will become of Orpheus now that he has lost his beloved Eurydice, for life without love is meaningless (Chi spira e non spera).

Orpheus consults the Sibyl, who reveals herself to be the Spirit of Love (Genio), who promises to lead him to the underworld to search for Eurydice. The Sibyl tells him that he will soon find happiness if he is able to temper his desire with constancy and valour (Al tuo seno fortunato).

Orpheus is overjoyed. He will not fear the terrors of the underworld if he can see Eurydice again, even if only for a single moment. A chorus extols justice and righteousness (La giustizia in cor regina) as he follows the Sibyl.

In Hades, on the shores of the river Lethe, the Sybil leads Orpheus past a chorus of unhappy shadows (Infelice ombre dolenti) and a horde of howling Furies (Urli orrendi, disperati).

Orpheus asks Pluto's mercy. Impressed by Orpheus's love for Eurydice, Pluto grants him permission to search for her in the Elysian fields.

Orpheus finds Eurydice. Genio warns Orpheus that if he looks at his wife, he will lose her for ever; but he cannot resist glancing at her.

Orpheus loses Eurydice for a second time (Perduto un' altra volta). Tormented by grief, he longs to die (Mi sento languire, morire me sento).

Orpheus's grieving is interrupted by a chorus of Bacchantes praising love and pleasure (Vieni, vieni, amato Orfeo). Orpheus renounces the pleasures of the world. The Bacchantes offer him a drink, telling him that it will make him happy (Bevi, bevi in questa tazza). He drinks from the cup and realizes that he has taken poison; he collapses and dies. The Bacchantes set off for the island of pleasure (Andiamo, amiche, andiamo), but a storm arises and they drown.