Ariadne, abandoned by Theseus, longs to forget the feeling of being half of an inseparable being called "Theseus-Ariadne" and prepares herself for Death. The nymphs–Echo, Naiad, and Dryad–mourn her endless days of weeping. Zerbinetta and the commedia actors peep in from offstage, fearing that it will be difficult to lift her spirits.
Singing and dancing, the commedia actors enter. They are joined by Zerbinetta who explains that love is a compulsion; each new lover comes, like a god, to transfigure his beloved.
As if to illustrate the truth of her philosophy, Zerbinetta engages in mock-flirtation with the commedia actors. Finally choosing Harlequin, she retires with him, to the discomfort of the others. The nymphs rush in singing praises to Bacchus, son of Jupiter. They recount his escape from Circe, an enchantress who transforms all her lovers into beasts.
Bacchus enters, calling out in triumph that he has conquered the spell of Circe. Ariadne is awakened by his song. As her longing for Death transforms to love and Bacchus becomes aware of his divinity, passion enfolds them.