The action is preceded by a brief prologue, delivered by Apollo. Venus and Cupid are then discovered, in conversation, on a desolate seashore. Venus informs Cupid that Ariadne and Theseus will soon be arriving on the island of Naxos on their way to Athens. They are fleeing from Crete, where the pair have been complicit in the slaying of Ariadne's monster half-brother, the Minotaur, in the labyrinths below the palace of her father, King Minos. Venus has learned that Theseus had decided to abandon Ariadne on Naxos, and to proceed to Athens alone. Cupid offers to rekindle Theseus's passion for her, but Venus has decided to unite her with the god Bacchus, and requests Cupid to arrange this.
Cupid conceals himself, as Theseus and Ariadne arrive on the island a short distance away. Ariadne muses over her disloyalty to her father, but declares her love for Theseus. She departs to find shelter for the night, after which a fishermen's chorus compares her eyes with the stars of heaven. Theseus, alone with his counsellor, discusses his intention to abandon Ariadne, and is advised that this decision is justified, as she will not be acceptable to the people of Athens as their queen.
A chorus greets the dawn as Ariadne, after a troubled night's sleep, returns to the shore with her companion, Dorilla, to find that Theseus has departed. Dorilla offers her comfort; in despair at the thought that Theseus will not return, Ariadne nevertheless decides to go to the landing area to wait for him. In a pastoral interlude a chorus sings of the joys of rural life, and expresses the hope that Theseus will not forget Ariadne. Primed by an envoy with the news that Ariadne is alone and sorrowing, the chorus again sings in sympathy with her. On the beach, Ariadne sings her lament for her lost love and prepares to kill herself. At this point fanfares are heard heralding an arrival, and her hope that it is Theseus returning. In another interlude the chorus expresses hope on her behalf, but a second envoy announces that it is Bacchus who has arrived, having taken pity on Ariadne. A chorus of soldiers precedes the god's appearance, followed by a sung ballo to celebrate the forthcoming betrothal. In the final scene Cupid reappears, and Venus rises from the sea before Jupiter speaks his blessing from the heavens. The union is sealed as Bacchus promises Ariadne immortality in heaven and a crown of stars.