As Ariadne, forsaken by her beloved Theseus, gives herself over to her pain, the three nymphs Naiad, Dryad and Echo struggle to keep their composure. Awakening from an uneasy sleep, Ariadne seeks in vain to banish the memory, now a torment, of her love for Theseus. She is observed by a group of former theatrical entertainers, including Zerbinetta and Harlequin. Harlequin seeks to raise the lady’s spirits with a song but only intensifies her longing for Hermes, the messenger of death, who shall liberate her from the world. The troupe then tries to console Ariadne with an old number – to no avail. Zerbinetta sends the men away. She wants to be alone with Ariadne, whose pain she understands from her own experience. The intimacy that develops between the two women despite social barriers is shattered by Harlequin, who prevails over the other men by exploiting Zerbinetta’s dependence. The nymphs are relating the fate of the young Bacchus when he suddenly appears. He narrowly escaped the erotic enticements of the sorceress Circe. Now he approaches Ariadne in a state of profound confusion, suspecting her to be a sorceress as well. She first believes that Theseus has returned to her and then mistakes him for Hermes, herald of death. That misunderstanding allows the two to come together, leading to a mutual transformation: Prepared to die, Ariadne discovers in Bacchus’s arms a renewed capacity for love, while Bacchus becomes a man.