Act 1
In the hall of a Scottish farmhouse, James Ruben, a young Scotsman, sleeps in a chair by the fireside. A sylph gazes lovingly upon him and dances about his chair. She kisses him and then vanishes when he suddenly wakes. James rouses his friend Gurn from sleep, and questions him about the sylph. Gurn denies having seen such a creature and reminds James that he is shortly to be married. James dismisses the incident and promises to forget it.
James' bride-to-be, Effie, arrives with her mother and bridesmaids. James dutifully kisses her, but is startled by a shadow in the corner. Thinking his sylph has returned, he rushes over, only to find the witch, Old Madge, kneeling at the hearth to warm herself. James is furious with the disappointment.
Effie and her friends beg Old Madge to tell their fortunes, and the witch complies. She gleefully informs Effie that James loves someone else and she will be united with Gurn. James is furious. He forces Madge from the hearth and throws her out of the house. Effie is delighted that James would tangle with a witch for her sake.
Effie and her bridesmaids hurry upstairs to prepare for the wedding, and James is left alone in the room. As he stares out the window, the sylph materializes before him and confesses her love. She weeps at his apparent indifference. James resists at first, but, captivated by her ethereal beauty, capitulates and kisses her tenderly. Gurn, who spies the moment from the shadows, scampers off to tell Effie what has happened.
When the distressed Effie and her friends enter after hearing Gurn's report, the sylph disappears. The guests assume Gurn is simply jealous and laugh at him. Everyone dances. The sylph enters during the midst of the revelry and attempts to distract James.
As the bridal procession forms, James stands apart and gazes upon the ring he is to place on Effie's finger. The Sylph snatches the ring, places it on her own finger, and, smiling enticingly, rushes into the forest. James hurries after her in ardent pursuit. The guests are bewildered with James' sudden departure. Effie is heartbroken. She falls into her mother's arms sobbing inconsolably.