A Scottish manor house.
It is the morning of James’s marriage to Effie and he is asleep in his armchair. A winged figure, a Sylphide, is kneeling by his side. She kisses him on his forehead and he wakes up confused. Entranced by the vision of the Sylph, he attempts to capture her, but she escapes him; as she reaches the fireplace, she vanishes up the chimney. Troubled, he wakes his companions but none of them have seen her. Gurn, James’s rival, arrives and learns that James is infatuated with someone other than Effie.
The preparations for the wedding are in full swing. James hardly notices Effie; instead she is wooed by Gurn whom she ignores. James joins in the preparations but gradually realizes that, as Effie dreams more and more of the wedding, his own dreams go far beyond the walls of the manor house.
An old woman, Madge, has slipped unnoticed into the hall to warm herself by the fire. James, sensing that she is a sinister presence, takes an immediate dislike to her and cannot bear to see her sitting where he last saw the Sylph. He orders her to leave but Effie calms him and persuades him to let Madge tell the fortunes of some of the guests. Madge prophesies that Effie will marry Gurn, and James, furious at this, threatens Madge, who curses him. Effie runs off to dress for the wedding leaving James alone and in turmoil.
The Sylph once again shows herself to James, declares her love for him and tells him that they belong together, Gurn enters and, believing that he may have caught James talking to another woman, attempts to reveal the situation to Effie but fails.
As the wedding festivities begin, the Sylph reappears and, unable to resist her enticements, James follows her into the forest. Effie is left broken-hearted.
A glade in the forest.
Deep in the forest, shrouded in mist, Madge is planning her revenge. She makes a veil, irresistible to all in a magic cauldron. As the fog lifts, James enters with the Sylph, who shows him her realm. She brings him berries and water but evades his embrace. To lift his spirits she calls on her sisters and the forest fills with sylphs, who dance for James. Try as he might, he is unable to catch the Sylph in his arms.
Effie and James’s companions reach the glade looking for him. Gurn finds James’s hat, but Madge convinces him to say nothing. He proposes to Effie and, encouraged by Madge, she accepts. Everyone leaves to prepare for the wedding of Effie and Gurn.
Meanwhile, James is desperately looking for the Sylph, and Madge convinces him that the veil she has made will enable him to catch her. The Sylphappears and, seeing the veil is totally captivated by it. She allows James to place it around her shoulders and as he does so, he kisses her. His embrace is fatal and the Sylph’s wings fall to the ground. In despair James sees what should have been his own wedding party in the distance. As Madge forces him to see what he has lost, he realizes that in trying to possess the unobtainable he has lost everything.