The Palace Courtyard, late afternoon.
It is Prince Siegfried’s 21st birthday. Young people have gathered to celebrate the occasion, including the Prince’s friend Benno and Wolfgang, his old tutor. The festivities are spirited and there is much dancing and games. In the midst of the activity the Prince’s mother arrives to remind her son that his coming of age is a serious affair – it is a time for him to marry. A ball has been arranged for the following evening and there, from a group of prospective fiancées, he is to choose a bride. Siegfried is disconsolate at the thought of his carefree youth slipping away. He has no desire to marry. The day draws to a close and in an attempt to cheer his friend, Benno points to a flock of wild swans in flight and suggests a hunting expedition. Deciding that the night is still to be enjoyed, Siegfried orders pursuit.
By the lake – evening.
The hunting party follows the swans through the woods, reaching a clearing where they have settled on a nearby lake. Siegfried’s attention is suddenly attracted by a beautiful white swan which is transformed into a lovely young maiden. She is Odette, Queen of the Swans. The evil sorcerer Von Rothbart holds her under his spell – by day she and her friends are swans, and swans they must remain, except between midnight and dawn when they may resume their human form. Only the pure love of a young man can remove the curse. Astonished by her beauty and full of love for Odette, Siegfried’s love will destroy Von Rothbart’s power. Von Rothbart suddenly appears in the form of an owl, beckoning menacingly to Odette. As dawn breaks, the lovers bid farewell. Odette returns to the lake, resuming her guise as a swan, and Von Rothbart plots to make the Prince break his vow.
The Castle Ballroom – the following evening.
The entire court is assembled for Siegfried’s betrothal ball, the invited princesses and the their families eagerly awaiting the decision of the Prince. The Prince’s mother indicates he is to choose a bride from the maidens present, but none pleases him. The young Prince’s mind is still filled with images of the beautiful Odette. Mindful of his vow of fidelity, he pays little attention to the eligible young women with whom he is presented. Suddenly, a fanfare announces the arrival of two new guests. It is Von Rothbart, disguised as a nobleman, and his daughter Odile. The Prince stands transfixed by her likeness to Odette and, overwhelmed by the unexpected appearance of his true love, he asks her to dance. Odile so bewitches the Prince that he asks for her hand in marriage. Convinced that he is with his beloved Odette, he declares his fidelity in front of all present. Triumphantly, Von Rothbart and Odile reveal themselves. The Prince realizes too late that he is a victim of their cruel treachery. Odette has been betrayed, and now can never be released from her enchantment. In despair, the Prince runs to the lake to search for her.
The lake – later that evening.
The swan maidens are anxiously awaiting Odette’s return when she runs in and tells them in anguish of Siegfried’s betrayal. The evil magician has triumphed, and there is no salvation for the swan maidens now. A storm springs up on the lake. The Prince comes running to the lakeside and begs Odette to forgive him, but Odette is destined to die. The Prince fights with Von Rothbart; in his last effort the swan maidens are freed from his evil spell, and the souls of Siegfried and Odette are united in eternal happiness.