In the castle everybody is celebrating the adulthood of Prince Siegfried. The amusing dances of the Jester alternate with the gracious dances of the young ladies and their partners. There comes the Sovereign Princess who gives her son an arbalest as a present. She tells him that he should choose a wife at tomorrow's ball. Night is drawing on. The young women and men went home. Siegfried is seeing in his dreams the image of the girl with whom he could fall in love. The Jester takes him out of the deep reflection by showing him the swans flying overhead. Siegfried goes hunting.
At the shore of the deep lake are raising the dark ruins of an ancient castle. At midnight, when everything around is deep in sleep over the lake are swimming white swans. Siegfried appears attracted by a magnificent swan illuminated by the moonlight. He aims, but suddenly he loosens the bow struck by the unexpected transformation of the swan into princess Odette. The swan maidens surround Siegfried. Odette reveals to him the secret of the omen hanging over her and her girlfriends. An evil sorcerer transformed them into swans and only at night around these ruins they could regain their human form again. Moved by Odette s sad story, Siegfried proposes to kill the sorcerer. She sadly replies that this couldn t spoil the spell. Only the selfless love of a man who never ever vowed his love before could defeat the malediction. The evil sorcerer who lives at the castle s ruins has overheard the conversation between Odette and Siegfried. He is decided not to release Odette from his power. Siegfried is full of love and pity for the beautiful Odette and invites her to tomorrow s ball where he would declare their engagement. She warns Siegfried that the sorcerer through perfidy and craft shall do his best to make him break his vow of fidelity and if this was to happen she and her friends were going to die. It is dawning. The maidens must transform into swans again. Siegfried is sure in the power and the durability of his feelings - he shall save Odette.
At the ball in the castle Siegfried cannot choose among the maidens his fiancée. He is totally in the power of the memory of the beautiful swan maiden Odette. The sounds of a trumpet are announcing the appearance of the evil sorcerer - Rothbart. He is leading with him his daughter Odile who amazingly resembles Odette. Siegfried decides that she was his fiancée Odette, the swan maiden. The evil sorcerer has ordered Odile to charm Siegfried and to force a declaration of love from him. Fascinated by Odile, the prince doesn't notice the swans flying overhead. He declares to his mother that he has decided to marry Rothbart's daughter. The vow is broken and Odette and her friends are going to die. When the sorcerer points to Odette's image which appeared at the castle's window, Siegfried realizes he was deceived. He is hurrying desperately towards the Swan Lake.
Dark night on Swan Lake's shore. Odette tells her friends about Siegfried's infidelity. The prince comes and assures his beloved one that he hasn't forgotten his vow of love and in the castle he has seen his Odette in the face of Odile. The evil sorcerer is furiously evoking the elements against the lovers. But nothing can break their love and separate them. Feeling he would lose his power, Rothbart destroys his castle in order to block the way of the lovers. The sorcerer perishes in a duel with Siegfried. Odette and Siegfried, surrounded by the maidens, are welcoming the first beams of the rising sun.