In an old German Castle, Prince Siegfried's birthday is being celebrated: today he comes of age. His mother, the Princess Mother, friends and courtiers, congratulates him. In a majestic ceremony, Siegfried became a knight. From this day, on a sense of duty and valor will be the guiding principles in his life. The last toasts are pronounced in his honor and young girls of his age try to attract his attention, but Siegfried is overcome by emotions of a different order: he dreams of a pure, ideal love. The festivity draws to an end, the guests depart, leaving the prince alone with his thoughts in the gathering dusk. Night falls. Siegfried in conscious of the presence of a shadow at his side, it is as if some mysterious force is beckoning to him. It is the Evil Genius, of Fate itself, who has come to reveal some perturbing secrets to the prince. Submitting to the powerful pull of his invisible companion’s presence and full of anxious foreboding, Siegfried succumbs to the ideal world of his dreams.
Lured by the Evil Genius, Siegfried finds himself on the banks of a mysterious lake. In the shimmering patches of moonlight on the water, visions of bewitched swan maidensrise up before him. Siegfried catches sight of Odette, the most beautiful of the maidens: he is spell-bound, deeply struck by her beauty. At last, he has found his romantic ideal of love. He swears to Odette he will love her forever and be faithful to her.
Prospective brides-to-be are arriving at the Princess Mother's castle. The Prince must choose one of them to be his wife. Siegfried appears: he can think of nothing but Odette and his meeting with her. He dances in an offhand way with the well-born maidens-not one of them can compare to his ideal. Suddenly, a mysterious knight arrives at the ball accompanied by a ravishingly beautiful young girl and a suite of black swans. It is the Evil Genius and Odile, Odette's double. Struck by their resemblance, Siegfried hurries towards Odile. The Evil Genius is putting the Prince’s sentiments to the test. The perfidious Odile who manages to disarm him of all his doubts enchants Siegfried: he announces Odile to be his chosen bride. At this very moment, the throne room is plunged in darkness and a vision of the beautiful Odette appears before the assembled company. Siegfried realizes that he has become a plaything in the hands of Fate. Hoping to atone for his betrayal, he rushes in despair after the receding image of the white swan.
Night time. A deep gloom overhangs the lake. Odette brings the tragic news: the Prince has broken his vow of faithfulness to her. Siegfried's conscience is deeply troubled: he hurries towards Odette begging for her forgiveness. The Evil Genius summons up a storm, which disperses and plays have with the heroes of our tale, making it impossible for them to unire. Made weak by his single combat with Fate, Siegfried tries in vain to hold on to the vanishing image. The Evil Genius is about to do away with the Prince when Odette throws herself between them just in time to save Siegfried. Instantly, their love triumphs over the Evil Genius, to finally bring him down.