The Queen enters in a ceremonial procession and expresses to Siegfried her wish that he marry. Her insistence, however, only serves to deepen the Prince’s melancholy and reinforce the sense of estrangement he feels from court society. His friend, Benno, attempts to raise his spirits in a series of lighthearted dances with the Fool and the Wench, but they have little effect. Benno's efforts are followed by more dances involving the knights and the Wench, which begin as mere diversions, but grow increasingly unsettling and violent.
When Benno sees a flight of swans, he urges Siegfried to follow him so that they might hunt the birds. Eager to escape the brutality and unpleasantness of the court, the Prince leaves with Benno.
Suddenly Rothbart appears. With him is another princess, a mysterious figure in black named Odile. Siegfried believes Odile to be none other than his beloved Odette and after she dances for him, he chooses her to be his wife. This unwitting betrayal of Odette brings catastrophe upon the court, which is engulfed in a flood. Siegfried is the only one to survive.
– John Reardon
Taking a solitary walk by the lake, the young Princess Odette encounters the evil Von Rothbart. Overcome with fear, she turns and runs in the hope of escaping his power. Von Rothbart catches her and casts a spell on Odette, transforming her into a swan.
It is Prince Siegfried’s twenty-first birthday and courtiers and peasants have gathered to celebrate his coming of age. During the festivities, toasts are made and a pas de trois is danced in the prince’s honor. The queen mother arrives and presents her son with the gift of a crossbow. She informs him that as the time has come for him to marry, she will hold a ball the following evening, to be attended by young princesses from across Europe. The prince is to select the one who pleases him most.
Siegfried is morose, distraught that he cannot marry for love. As the revelers disperse, a flock of swans flying overhead catches the prince’s attention. He reaches for his crossbow and heads out alone into the night.
At the lakeside, the prince encounters a magnificent flock of swans. He aims his crossbow but is startled when one of the swans is transformed into a beautiful woman. It is Odette, Queen of the Swans. Captivated by her soulful countenance, the prince approaches her. She is frightened and turns from him. When Siegfried assures her that he means no harm, Odette reveals to him that she and her companions have been placed under a spell by Von Rothbart. By day they are condemned to take the form of swans and only at night can regain human form. This spell can be broken only if a man promises his love and remains faithful to that vow. As soon as she has confided in the prince, Von Rothbart appears. Siegfried seizes his crossbow and takes aim, but Odette shields the evil enchanter, for if he should die the spell imprisoning her could never be broken. Von Rothbart escapes, drawing Odette away.
The flock of swan maidens dance a beautiful waltz. Siegfried returns, seeking Odette. She appears, and they express their tragic love in a pas de deux. When dawn begins to break, the pale light tells the maidens that they must again change back into swans. Left alone with Odette, Siegfried declares his eternal devotion. Odette bids him a tender farewell and reluctantly reassumes her enchanted form.
Guests assemble for the great ball in which Prince Siegfried is to find his bride. The queen mother and the prince appear, and five prospective fiancées (Spanish, Hungarian, Neapolitan, and a pair of sisters from Russia) present their national dances for the prince. Siegfried’s thoughts remain with Odette, and he informs his mother that he will not marry any of them. At the same moment, trumpets sound the arrival of two additional guests. They are Von Rothbart and his daughter Odile, whom he has transformed into a semblance of Odette. Siegfried is enraptured, convinced he has found Odette again. Siegfried and the beguiling Odile begin the exultant Black Swan pas de deux. During their dance, the real Odette appears as a vision, but Siegfried, enthralled by Odile doesn’t see her, and Von Rothbart spirits her away. At the conclusion of the dance, Siegfried declares his love for Odile and his desire to marry her. The Queen expresses her approval, but Von Rothbart demands that Siegfried swear a formal oath. The prince innocently complies, and when he has done so, Von Rothbart and Odile mockingly reveal their true identities. Siegfried now sees the vision of the weeping Odette and understands his mistake. Frantic, he flees the palace in search of his beloved.
The swans are grieving for their queen. With Siegfried’s broken vow, Odette’s hopes for love and freedom have vanished. Distraught, the prince enters and explains to his beloved that he, too, was betrayed by the evil magician. He begs Odette’s forgiveness and explains that he could never love another. Odette understands and forgives him. Nevertheless, the fatal error condemns her to remain a swan. Instead she determines that she will die. Von Rothbart endeavors to drive Siegfried away and keep Odette for himself, but the lovers defy him. Odette flings herself into the lake and Siegfried follows. Siegfried’s and Odette’s steadfast love breaks the enchanter’s spell and Von Rothbart, too, collapses and dies. With the curse removed, the lovers’ spirits take flight and are reunited for eternity.