Prince Siegfried, a royal figure, comes upon a crowned swan during a hunt near a lake. He prevents his companion Adolf from shooting it, revealing an instinct to protect. This marks his first connection to the enchanted Princess Odette. Following the swan to a castle, he witnesses her transformation into human form and learns of her curse: by day, the sorcerer Rothbart turns her into a swan, and only a vow of true and everlasting love can free her.

Siegfried shows determined persistence in pursuing Odette. He invites her to his birthday ball, intending to choose her as his bride and break the curse. Though she initially resists due to fear of Rothbart, Siegfried convinces her to attend, demonstrating his resolute and persuasive nature. His feelings for her are immediate and deep, rooted in their first eye contact.

His character faces a critical challenge at the ball when Rothbart and his daughter Odile arrive. Magically disguised as Odette, Odile deceives Siegfried. Under this enchantment, he pledges his love and intent to marry her, unknowingly betraying the true Odette, who witnesses the declaration while restrained by Rothbart. This error stems from magical deception, not faithlessness.

Devastated by the betrayal upon Rothbart's triumphant revelation, Siegfried pursues them back to the enchanted castle, leading to a confrontation. Rothbart gains the upper hand, threatening Siegfried's life. To protect Odette from being forced to marry Rothbart, Siegfried makes the ultimate sacrifice: he seizes Rothbart's sword and impales himself. This act triggers a magical reaction, destroying Rothbart and Odile, breaking all curses, and freeing Odette and the other enchanted swans.

Following the castle's collapse, Siegfried survives and reunites with Odette. Their love, proven through his sacrifice, overcomes the sorcerer's magic. The resolution sees them embracing as the curse lifts and the other transformed characters regain their original forms.