Swan Lake

Prince Siegfried, hunting by a lake, falls in love with Odette, a princess turned into a swan by the sorcerer Von Rothbart's curse, which only a vow of eternal fidelity can break. At a court ball, Rothbart tricks Siegfried into declaring his love for Odile, the sorcerer's daughter disguised as Odette's double, causing Siegfried to unwittingly break his vow. Grief-stricken, Siegfried returns to the lake to beg Odette's forgiveness, but the betrayal cannot be undone, and the two are united only in death (or, in some productions, are reunited and Rothbart's power is destroyed, allowing the lovers a happy ending).