Odette and Derek's planned rendezvous at a royal ball is ruined because they didn't realize there was no moon that night; thus, she cannot regain her human form. Derek mistakenly makes a vow of love to the sorcerer Rothbart's henchwoman, who is disguised as Odette.
Derek rushes to the lake to save Odette, who is human again but dying, and finds himself forced to battle Rothbart in the latter's "great animal" form. He manages to kill the monster, and as he professes his love to Odette, she revives. They are wed.