In the woodland lake lives the water nymph Rusalka with her father, the water goblin. She has fallen in love with a Prince and wishes to be a human female. So she asks the witch Ježibaba to change her into a woman. In return, however, she must give her voice. But if her beloved does not remain true to her she will be cursed and he will die. The Prince falls in love with her, too, but after only a week on his castle he is  disappointed: she does not respond to his passionate physical attentions. During the  wedding preparations a foreign princess arrives whom the Prince was always meant to marry. The princess sees her chance and actively offers herself. Rusalka is forced to watch her beloved slipping away. The water goblin takes his horrified daughter  back to the lake. She can only change back into a genuine water nymph if she kills  the Prince. Rusalka refuses. In the meantime, the Prince has obviously gone mad,  comes to the lake and wants her to kiss him. She sadly refuses to comply, since to do so wou ld bring him death. But when the Prince insists, she kisses him.