In the kingdom of Vodník a strangely mysterious theatrical family has gathered: the melancholic and, at the same time, irascible Vodník, the omniscient and feared Ježibaba, the nymphs of the forest, who float above the stage like dancers, and finally, Rusalka, Vodník's favorite daughter, who desires nothing more ardently than to be able to float through the air like her dancing sisters. But to this world of illusions and dreams also belong idealistic jokers and clowns, and perhaps many of these dreamers have already failed. The kingdom of Vodník is a world of fantasy, but also one of disappointments. Worse still, Vodník, who hates human beings, does not allow his daughters to leave his world.
Rusalka longs for a different life, a real life, in which she can belong to a man, become a beloved woman, and possess a soul that then rises higher, all the way to heaven, after having lived a full life. She yearns for love and begs Vodník to set her free. He had always feared that he would not be able to keep Rusalka bound to him forever. Like a deluded lover, he disowns his daughter and wishes her every conceivable misfortune.
Her stepmother Ježibaba now sends her into the world and she also predicts that she will fail on her life path. Like a witch in a story, she casts a curse before she leaves: first she will lose her speech and then, if she finds a man who loves her, and he is not faithful to her, he will have to pay for the infidelity with his life. Rusalka, however, continues her unflappable path: she believes in love and in the power of an innocent soul. Now it can float and dance like a feather. And just as she had imagined in her most beautiful dreams, a young man loses himself within her world and takes her with him, away from a childhood that seemed so protected, but has increasingly turned out to be a prison. The freedom and happiness that love provides seem to be within reach. Rusalka is, in fact, speechless due to her happiness.
The young man is a prince and has taken Rusalka to his castle. A week after their first meeting, he already wants to marry her. The bridal party is quickly organized. But all of this is so precipitated that Rusalka can barely comprehend her fate and still cannot regain her speech. She constantly has the feeling that she is not worthy of the prince, and the prince, shortly before the wedding, also feels deeply insecure and does not know if this strange silent creature will make him happy. He wants her to match his passion with clearer signs. But Rusalka does not know the games of love well and is silent.
A foreign princess, who has been invited to the wedding, recognizes the prince's doubts and also perceives that he can be easily tempted. She mocks him for having a silent and mysterious fiancée, and finally sets out to seduce the groom in the presence of his fiancée. Rusalka, who had believed in the goodness and sincerity of people, and especially in the word and love of the prince, must admit that Vodník was right. He has mingled with the guests and watches his daughter fail in the great and vast world, exactly as he had predicted. Rusalka, on the contrary, reproaches her father for being the one responsible for her not being able to give herself to the prince. She must have inherited his coldness as a dowry. Also, Ježibaba's curse begins to take effect. When she sees how the prince betrays his oath of love in front of her eyes by meeting the foreign princess, all her illusions are shattered. Her dream of a love affair with the prince has been shattered.
Rusalka is homeless. She returns to her family, but she knows that her father will never take her in again. And when Ježibaba advises her to kill the prince - because with it she could free herself from the curse and regain her happiness - she definitively denies the kingdom of Vodník. She would rather live without being released than to kill the man she still loves in revenge. The spirit world now welcomes the restless Rusalka. Vodník mourns with the dancing nymphs the loss of daughter and sister. But Rusalka meets the prince again in the new spheres in which he has entered. In the same way that her spirit slowly dissolves in the pain of love, the same happens to the prince's: from the bad conscience of having betrayed Rusalka. He has denied human beings and civilization and wants to be united with it. When the two meet again, Rusalka is able to speak to him for the first time. And they both try to express themselves clearly and understand why their love was doomed.
She can finally forgive him and kisses him. With this kiss of forgiveness, she ends the curse of her parents and that of the false world that weighed on him. Rusalka has understood that love and guilt, beauty and pain, are intertwined. Now, with his kiss, he can free the prince from the suffering of the world. She prays to God to have compassion on human beings.