Act I
On a moonlit night, in a meadow by the lake, the wood nymphs are dancing and playing with the Water Sprite, who pretends to try to catch them. As they leave, Rusalka tells the Water Sprite of her love for the prince whom she often sees by the lake. She wishes to become human and to have a soul. Horrified, the Water Sprite gloomily tells his daughter of the consequence of becoming human. He sends her to the witch, Jezibaba, to ask for help and advice. Jezibaba tells Rusalka that the price of becoming human is very high: Rusalka must remain mute, and if she does not succeed in keeping the prince’s love, she must return as a spirit to the waters, where she will lure her love to his death, while she remains condemned forever.
As the sun rises, the prince, out hunting a white doe, feels sinister magic in the woods, and tells the other hunters to leave. He meets Rusalka, who has been transformed into a lovely maiden, and is enchanted by her beauty. Unable to speak, Rusalka throws herself into the prince’s arms. He carries her off to his castle as the water sprites sing of the loss of their sister.
Act II
At the castle, the gamekeeper and the cook gossip about the upcoming marriage of the prince to the strange speechless maiden he has brought home from the woods. They are glad that the prince’s interest in the strange maiden is already waning, and that his attention is turning towards a foreign princess, with whom his country is in political negotiations.
The prince enters, asking a sad Rusalka why she does not burn with the passion he feels. When the foreign princess talks seductively to the prince, Rusalka realizes the threat to her happiness, and runs back to the woods, where she speaks with her father of her fear of loss. Her father advises her to persevere, but Rusalka is no match for the aggressive princess, who soon has enticed the fickle prince with her charms. As the prince rejects Rusalka, the Water Sprite appears and carries Rusalka off with him to the lake. The frightened prince appeals to the princess, who laughs at him cruelly and departs.
Act III
Rusalka enters into a frozen landscape, speaking of her sorrow, when she reencounters Jezibaba. She tells the sad young creature that in order to wash away the curse she must now kill the prince. Rusalka is unwilling to consider this, and becomes a water spirit.
Frightened, the gamekeeper and the cook have come to the woods to ask Jezibaba for advice about the prince, who has fallen ill, cursed by some strange spell. The Water Sprite, who is asleep not far from them, wakes up and chases them away, cursing the human race.
The prince enters like a madman crying out for Rusalka and calling upon heaven and earth to help him find her. Appearing as a spirit in the moonlight above the lake, Rusalka speaks to the prince, kisses him, and he dies blissfully.