ACT 1
The opera opens in a meadow by a lake. On a moonlit night, wood nymphs are dancing and playing with Vodnik, who pretends to try to catch them. As they leave, Rusalka tells Vodnik, her father, of her love for the prince, whom she often sees by the lake. She wishes to become human and have a soul. Horrified, Vodnik tells his daughter of the gloomy consequences 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.
As the sun rises, the prince, while hunting the 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 he is enchanted by her beauty. Unable to speak, Rusalka throws herself into the prince's arms. As he carries her off to his castle, the water sprites mourn the loss of their sister.
ACT 2
At the castle, the gamekeeper and the kitchen boy 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.
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. She speaks with her father about her fear of losing the prince. 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. When the prince rejects Rusalka, Vodnik appears and carries Rusalka off to the lake. The frightened prince appeals to the princess, who laughs at him cruelly and departs.
Act 3
By the moonlit lake, Rusalka sits alone, speaking of her sorrow. Hobbling out of her cottage, Jezibaba 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 disappears into the lake.
Frightened, the gamekeeper and the kitchen boy come to the woods to ask Jezibaba for advice about the prince, who has fallen ill, cursed by some strange spell. Vodnik rises out of the lake and chases them away, cursing the human race.
The prince enters, 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, who rushes into her arms. Rusalka kisses him, and he dies as she sinks back into the water.