Warning - the following contains spoilers about the plot
ACT 1
The water sprite Rusalka has fallen in love with a human—the Prince—when he came to swim in her lake. Now she wants to become human herself and live on land to be with him. Rusalka’s father, Vodník the water goblin, is horrified and tells her that humans are evil and full of sin. When Rusalka insists, claiming they are full of love, he says she will have to get help from the witch Ježibaba.
Rusalka calls on the moon to tell the Prince of her love and then implores Ježibaba for help. She agrees to turn Rusalka into a human—but warns her that if she doesn’t find love she will be damned and the man she loves will die. Also, by becoming mortal, Rusalka will lose her power of speech. Convinced that her feelings for the Prince can overcome all spells, Rusalka agrees and Ježibaba gives her a potion to drink.
As dawn breaks, the Prince appears with a hunting party and finds Rusalka by the lake. Even though she can't speak to him, he is captivated by her beauty and leads her away to his castle. From the lake, the voices of Vodník and the other water sprites are heard, mourning the loss of Rusalka.
ACT 2
The Prince demands to know why Rusalka is so cold towards him, though he remains determined to win her. A Foreign Princess, who has come for the wedding, is intent on winning the Prince for herself. She mocks Rusalka’s silence and reproaches the Prince for ignoring his guests. The Prince demands Rusalka dress for the ball and escorts the Princess into the castle for the beginning of the festivities. Disconsolate, Rusalka falls into a disturbed sleep.
Vodník appears and sings of his grief at losing Rusalka. When she begs her father to help, telling him that the Prince no longer loves her, Vodník has little to offer. The Prince enters with the Princess and confesses his love for her.
When Rusalka intervenes, rushing into his arms, he rejects Rusalka. Vodník warns the Prince of the fate that awaits him, then disappears into the watery depths with Rusalka. The Prince asks the Princess for help but she ridicules him and tells him to follow his bride into hell.
ACT 3
Rusalka waits by the lake once again, lamenting her fate. Ježibaba mocks her, then hands her a knife and explains that there is a way to save herself: she must kill the Prince. Rusalka refuses, throwing the weapon into the water and sinks into the lake in despair.
The wood sprites enter, singing and dancing, but when Vodník explains to them what has happened to Rusalka, they fall silent and disappear.
The Prince, desperate and half crazy with remorse, emerges from the forest, looking for Rusalka and calling out for her to return to him. She appears from the water, reproaching him for his infidelity, and explains that now a kiss from her would kill him. Accepting his destiny, he asks her to kiss him to give him peace. She does, and he dies in her arms. Rusalka asks for mercy on his soul and disappears into the water.
Adapted from The Metropolitan Opera