The capricious princess mocks the grooms invited by her father, allowing her jester to humiliate their appearance. Angered by the behavior of his daughter, the king orders her to be married off to the first beggar who entered the city. By chance, the "beggar" turns out to be one of the knights rejected by the capricious woman - the prince, who teaches the princess a harsh lesson that changed her attitude towards life.

Rusalochka opens in modern day Copenhagen, Denmark. Several tourists gather around the capital's famous mermaid statue, as a tour guide explains its significance. A fish in the water below the tourists scoffs at their foolishness, and then, proceeds to tell about the doomed love of the mermaid. Upon reaching her 15th birthday, the Little Mermaid is allowed to swim up to the surface above. As soon as she does, however, the Mermaid spots a young prince caught up in a dreadful storm. She admires the man's bravery and decides to save him, declaring that, "The beautiful and the brave should not perish." After the mermaid returns to the ocean, she decides that she wants to become human.