The amusing adventures of the young builder Pasha Gusarov began from the moment when he met and fell in love with Katya on the train, who was going to conquer Moscow. Happiness makes a person careless, and the station is just the place where you can lose it. But it is at the station after all kinds of adventures that they meet again and now they will never part.

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.