Ricky Rapper is a ten year old boy who lives with his aunt Serena and likes to play drums and rap. His aunt breaks her leg, leading to cousin Fanny moving in to take care of the household. Fanny is very strict and that means no more drums for Ricky. With the help of his downstair neighbor Nelly, Ricky seeks to restore the normal order to the apartment.

Ricky Rapper and Nelly Noodlehead leave for the island, where Fanny Rapper works as the resort hostess. At the same time, Uolevi Horsmaniemi arrives with his daughter Wendy, who is little older than Ricky and Nelly. Wendy's arrival confuses the relationship between Ricky and Nelly, as Nelly begins to spend more and more time with Wendy.

Summer vacation has just begun. In honor of it, Serena Rapper and Lennart Lindberg decide to go on holiday. Ricky gets a new bicycle as a consolation, but it disappears mysteriously. Ricky and Nelly Noodlehead go looking for it which turns into a thrilling adventure.