At home, the three siblings Katja, Kenny and Kurt don't have much money, and this is going to be a boring summer vacation. Katja really wants to go camping with her friends from the dance team, but her mother Annisette can't afford it. Fortunately, the situation changes when the children's grandmother, who goes by the name of Miss Money, gets out of prison. Because Miss Money needs their help to get her hands on the world's largest diamond ring, which she once stole from an evil diamond dealer. The ring is hidden in the Roller Coaster on the Hill, and to get it, the family must come up with a plan that takes them on a thrilling mission with the diamond dealer's henchmen right on their heels..