For their bicycle tour to Catmoor, the friends Julian, Dick and Anne, their cousin Georgina, called George, and her dog Timmy have long looked forward to. But the camping holiday in the countryside ends with the kidnapping of Dick, confuse the two underprivileged hoodlums with the same age millionaire's son Hardy. With sophistication and courage, the five friends take on his trail that leads from a mysterious traveling circus to the castle "Owls Nest" where the kidnappers force Dick to coax the clue to a giant emerald.