Summer holidays are finally here! The Famous Five, George, Julian, Dick, Anne and their dog Timmy set out on their first journey by bike on their own – unaccompanied by parents. On camping the kids encounter a strange boy named Hardy. They try to get rid of this annoying kid, but then Dick is kidnapped! He is a victim of confusion, as our Famous Five discover promptly. The Hijackers have it rather in for Hardy, who s the son of business tycoon Kent. Do they want ransom? With their good deal of detective instinct the kids are able to find the place where Dick has been abducted to: a medieval castle, called “Owl Nest”. George, Julian, Anne and Timmy get support from Hardy who is gradually proving to be a real help. At “Owl Nest” the kids figure out, that the dastardly thugs are hunting for legendary “Green Eye” in fact, the most valuable jewel of the world. Without even knowing it, Hardy is bearing secret hints about the ultimate destination of the jewel. A wild chase for the smaragd starts, leading our Famous Five to a mysterious travelling circus and deep into the adventurous caves at “Graffenstein” rock…