A lost emerald, a mysterious castle, a curious traveling circus, and then Dick is kidnapped. A thrilling adventure as the Famous Five attempt to solve a legendary mystery.
The summer holidays are just around the corner and their bags are packed - George, Julian, Dick, Anne, and Timmy set off on a bike ride to the legendary Cat Canyon. In the 19th century, the "Black Cat" is said to have saved the world's largest emerald, the "Green Eye," from thieves here before hiding it. And it is yet to be discovered to this day. And so the adventure begins: The Famous Five meet Hardy, who is the same age as them. When riding on his quad bike, Dick is mistaken for Hardy - and kidnapped by two gangsters. With Hardy's help, George, Julian, Anne and Timmy set off in pursuit. The trail leads them to a curious traveling circus and a mysterious medieval castle, where Dick is being held captive. Here the Famous Five discover the evil intentions of the dastardly leader of the gang of crooks. A fearless race to the mystical caves ensues.