At first, the Famous Five can't believe that Tinker, a quirky young boy, with a pet monkey called Mischief – owns a lighthouse, on Demons Rocks! But then, when he offers to take them to spend the holidays, there – this extraordinary fantasy becomes an exciting reality – and they become involved in an adventure of undersea tunnels, a treasure trove of gold coins, and some ruthless villains, prepared to do anything to claim the fortune stored beneath the Lighthouse. The Famous Five and Tinker need to tell the Police: but then, they find themselves locked within the walls of the Lighthouse...
