Julian, Dick, George (Georgina by rights), Anne and Timothy the dog (the Famous Five) are planning to go camping in a moor with the absent-minded and insect-loving Mr Luffy, a master at Julian and Dick's school. When they arrive at camp they find that their camping site is close to a farm, and that several old train tracks run under the moors, some of them are unused. They soon make friends with a boy named Jock, who lives at the farm with his mother and stepfather, the farm owners. While exploring the moor, the Five find a railway yard and a tunnel that are apparently abandoned. A watchman called Wooden Leg Sam tells them that "Spook trains" travel along those tracks before chasing them away.
