Julian Dick and Anne are surprised when they can't go to the house in Polseath and end up in Kirrin cottage. Aunt Fanny is lovely but Georgina wants to be a boy and Uncle Quentin is a mad scientist! The children soon made friends and the five (including Timmy the dog) set off on an adventure!
When Dick gets kidnapped after being mistaken for a boy named Richard, the others set out to rescue him and soon find themselves involved with desperate criminals, stolen diamonds, and escaped convicts.
Uncle Quentin hires a tutor, Mr Roland, to teach the children during the holidays. Meanwhile, the Five find a secret panel at Kirrin Farmhouse, some of Uncle Quentin's papers go missing, and there are two strange artists staying nearby.
Julian, Dick and Anne are really worried-George and her devoted Timmy have just disappeared. Not only that, somebody has broken in to Kirrin Cottage. Could there be a connection? The Famous Five think so, but it's going to be tough getting to the bottom of this mystery.
When the Five decide to spend the holidays in their friend Tinker's lighthouse, they soon find themselves thrown into another adventure, this time involving secret tunnels, hidden treasure, and being trapped in a storm-battered lighthouse.
Berta, the daughter of Uncle Quentin's friend is in danger. She stays with the five at Kirrin Cottage, where they are confined for her safety. George is mistakenly kidnapped, and Julian, Anne, Dick and Jo, set out to rescue her.