It's the story of four children: Julian aged 12 , Gorge aged 11 ( short for Georgina because she would like to be a boy ) ,Dick aged 11 and Anne aged 10 and a dog, Timmy. They find a secret passage that goes from Kirrin cottage to Kirrin farm. The children have a tutor - Mr Ronald. A few days later the children' s uncle sees that three pages of his extremely important plans for his new invention have disappeared...

Julian, Dick and Anne arrive in Kirrin Cottage to stay with George (real name Georgina) for the holidays. They plan to spend time exploring Kirrin Island but their happiness is spoilt when Aunt Fanny falls ill and has to leave with Uncle Quentin to be treated in a far-off hospital.

The FAMOUS FIVE are Julian, Dick, George (Georgina by right), Anne, and Timothy the dog. This is the story how the 'Famous Five' came into being, and of their very first adventure together. And what an adventure it was-involving an island, a ruined castle, an ancient wreck-and a desperate treasure hunt! The children's pluck and resourcefulness saved the family fortunes and made possible many more exciting expeditions for the Five.