Famous Five: Five Go To Billycock Hill

In the sixteenth book of the Famous Five series, the five friends Julian, Dick, Anne, George (Georgina), and Timmy the dog, embark on an adventure to Billycock Hill. It starts off as a peaceful camping trip, but soon they are drawn into a mysterious and thrilling adventure when they learn about the disappearance of some top-secret military aircraft and the involvement of their friend Toby's cousin, Jeff, a pilot. The Five must solve the puzzle of the missing aeroplanes and clear Jeff's name in a tale of bravery and friendship.