Julian, Dick, Anne, George and Timmy the dog find excitement and adventure wherever they go in Enid Blyton's most popular series. In book sixteen, it's holiday time at Billycock Hill and the Famous Five make new friend - a real pilot! But when he disappears with top secret equipment, the Five begin to wonder if their new friend could be a spy, or worse, a traitor. Whatever his motives, the gang feel duty-bound to investigate... The text in this edition has been sensitively edited for today's reader and is unillustrated.