Julian, Dick, Anne, George and Timmy the dog find excitement and adventure wherever they go in Enid Blyton's most popular series.

In book 16, it's holiday time at Billycock Hill, and the Famous Five make a 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....