Hurrah! It's holiday time, and the Famous Five are spending it at Billycock Hill. Most exciting of all, they've made a new friend - a real pilot! But now he has disappeared, with top secret equipment . . . The Five are puzzled, and concerned, too. Could their new friend by a spy - a traitor! Whatever his motives are, the gang feel duty-bound to investigate . . . These classic editions feature Enid Blyton's unchanged text and Eileen A. Soper's original illustrations.