Five Go to Billycock Hill (The Famous Five #16)
Author: Enid Blyton
Goodreads Rating: 3.94
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 be a spy - a traitor? Whatever his motives are, the gang feel duty-bound to investigate...