Five Go Off to Camp: Spook trains in the dead of night! And they seem to vanish into thin air - but where do they go? The Famous Five are on to it! But discovery of an unusual underground tunnel system, and a secret train-service, has them puzzled. If they follow the tracks, will they solve the mystery? Five Go to Billycock Hill: 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 ...