'The bolt was securely pushed home. So somebody was a prisoner on the other side!'
George has joined her cousins for an exciting caravanning holiday, where there;s a ruined castle on top of a hill nearby. Keen to explore it, the Five make plans to visit. But when they spot a desperate face in the tower window, they know there's a mystery solve ... Who is hiding inside the castle - and why?
This softback book written by Enid Blyton with inside illustrations by Eileen Soper was originally published in Great Britain in 1952. This edition was published in 2016.