The Secret of Spiggy Holes by Enid Blyton

In Enid Blyton’s classic Secret Stories, mystery always leads to adventure.

Mike, Peggy, Nora and Jack are having a lovely summer at the Cornish seaside. While out exploring the Spiggy Holes caves, they discover a secret passage leading to the Old House on the cliff. But when they encounter the Old House’s horrid new owner, the children are convinced he is hiding some secrets of his own….