Publisher's Synopsis
Book 3 of 17 in the bestselling standalone middle grade mystery series!
★★★★★ Over 4,000 five star series reviews/ratings on Amazon and Goodreads
Are you up for a thrilling adventure?
While camping in Wales, it doesn't take long for the Mystery Kids to stumble across a long-lost tunnel that leads to a valley full of secrets.
Follow the children as they are imprisoned in an old farmhouse, discover a hidden cave, sabotage a plane, rescue a missing man, undertake a perilous climb, and more!
This adventure novel is set in 1950's Britain and will suit anyone who enjoys Nancy Drew, the Hardy Boys or the Famous Five.
