Book 3 of 21 in the bestselling standalone middle grade mystery series!
Collect All 21 Full Length Novels and 15 Short Stories
Over 15,000 reviews/ratings on Amazon

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.

Click "Buy Now" to read today! Free on Kindle Unlimited.

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