Join the Dappledown Detectives for another adventure! On holiday, Libby finds herself bored of dog-sitting while her brother and his friends abandon her, so when a mystery presents itself to her, she can't resist but try to solve it on her own.
Learning about the legendary sea Captain and his missing boat, Libby is intrigued by the locals' interest in finding the vessel, but wary of their motives, she cannot help but think that there is more to the tale than a quest for lost treasure.
Help comes from an unusual source and Libby finds herself plunged into a world where mythical creatures could be real!
Will Libby be able to solve the mystery of the tunnel in the caves and find the boat before it is destroyed and lost of ever?