Kelsey's dad has a new job and that means a new house?on the same property as a castle! Kelsey, Becca, and Leo can?t wait to explore, but what they find might lead to their most intricate case yet. How are an abandoned tree house, a wad of cash, a missing heirloom, and a mysterious creature roaming the grounds all connected? The Curious Cat Spy Club is determined to find out!