The Adirondack Kids Book 6 Secret of the Skeleton Key. While preparing their pairate ship for the Anything That Floats Race, Justin and Nick discover an antique bottle riding the waves on Fourth Lake. Inside the bottle is a key that leads The Adirondack Kids to unlock an old camp mystery. Recommended ages 7-12. Pages:71. Size: 5.5′ x 8.5′.