Travel to the misty hills of Scotland for a hauntingly good rescue mission inside a towering ancient castle. When the Thea Sisters learn that their good friend Bridget has to rush home for a sudden family emergency, they immediately offer to help. But shortly after arriving in Scotland, the situation takes a scary turn when Bridget completely disappears. The five friends know they must find her before it is too late. Their search leads them deep into her family's giant, crumbling castle, where they uncover a trail of cryptic messages, old Celtic legends, and rumors of hidden treasure. They have to navigate dark hallways, solve ancient riddles, and figure out who would want to kidnap their friend. It is a true test of their bravery and friendship as they work to uncover the castle's biggest secret.