In Margaret Mounsdon's "Moon Hall Mystery," house-sitter Millie Midwinter is unexpectedly tasked with finding Becky, the missing sister of Charlie Pendennis, a hotel manager. Though initially hesitant, Millie is drawn into the search and uncovers more than she anticipated. As she digs through family secrets and Becky's correspondence with their reclusive great-aunt Polly, Millie navigates a web of complex relationships and hidden motives. Accompanied by Copper, the late Polly's spirited dog, Millie must solve the mystery amid the eerie and grand setting of Moon Hall, while dealing with her own personal upheavals.