1978. Mrs. Medlock is the dutiful housekeeper at Marwood Manor. Though the glamour has faded from the estate and she is one of the few staff that remains, Mrs. Medlock continues to serve the Lord and Lady, and care for their sickly young son. For over the past twenty years, Mrs. Medlock has become the keeper of secrets. Secrets of the family. Secrets of her own. Secrets that may be found in the manor's walled garden, out of sight but not forgotten. When a distant relative, Mary, arrives at the property in need of a place to live and with a determination to explore, Mrs. Medlock fears the secrets of Marwood are no longer safe. And digging up the past may have deadly consequences for them all . . .