Nine-year-old Samuel lives alone in a once-great estate in Surrey with the family's housekeeper, Ruth. His father is dead and his mother has been abroad for months, purportedly tending to her late husband's faltering business. She left in a hurry one night while Samuel was sleeping and did not say goodbye. Beyond her sporadic postcards, Samuel hears nothing from his mother. He misses her dearly and maps her journey in an atlas he finds in her study. Samuel's life is otherwise regulated by Ruth, who runs the house with an iron fist. Only she and Samuel know how brutally she enforces order. As rumors in town begin to swirl, Samuel wonders whether something more sinister is afoot. Perhaps his mother did not leave but was murdered--by Ruth.