England, 1961. Samuel's mother has been away for 113 days. 

Now it's just Samuel and Ruth, the housekeeper, alone in the once-great house. His mother is abroad, purportedly tending to her late husband's faltering business. Samuel yearns for her return but knows she must have had her reasons for leaving in the middle of the night, without saying good-bye. 

Although Samuel receives occasional postcards from his mother, her absence weighs heavily on his mind. And when his friend plants a seed of suspicion about strict Ruth, who rules the house with an iron fist, a dangerous idea is born. What if Ruth is responsible for his mother's disappearance?

Samuel is soon obsessed with finding answers. Is Ruth the one person in his life who truly cares for him? Or is she a killer with a murderous plan? And will Samuel be able to uncover the truth before it's too late?

Artful, haunting and deliciously claustrophobic, The Boy at the Keyhole is a story of truth and perception, and of the shocking acts that occur behind closed doors.