A young orphan woman, Violet Hunter, comes to Holmes for advice on whether to accept a strange, but well-paying position in the countryside. She is a governess and her potential employers, a well-off landowner and his second wife, want her to take care of their young son, but also to fulfill strange requests, such as cutting off her beautiful hair, wearing a specific dress, and sitting by the window for long periods.

Holmes suspects something is amiss but does not believe there to be an immediate danger. The young woman accepts the job as she is destitute and after a few weeks telegraphs Holmes to come and help her. While living in the manor, called the Copper Beeches, she has discovered that someone is being kept locked in one of the wings. The detective concludes that it is the family’s older daughter, who has the right to a large part of the estate. She was engaged to marry a local man, but her father did not want to lose the money, so he and his second wife locked her up after an illness. Violet resembles her and was hired to fool the fiancé into thinking that the daughter no longer wants to marry him.