Violet Hunter has been offered the role of governess at an estate in Hampshire but the employer insists that for the role she will be obliged to cut her hair short. Her perturbation at this causes her to seek Sherlock Holmes's advice.
Sherlock Holmes is contacted by Dr Trevelyan whose medical practice was set up and paid for by Mr Blessington who lives on the premises. Of late Mr Blessington has had spells of intense anxiety. Dr Trevelyan fears for his health and life.
What seems at first to be a harmless prank played upon a red-headed man is soon revealed to be much more: a sinister scheme devised by the Napoleon of Crime.