The Experiences of Loveday Brooke, Lady Detective

What is a young lady like Loveday Brooke doing in a private detective agency? She's working there, as a clever sleuth, a female Sherlock Holmes of sorts. Excerpts:
"Loveday Brooke, at this period of her career, was a little over thirty years of age, and could be best described in a series of negations.
"She was not tall, she was not short; she was not dark, she was not fair; she was neither handsome nor ugly. Her features were altogether nondescript; her one noticeable trait was a habit she had, when absorbed in thought, of dropping her eyelids over her eyes till only a line of eyeball showed, and she appeared to be looking out at the world through a slit, instead of through a window. Her dress was invariably black, and was almost Quaker-like in its neat primness."