The Lodger - Marie Belloc LOWNDES

"The story is about a Jack the Ripper-type murderer known only as "The Avenger" in London, who has been killing young blonde women. Meanwhile, a mysterious man arrives at the house of Mr. and Mrs. Bunting looking for a room to rent. The Bunting's daughter, Daisy — a blonde model — becomes enamored with the lodger. At the same time, Joe — Daisy’s boyfriend and a detective assigned to The Avenger case — becomes jealous of the lodger and suspects he may be the murderer." (From Wikipedia)