This is a Kate Shackleton mystery by Frances Brody. Kate is a private investigator at a time when ladies just didn't do that sort of thing; 1920's England. She is retained to find the daughter of Lady Coulton, the daughter conceived and born while Lord Coulton was abroad. The child was given to a trusted couple to raise as their own. In her search Kate has much to do at her local library, where rumors of a ghost are suddenly recirculating. In laying the ghost to rest the body of a strangled man buried under a load of books is found in the basement. An Italian organ grinder in poor health is also found (Kate has already come across his capuchin monkey, stowed away in her car). Umberto, the organ grinder, is too weak to have committed the murder, but is charged for it by the local police. Kate sets out to find the actual murderer, at some danger to herself. An interesting read. This is actually the sixth in a series, though it works quite well as a standalone.