The Serpent Pool (Lake District Mysteries, 4)

DCI Hannah Scarlett is determined to uncover the truth behind Emily Friend€s mysterious drowning in the Serpent Pool. But Hannah€s distracted by a new sergeant with a troublesome reputation, a new house, and new cause to doubt her partner--second hand bookseller Marc Amos. One of Marc€s best customers has been burned to death in the converted boathouse filled with priceless books. Then Hannah meets Louise Kind, sister of the historian Daniel Kind, who has just returned from America to work on a book about Thomas De Quincey and the history of murder. How are all of these elements related?