The Silent Girl by Tess Gerritsen
In the murky shadows of an alley in Boston's Chinatown a hand has been discovered. On the rooftop above lies a woman's severed head. Two strands of silver hair - not human - cling to the body that lies nearby. These are Detective Jane Rizzoli's only clues, but they are enough for her and Dr Maura Isles to make a startling discovery: that this violent death had a chilling prequel. Seventeen years early a horrifying attack in a Boston restaurant left five people dead. Only one woman connected to the massacre is now still alive - a mysterious martial arts master who knows a secret she dare not tell. A secret that lives and breathes in the shadows of the city. A secret that may not even be human. It soon becomes clear than an ancient evil is stirring in Chinatown: an evil that has killed before, and will kill again - unless Jane and Maura can track it down, and defeat it.