The Mephisto Club by Tess Gerritsen - USED

"Christmas Eve in Boston is no holy night for medical examiner Dr. Maura Isles. In a rundown house a woman has been dismembered in an act of carnage that leaves veteran cops in shock. Drawn on the wall, in blood, are ancient symbols, and a mirror-image word in Latin that, translated, says: "I have sinned." Then a second woman is found butchered on Beacon Hill, just outside the home of the leader of the Mephisto Club, a secret society dedicated to the study of evil, and to confronting it in its purest form. On the door have been scrawled yet more ancient symbols. Are they clues? Or threats? This is a form of evil Boston PD has never encountered before. And the only way Maura and detective Jane Rizzoli can defeat it is by turning to the people who understand the devil himself." - back cover.