🦃Maidens of the Cave by Lloyd Devereux Richards

Forensic anthropologist Christine Prusik has a knack for solving the most unusual cases—and for bending the rules in the process. When the bodies of young women start appearing in the caves of Indiana and Illinois, Christine immediately jumps into action. But her Chicago field office is undergoing a reorganization, and the boys’ club at the top seem more interested in getting all the paperwork in order than solving the murders. Christine isn’t going to let a little red tape stop her, and when she discovers that all the bodies have the same mysterious pin-sized bruise on the back of their necks, she realizes she’ll have to confront her own inner demons to find the killer.