Silent Death in Bloomington, MN

Two years ago, five women went missing. Last year, ten disappeared. Both times, it happened in December.
Now it's December again, and five more have vanished. To social worker, Madison Taylor, the women are not only her clients. They are her friends. Despite the recent discovery of the remains of five females, the police continue to be unhelpful because of the lifestyle the missing women lead.
Even after Madison is attacked and threatened, she stays determined to uncover the truth. How does her attacker know about the monster from her past? Madison's identity was never made public.
Is this the work of a serial killer or something more horrific?