Natural Killer?

A brutal murder, a callous killer and a wall of silence. DI Rose's new case contains all the elements of a classic homicide. Except:
The victim is an elderly lady.
The pathologist has branded mode of death 'unusual.'
There is no forensic evidence.
Frustrated by the lack of any real leads, Rose finds herself drawn to a box of files in the victim's home. Are its subjects somehow connected to the old lady's death? If so, what secrets could be terrible enough to justify such a violent murder?
Before Rose's questions can be answered, a second dead body is discovered. She finds herself under pressure to solve the case. But her list of suspects is only getting longer: and whilst she is certain that the killer lurks among them, they all seem intent on misleading her. How can she determine who's guilty, when she is struggling to tell the truth from the lies?
As the investigation progresses, Rose begins to suspect a conspiracy. For as one dead-end evaporates, another appears. A scary picture is unravelling: one infinitely darker than she'd imagined. Can she assemble the puzzle pieces and identify the killer? As she finally gets close to the truth, Rose is forced to put herself in the firing line.