BETRAYAL OF TRUST

This ninth installment of Cooper’s thriller series follows a sleuthing couple trying to unmask a knife-wielding killer.

Dr. Brad Parker, director of the Maine Translational Research Institute, is supposed to meet an “expert in running clinical trials” for breakfast. But cops discover this expert, Dr. Eric Salton, dead from a brutal stabbing in his hotel room after receiving an award at a Boston cancer research conference. Brad and his fiancée, Lt. Karen Richmond, who heads a major crimes unit, get details from a friend and local homicide detective. It turns out Salton was known for sexually harassing women and had the power to ruin careers (“Salton made a practice of hitting on women who worked for him and had no hesitation in using his power over them”). This produces quite a few suspects; the police, per security footage, know the murderer is female. Then a second victim is killed in the same fashion, another doctor Brad had known. Was this man guilty of the same transgressions as Salton? Or is there another motive that Brad and Karen have yet to connect to anyone? In either case, the killer is far from finished. Cooper’s slow-burn mystery is at its best in chapters conveyed from the killer’s perspective, which give readers only a bit more insight than the sleuths possess. This use of POV reveals a frighteningly methodical culprit who grows increasingly blood-chilling (“she drove home, stopping at a dumpster along the way to dispose of. But she kept her knife. She wasn’t finished yet”). Though Brad dreams up a clever scheme to identify the killer, the story culminates in a largely predictable final act. Still, the recurring leads are immensely likable, especially when they’re deciphering clues together (“Karen gave me a half-smile. ‘Not bad, we’ll make a detective out of you yet’”).

This leisurely but absorbing murder mystery boasts indelible detectives and a particularly nasty villain.