Murphy's Law

DS Tommy Murphy finds himself before a disciplinary review board after having shot a suspect during an arrest and soon out of the force completely. He approaches a psychologist, Mark Maddison, who runs a support group for individuals who have lost someone to a violent crime but where the perpetrator is known but has never been convicted of the crime. In fact, Murphy is undercover as at least three murder suspects have been killed and all had some connection to a member of Maddison's group.