A Killer's Mercy

Is it ever justified to kill a murderer? In the middle of nowhere, three men are shot to death. Each man had received a piece of paper, telling them to meet at the very spot they were killed. FBI agent Jo Pullinger is tasked to find the person behind the cold-blooded shootings. As she digs further, she discovers the dead men had been previously charged for crimes that they were never punished for. Someone is enacting their own form of justice. Can Jo stop them before there are more dead bodies?