Ridley's investigation into the body found in a hollow tree leads him to suspect different men in the victim's life. When another body is found murdered, with links to disgraced ex-copper Jean Dixon, the pressure builds to find the killer.

With Carol off the case, Ridley races to discover who shot Oliver in the hope of protecting Jack from becoming the team's prime suspect. But things take a turn for the worse when Ridley finds the murder weapon hidden in a shocking location.