Investigating the murder of a teenage boy, Nikki and her team are forced to question police methods. Although Thomas discovers evidence that throws the time of death into doubt, DCI Claire Ashby seems more concerned with building the case against her main suspect. With pressure building on the police to secure a conviction, the Lyell team must fight to ensure that inconvenient truths aren't overlooked. Meanwhile, Clarissa notes a troubling parallel with a case from the start of her career. Is the real murderer still out there?