As DCI Butcher moves closer to charging the estranged husband of the family killed at the picnic, Jack and Nikki join DS Guillam in search of the truth. The team begin to realise they may have been looking down the wrong end of the telescope, and their lives are thrown into mortal danger. Soon enough, they are thrust into an unexpected and depraved world, and further murders are discovered. Jack and Nikki must fight to escape and bring those responsible to justice.
Meanwhile, Amy's dark past begins to catch up with her and she must decide whether to keep it buried or confront it head-on, risking her medical career and everything else in order to escape her demons. Amy's nightmare and the Lyell's investigation begin to converge. And when the crimes are linked to people in very high places, the team experience the difficulty of bringing the rich and powerful to justice.