Following the violent attack she suffered in prison, Lindsay is granted special dispensation to visit her dying mother. Meanwhile, deputy chief constable Dryden shrugs off allegations about his relationship with Lindsay and possible links to the ambush.

Lindsay fights for her life as troubling details emerge of a vicious conspiracy involving corrupt police officers. With growing evidence of links between DCC Dryden and the ambush, Hastings is under pressure to arrest his senior officer.

AC12's investigation finally exposes a vicious criminal gang run from within the police. But while Steve now appears convinced of Lindsay's innocence, Kate remains determined to prove she had a role in the ambush.

DCI Jo Davidson receives new information about the whereabouts of a suspect in the unsolved murder of investigative journalist Gail Vella. En route to raid the property, she spots an armed robbery in progress and stops the convoy. Suspicious of her motives, AC-12 launch an investigation. Still dealing with the fallout from their explosive investigation into undercover officer John Corbett, AC-12 soon realise they are facing their most enigmatic adversary yet.

Having opened an official inquiry into DCI Jo Davidson and Operation Lighthouse, AC-12 begin to suspect a cover up. Steve and Chloe dig into Gail Vella’s controversial reporting for clues to her murder, and find links to previous AC-12 cases. Their investigation takes a shocking turn when they begin to scrutinise Jo's personal life.