• Air date: 26 Mar '17 6 episodes
      The fourth series sees AC-12 facing their most devious opponent yet! Under pressure from her superiors, DCI Roz Huntley charges a young man with a series of murders after months of fruitless investigation, but is he guilty? The Chief Forensic Investigator has doubts and turns to AC-12.
  • List of Episodes (6)
    • 1. In the Shadow of the Truth

      26 Mar '17
      DCI Roz Huntley is under intense pressure from her superiors to apprehend a serial murderer after months of fruitless investigation.
    • 2. Who Sows the Wind

      02 Apr '17
      AC-12 crank up their investigation into Operation Trapdoor. Kate makes progress in her undercover role.
    • 3. In the Trap

      09 Apr '17
      As AC-12 wrestle with the new forensic evidence casting doubt over Tim Ifield, Kate is approached by another woman claiming to have been assaulted by Michael Farmer.
    • 4. Moral Superiority

      16 Apr '17
      Roz's husband Nick is brought in for questioning by AC-12. But while Nick denies any involvement in Steve's attack, his suspicions about Roz mount.
    • 5. Lying Nest

      23 Apr '17
      DCI Roz Huntley struggles to allay her husband's suspicions. AC-12 find a new angle to pursue their case against her.
    • 6. Royal Hunting Ground

      30 Apr '17
      While Nick Huntley faces lengthy questioning, AC-12 remain convinced of Roz's involvement.