When DCI Roz Huntley captures a serial killer, Forensic Coordinator Tim Ifield alerts AC-12 to a possible miscarriage of justice.

A dismembered body is discovered, and worries grow when Roz fails to report for duty. After further questioning of Michael Farmer unearths crucial new information, AC-12 challenge the case against him.

As shocking new evidence is unearthed, AC-12 step up their investigation into the case against Michael Farmer.

The discovery of new forensic anomalies appears to provide AC-12 with a major breakthrough. Meanwhile, Nick Huntley comes under scrutiny.

AC-12's future hangs in the balance after Hilton bars them from investigating Roz Huntley. But Roz's problems are building closer to home.

AC-12 pit their wits against Roz Huntley in a climactic duel to find Tim Ifield's murderer and unmask Balaclava Man.