Gates returns to rescue Arnott but leaves before Kate, her cover now blown, arrives to find evidence that a body had been stored at the warehouse. Arnott recalls that the chief torturer was called Tommy and admits to Kate that Gates saved him. She believes he is weakening in his attitude to Gates, whom he goes to see in secret, confirming his view that Gates is innocent of all the murders. Convinced that Gates is in danger but can bring the killers to justice Arnott persuades Hastings to let Gates set up a meeting with Tommy, recorded on a wire. Arnott and Kate intend to meet up with them but before they can do so Gates abducts Tommy to force a confession before committing an extreme act in the line of duty.

Danny's armed-response unit come under increasing scrutiny as AC-12 feed Kate information to help her crack their story. Steve makes a shocking discovery, then his own past catches up with him.

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.

When three police officers are shot dead during the hijack of a seized drugs transport, AC-12 move in to investigate possible police collusion.

Tensions rise in the OCG following the events at Eastfield. With troubling questions hanging over the identity of the mysterious H, suspicions mount among the AC-12 team.

As the hunt for H intensifies, Steve and Kate wonder if Hastings is guarding a dark secret.

AC-12 investigate DCI Jo Davidson's apparent mishandling of the murder of an investigative journalist.