Liam returns to duty after the shooting and aids in the capture of crazed armed robber Sean Denning. However, Denning is released on bail so Liam and Garth have to return undercover as he searches for those who gave him up to the police. Garth, meanwhile, becomes increasingly concerned by Liam's fatalistic behaviour.
After Sophie's assault her phone and notes are missing leaving Liam and Garth at risk as they continue to try and gather new evidence against Denning. Their task is complicated by a malcontent ex-policeman working with the defence team trying to find undercover operatives.
Liam and Garth are called in by the Ministry of Defence to infiltrate a group of disgruntled former undercover soldiers planning a campaign of terror. Sent undercover in Liverpool, Garth takes the opportunity to reconnect with an old flame.
The base of the group Liam and Garth are infiltrating has been attacked by a group of ex-IRA men pursuing vengeance. The shoot-out tips Garth over the edge and he fleas. With one of the men being suspicious of Garth Liam has to find him.
Liam and Garth are sent undercover in a maximum security prison as the case against villain Vincent Hunter looks set to collapse. He is co-coordinating the targeting of witnesses and destruction of evidence from inside. Liam tries to gain his trust posing as a fellow prisoner whilst Garth operates as a prison officer trying to find out which officer is aiding Hunter.
Garth realises one DCI Davies's team is working with Hunter and forms a strategy to identify the culprit before they get to key witness undercover cop Debbie. Meanwhile, Liam is concerned when he learns Max is in trouble with the police after being targeted by bullies.
Government minister Jeremy Church is about to give a speech announcing the government's intention to legalise cannabis. The controversial policy has made Church a target and Liam and Garth are sent undercover at the conference venue to prevent a potential assassination. With a £1million price on the minister's head even his Special Branch bodyguards are potential suspects.
Garth has been released following the murder of Dominic and is furious with Liam following his failure to back him up. Meanwhile, Nicola tries to help boyfriend Josh when he is left £9,000 in debt to drug dealers after Garth stole his drugs and Liam gets closer to hotelier Gina.