After Colin and Howie witness a gangland shooting and the culprits are not caught, the two familes are entered into the witness protection programme.
As part of the witness protection programme, the two families are relocated to a safe house in London. The compact nature causes tension to run high between the boys and Jackie uncovers a hidden secret from Colin's past.
The two marriages are in trouble as the couples continue to drift apart. Pauline contacts DS Tate to "pour her heart out". Meanwhile, the boys have a bad first day as garden landscapers.
After failing at being garden landscapers, Colin and Howie become traffic wardens. Pauline and Howie's marriage hits rock bottom as she gets closer to DS Tate and he moves into a dingy flat.
Colin and Howie try again at garden designing, with mixed results. Meanwhile the two, convinced Pauline is having an affair, stake out a hotel with disasterous consequences
In the explosive season finale, Colin and Howie's lives are put in risk when they come face to face with the killers.