Season 4, Episode 1:
Hell-bent on avenging his wife's death, Jack Halford is prepared to risk everything to kill the man responsible. As Detective Superintendent Sandra Pullman becomes aware of the dangerous situation Halford has put himself in, she has to act fast to prevent him confronting his nemesis, resulting in a crash that jeopardises the future of the entire team. With Gerry Standing, Brian Lane and Halford hospitalised, Pullman is forced to accept temporary help at UCOS from the super efficient DCI Karen Hardwick, a woman who irritates Pullman on every level. Threatened by a new face in the office and desperate to prove that they are still a crack team, even from a hospital bed, the boys need a case. So when their consultant Dr Finlay McKenzie mentions the suspicious death of a patient on their ward ten years ago, they take it on.
A motley crew of retired police officers re-opens troublesome cases that were never laid to rest.