List of Trial & Retribution episodes

Five-year-old girl Julie Harris goes missing from home after being seen playing in the local playground. Suspicion immediately falls on Julie's mother's new boyfriend, Peter James (Lee Ross). But when her body is found inside a sewage pipe, evidence points towards local misfit Michael Dunn (Rhys Ifans). When items relating to the case are found in his flat, Walker has no doubt that Dunn is responsible for Julie's murder. However, when it is revealed that a frantic young officer who found Julie's body planted the evidence, Dunn's trial is thrown into jeopardy.

When young mother Susan Harrow fails to return home after a night out, her mother reports her missing to the police. Her body is later found on wasteground near to where she disappeared. A second victim, Marilyn Spark (Linda Henry), is attacked by the same assailant, however manages to survive and is taken to hospital for treatment. As a third victim is found murdered, Marilyn soon identifies the man responsible as Damon Morton (Iain Glen), and Walker must gather evidence to secure his conviction. When Morton's accomplice confesses to murder, Walker is suspicious.

Fifteen-year-old Cassie Booth goes missing whilst doing her local paper round, and her blood-stained clothes are later found in a nearby boathouse during a police search. Walker is suspicious when the owner of the boathouse, Karl Wilding, has a dodgy alibi for the time of Cassie's disappearance. Meanwhile, Pat is forced to deal with a persistent complainer, Stephen Warrington (Richard E. Grant), who has been hounding the station. Pat becomes concerned when Warrington starts stalking her, but soon realises that there is a link between Warrington and Walker's murder case.

Pat is asked to investigate a fifteen-year-old case in which Gary Meadows (Steven Hartley) was murdered by his boyfriend, James McCready (James Wilby), a case which was originally investigated by Mike. As the only witness to the murder was Meadows' young daughter, who was only seven-years-old at the time and unable to offer any kind of witness statement, Pat is forced to reinvestigate other lines of enquiry, while Mike finds himself trying to cover his own backside when evidence reveals that a psychic was used in an attempt to uncover evidence relating to the case.

Walker is assigned to investigate the discovery of a seventeen-year-old skeleton underneath the patio of a former bed and breakfast. Disillusioned with having to investigate such a case, he is especially angered by the fact that he has been paired with Pat's ex-boyfriend Jeff. When two further bodies and the skeleton of a premature baby are also found at the property, Kathleen Norton (Maggie McCarthy) is charged and sent to trial. However, Walker isn't entirely convinced that the alibi of former guest Graham Richards (Sean Chapman) is enough to keep in the clear.

Back on the murder squad, Pat is asked to investigate when a young-mother of two, Diane Leach, is abducted from a local wood. The confession of a local sex offender complicates matters, as Pat looks into the possibility that the father of a young protégé of the woman may be responsible for her disappearance. Meanwhile, Walker has worries of his own, as his ex-wife Lyn is dating an abusive, unstable man, Eric Fowler (Tim McInnerny), who turns into a manic-obsessive when she decides to leave him. Mike decides to take matters into his own hands, resulting in Fowler's death.

A severed female hand is found in the outreaches of Thames, which brings Róisín into contact with old friend Mike, who is now back in uniform after being found innocent at his murder trial. When a search fails to reveal the remainder of the body, a missing persons case which Mike has been personally asked to look at reveals the possible identity of the victim. When the au pair Carla Worth (Neve McIntosh) is found to have been posing as the dead victim to fool friends and neighbours, the victim's husband Greg (Charles Dance) is suspected of the victim's murder.

A young prostitute, Angela Dutton, plunges to her death from the eleventh floor balcony of a block of flats. The team discover that she was the daughter of a seventies TV star who was also found murdered twelve years earlier, wrapped in a blue eiderdown, although the killer was never found. Walker and Connor investigate seedy club owner Colin Thorpe (Colin Salmon), who was having a relationship with Dutton at the time of her death. A cover up involving a shady MP and the current DSI of the Vice Squad leads both Mike and Róisín into uncharted territory to find the killer.

David Harrington vanishes while on his honeymoon in London, leaving his wife Susan distraught and frantically searching for him. Her father contacts Walker, believing the police aren't taking the case seriously, but there's very little evidence to suggest foul play. However, Lisa's review into the CCTV surrounding his disappearance throws up a possible lead, in the form of a man with striking similarities to American serial killer Ted Bundy. Tom Franke (Michael Feast) is brought to trial, only to plead innocent by way of insanity. Can Walker prove Franke is not insane?