The crew of NEW TRICKS unequivocally bids farewell in the twelfth and final season of the light-hearted crime series about the lives and work of the Unsolved and Open Case (UCOS) squad utilizing the expertise of a retired police officers when new evidence turns up. For the bulk of the series, the squad was made up of recovering alcoholic Brian Lane (Alun Armstrong, GET CARTER), haunted Jack Halford (James Bolam, THE LONELINESS OF A LONG DISTANCE RUNNER), and "last man standing" Gerry Standing (Dennis Waterman, SEXY BEAST) whose career trajectory took a nosedive after she shot a dog during a hostage rescue. Replacing Halford after his death is cocky Steve McAndrew (Denis Lawson, DEAD HEAD) in season nine, followed by intellectual Dan Griffin (Nicholas Lyndhurst, ONLY FOOLS AND HORSES…) replacing Lane in season ten, and then DCI Sasha Miller (EASTENDERS' Tamzin Outhwaite) taking charge in season ten as her first command posting. Politically-savvy Deputy Assistant Commissioner Strickland (Anthony Calf, THE MADNESS OF KING GEORGE) allows the team plenty of wiggle room even when investigating sensitive cases, but will come down on them when they blatantly break the rules. The team's personal lives also interfere with and inform their investigations. Miller is constantly cleaning up for her troubled teenage son (Harry Lister Smith, PAN) while trying to have a love life. Standing is starting to realize just how much of his family life he is missing out on with the birth of his new grandson to his single daughter (Amy Nuttall, DOWNTON ABBEY). Cash poor McAndrew is finding that he can no longer live paycheck to paycheck when the bills pile up and he has promised estranged eighteen year old son a new car. Griffin, who mentally-ill wife is hospitalized in long term care, is conflicted over moving forward in his relationship with forensic anthropologist Fiona (Tracy Ann Oberman, FILTH) when she gets a prestigious job offer in Scotland. The team's newest, temporary member, Ted Case (Larry Lamb, PLACE VENDŌME) would like to extend his stay in lieu of a caravan trip across Europe with partner Pat (Peter Vollebregt, THE ROYALS).

Standing gets a fitting sendoff in the two-part opener "Last Man Standing" when remains buried beneath a house turn out to be those of the missing DCI Martin Ackroyd (Michael Shaeffer) who first recruited him onto the gang taskforce in 1983. As he re-opens the case and starts investigating Bryant (Nigel Cooke) and McCabe (Nigel Betts), two members of the squad believed to have been in the pocket of the Chapman crime family, Standing finds himself the prime suspect. As his own past associations with gangsters are revealed and damning evidence has his own squad questioning whether Standing is being framed or if they ever really knew him at all. Ted Case, who provided some crucial assistance on Standing's case, replaces him and Miller (still recovering from a drive-by shooting in the previous episode) in "The Curate's Egg" as the team re-open the murder of a white preacher who had received a series of racist letters because of his black wife (Adjoa Andoh, LAW & ORDER: UK) and children (Lloyd Everitt, AGATHA CHRISTIE'S PARTNERS IN CRIME's Camilla Beeput, and Percelle Ascott) when the youngest come forth with repressed memories. The team initially focuses on the author of the letters but Case starts to believe that the motive for murder may be something more complex than racism as familial dysfunctions and the vicar's questionable relationship with a female curate come to light. In "The Wolf of Wallbrook", the blow-up of a fashion photograph from the eighties against the backdrop of London Bridge reveals that it has not only captured mid-fall the death of futures trader Charlie Hayes but also that the apparent suicide may actually have been a murder. The investigation of the Thatcherite "Wolf Pack" of traders exposes more than the usual excesses including more motives for murder than mere money.

When the findings of a recently deceased pathologist are discredited, Strickland brings the team in to reinvestigate the apparent overdose and drowning of cricket player AJ Da Silva which his highly-placed father (Amerjit Deu, BEND IT LIKE BECKHAM) believes was actually a murder in "Prodigal Sons". While AJ may have been the apple of his father's eye, the team soon discover that his teammates – among them, his younger brother (Prasanna Puwanarajah, MÖBIUS – had many reasons to hate him including an affair with the wife (Ella Kenion) of a fellow player who then committed suicide. Steve gets starstruck in "The Fame Game" when messages on a recently recovered mobile phone cast suspicion on the apparent suicides of married celebrity lookalikes Jim and Anna Briggs. While Anna was having an affair with an unknown party was apparently planning to run away on the day of her death, Jim was revealed to have been stalking his celebrity double Mikey Bishop (Michael Higgs, EASTENDERS) whose micromanaging wife (Eva Pope, CORONATION STREET) seems to be hiding as much as Anna's sister (Lucy Benjamin, DETECTORISTS) and John's Bruce Willis-double best friend (Tim Chipping, TROY). In "The Russian Cousin", the coded notebook of a murdered private detective turns up in the police mail, leading the team to his last clients: pastry chef Alison (Nadine Marshall, SECOND COMING) who hired the dead man to track down the abusive boyfriend who stole £30,000 from her, and Barry (Dean Andrews, LAST TANGO IN HALIFAX), a builder dying of cancer who was also the victim of a robbery which included "rainy day money" in the form of a rare stamp valued at £40,000.

"The Lottery Curse" strikes when the dismembered remains of a missing lottery winner have reporters once again hounding her drug-addicted husband (Jack Deam, SHAMELESS); but the team finds more compelling leads in the motives and alibis of the fellow winners that comprised "The Dream Team", an animal rescuer (Amanda Root, PERSUASION) and gardening supply store owner (Derek Riddell, STRATHBLAIR) and his bitter wife (Adie Allen, CASUALTY), as well as the young builder (Henry Garrett, THE WICKER TREE) hired to build the swimming pool where the body was unearthed. When a sinkhole opens up in a cemetery, the marble bust used to murder herbalist guru Jason Henway is discovered beneath the coffin of one of his clients. The woman's daughter (Denise Gough, ROBIN HOOD), who had blogged against the victim's company after he convinced her mother to discontinue cancer treatment in favor of alternative medicine, becomes the prime suspect; however, the team also become suspicious of the victim's partner (Ramon Tikaram, KAMA SUTRA: A TALE OF LOVE) and the profiteering cryogenics business of his brother (David Haig, PENNY DREADFUL). When the team is suspended as a result of the fallout from the Henway case midway through their investigation into the 1999 New Years' murder of mental health campaigner Greg Collins, the team decides to go out with a bang and continue to the investigation which implicates a politician (Meera Syal, BROADCHURCH). Miller and Strickland suspect that Assistant Commissioner Cynthia Kline (Geraldine Somerville, HARRY POTTER AND THE ORDER OF THE PHOENIX) may have her own political motivations for disbanding UCOS.