The Cold Case team is forced to enlist the help of a psychotic serial killer named Thomas Rice, AKA "the Gambler" (because he left playing cards at the scenes of his murders). The one woman who escaped death at his hands, the cool and poised Dr Clare Delaney, gets a dreadful reminder of her past ordeal and a fearful shock when a playing card is flung at her car windscreen as she sets off to make a house call on a wet, windy, dark night. The team look again at the Gambler's crimes, prompted by Boyd's unshakeable belief that Rice had claimed other, hitherto undiscovered victims.Boyd - who has personal links to the case - and Grace decide to use detective constable Amelia Silver to lure a confession from Rice.

Boyd and the team continue to begrudgingly rely on serial killer, Thomas Rice's assistance on the case, while also trying to protect Dr. Delaney from experiencing her terrifying ordeal once more at the hands of the copycat assailant. It becomes apparent that he might have help on the outside, so it's crucial that Boyd confronts one of Rice's intended victims, Dr Delaney, to find out what went on during her captivity. Why did he spare her life?

Boyd and the team take on the task of infiltrating the dark underworld of London's gangland crime families when Harry Newman makes a deathbed confession to 12 "unauthorised killings". Dr Grace Foley is intrigued by this strange expression but Boyd and the rest of the team are tempted to dismiss it as the meanderings of a dying man. Until, that is, forensic psychologist Frankie Wharton discovers that Newman did not die of natural causes, but has been murdered. They soon realise there's a lot more to Newman than they imagined. Added to all that, there's a link to a famous fifties trial in which a gangster was hanged for killing two policemen.

The postliminary inquiries into Harry Newman's past and the identities of the possible twelve murder victims uncover a connection to the infamous trial and execution of a well known gangster.

Boyd and his team struggle to find the truth behind the murder of a prominent Home Office adviser, when a petty criminal is acquitted of the crime. Once a prominent feminist activist, victim Katherine Reed had attacked the establishment at every opportunity, only to later switch sides. Boyd's progress on the case is hampered not only by a Home Office audit, which means the team will be shadowed throughout, but also by the fact that the original investigation was conducted by one of his old flames.

Whle facing a surprise audit from the Home Office, DCI Boyd (Trevor Eve) and the team try to continue their investigation into the murder ... but as they go on with their inquiries at Whitehall, they quickly discover the atmosphere to be very dark and secretive.

Twelve years after Joanna Gold famously disappeared in broad daylight on Hampstead Heath, the dress she was wearing is found in a lock-up. The team begin the hunt for her killer.

While under pressure to discover the truth behind the murder of young Joanna, DCI Boyd (Trevor Eve) slips up and makes possibly some irreversible mistakes. Joanna's killer begins stalking her sister.