The team investigate the murder of an East German immigrant, but they only have his mysterious final words to work with. As they attempt to piece together his remarkable story, Sandra attempts to gain the trust of his estranged daughter.

The episode was rated 8.00 from 54 votes.

When the gun used to murder a talented young boxer 11 years ago surfaces in an armed robbery, UCOS are drawn into the darker side of professional boxing in a case that causes conflict and friction among the team.

The episode was rated 8.00 from 46 votes.

When 18-year-old debutante Barbara Linden-Warner disappeared without trace 27 years ago, the assumption at the time was that she had been kidnapped and her father, a wealthy British arms manufacturer, paid a ransom for her return. When new evidence emerges about her last movements, the indication is that she may still be alive.

The episode was rated 8.00 from 46 votes.

Brian Lane knows his days at UCOS are numbered. Meanwhile the team investigate a 16-year-old murder of a young mum by her criminal husband that could be a miscarriage of justice. However Gerry Standing feels very strongly that the conviction should not be called into question.

The episode was rated 8.02 from 62 votes.

When the team investigate the death of an MP's researcher and find themselves in hot pursuit of a mysterious Bosnian woman, Strickland introduces Pullman to a war crimes prosecutor who proves to be more than helpful to their case.

The episode was rated 8.04 from 45 votes.

As Lane comes to terms with life after UCOS, Esther asks him to help one of her book club friends find her missing brother - but will his nose for the truth get him into further trouble? And how will his former colleagues cope without their most dogged sleuth?

The episode was rated 8.05 from 55 votes.

A woman is sent anonymous emails from someone claiming to know what happened to her husband Phillip Mackenna, a prominent scientist working on cold fusion who disappeared while on a train to Paris. As the team investigate, DAC Strickland receives a warning from Whitehall.

The episode was rated 8.09 from 57 votes.

The team reopen the case of zookeeper Zac Halsey, originally thought to have been mauled to death by a tiger, when blood evidence discovered in his lodgings suggests he was killed before he was found in the tiger's enclosure.

The episode was rated 8.09 from 43 votes.

As the detective drama returns, Gerry is spooked by the discovery of UCOS's latest victim - a cop, whose body has lain untouched under a basement for 30 years. As accusations of police corruption and underhand dealings begin to surface, Gerry has to face up to some skeletons in his own closet and it's a race against time for the team to help before his murky past catches up with him. While babysitting his grandson, Gerry becomes convinced that only he holds the key to the investigation and goes Awol to uncover the truth.

The episode was rated 8.10 from 80 votes.

Thirty years ago, Strickland and a group of his associates, including Stephen Fisher, were involved in a covert operation on behalf of MI5. Now, someone is trying to kill all the members of that group and Strickland turns to the UCOS team for help.

The episode was rated 8.10 from 48 votes.

Jack announces that he he has decided to leave the team, but before Sandra, Brian and Gerry can question his reasons, Whitehall figure Stephen Fisher shows up with one of his secret cases featuring the unsolved murder of a woman dating back around a hundred years. With only 24 hours to solve it, the team attempt to find time to get to the bottom of Jack's surprising decision and attempt to persuade him not to leave.

The episode was rated 8.11 from 72 votes.

After being released from jail, notorious paedophile John Davies admits to the abduction and murder of a child 25 years previously. Suspicious of his motives, the detectives reopen the unsolved case in an unusual attempt to prove his innocence, reinvestigating the boy's disappearance while on a demonstration with his left-wing activist parents. Guest starring Adrian Schiller (Being Human) and Samantha Bond (Outnumbered)

The episode was rated 8.15 from 41 votes.

Danny takes Gerry on the run as they search for the proof they need to prove his innocence - despite Gerry remaining tight-lipped about his involvement with dodgy dealings in his old unit. The stakes are high as the Unsolved Crime and Open Case Squad goes after one of the biggest crime families in London, and it's those closest to Gerry who are dangerously put in the firing line.

The episode was rated 8.16 from 75 votes.

As part of his initiation into a motorbike gang called The Braves, Reece Chapman plans to murder the rival gang member he believes killed his father Eddie, the former leader of The Braves. Desperate to stop Reece, his girlfriend Stephanie Parr turns to UCOS for help in solving Eddie's murder to prove he's targeting the wrong man.

The episode was rated 8.17 from 53 votes.

Pullman seizes the chance to solve a murder that she believes is linked to her first ever case, and the team start putting together a jigsaw puzzle of suspects from a photograph taken in a London park in the 90s. Eventually faced with increasing pressure to hand over the investigation, Sandra makes a huge decision, which is going to change UCOS forever.

The episode was rated 8.24 from 51 votes.