Unforgotten

DCI Cassie Stuart and DS Sunny Khan investigate when a skeleton is found beneath a demolished house. The discovery of a car keys lead the pair on a trail to identify who the victim is, and they find a diary of a young man missing since 1976.

After identifying the body in the cellar as Jimmy Sullivan, the hunt for his murderer begins. Cassie and Sunny begin the investigation by following up on the names written in Jimmy’s diary. In Liverpool, Cassie meets Jimmy’s mother, who is relieved at the prospect of finally finding out what happened to her son after he went missing. The name ‘Frankie C’ is identified as Sir Phillip Cross – a newly government-appointed entrepreneurial czar, who denies that he ever met Jimmy.

Cassie and Sunny visit a priest who remembers Jimmy fondly, but unfortunately Father Robert Greaves is unable to identify ‘Jo-Jo’, the mysterious person who gave Jimmy the diary. The investigation also leads to another person who remembers Jimmy well, Eric Slater, who used to be a bookkeeper at Arlingham house.

The investigation into Jimmy’s death continues, with the discovery of marks on his body consistent with known gangland torture methods. Cassie and Sunny question Sir Phillip to find out exactly what his involvement was with a prominent East End crime family and Eric and Claire's anniversary party gets underway.

Sir Phillip Cross makes a difficult decision in order to protect his family and salvage what is left of his reputation. Ray returns home to find Lizzie gone and a note that reads ‘I’m sorry’ and Father Robert comes clean to his family and the police.

Father Robert’s revelations have lasting repercussions. Things are especially difficult when Caroline goes into premature labor. Bella and Josh deliberate over how best to deal with their father and the search for Lizzie continues. Maureen is finally able to lay Jimmy to rest.

Detectives Cassie and Sunny, who find themselves thrown into another historic murder case with the discover of a body. This time it's the perfectly preserved remains of a middle-aged man found in a suitcase in the silt of a London river. As the detectives begin the complicated task of trying to identify the victim, four unconnected people go about their business - Brighton-based lawyer Colin Osborne, paediatric nurse Marion Kelsey, teacher Sara Mahmoud and respected police officer Tessa Nixon - unaware they are about to be dragged into the investigation.

With their victim identified, Cassie and Sunny begin to find out a bit more about David Walker by talking to his ex-wife, DI Tessa Nixon, who reveals he suffered from depression. A search through the original investigation files and some numbers from David's pager help build a picture of him - and also lead to a few potential suspects. However, his son Jason struggles to deal with the news that someone murdered his dad.

Sunny makes further investigations into David Walker's life that suggest he was a troubled man with a number of issues. Marion has a prickly chat with Cassie about her past and the inquiry reveals her close relationship with an IRA activist. As the police investigation encroaches on their life, Sara and Colin open up to their partners with secrets about their past.

Marion jeopardises her marriage by refusing to open up about the past to her husband, Colin is blackmailed even further and the secrets of Sara's past push her family to breaking point. A disturbing allegation about David opens up a second line of inquiry, and when Tessa is called in for questioning again it threatens to ruin her relationships with her husband and son.

Cassie turns her attention to Brentford house and the theory that one or more of the suspects may have been abused at the gatherings there. Marion is questioned again after Sinead's allegation that David could have been an IRA target. The detectives also look further into the accusations made against Colin while he was working in the city - but something does not quite seem to add up. Was his alleged victim telling the truth - and if not, why would she lie?

With the suspects in the murder of David Walker all having either a motive, opportunity or connection to the victim, Cassie and Sunny are left with a massive puzzle to solve. Cassie soon focuses in on Sara, whose alibi seems too perfect, as if it has been put together by an accomplice of the ex-prostitute - and the team is soon investigating the possibility of a wider revenge plan. Meanwhile, interviews with Colin and Marion's loved ones prove revealing.

When human remains are found buried in the central reservation of the M1. Cassie and Sunny begin the task of identifying them.

The search for what happened to Hayley begins as the team travel down to Middenham to meet her family.

Cassie and Sunny begin interviewing the four male occupants of The Spinney over the millennium, who all have fairly consistent accounts of the time spent in Middenham. The rest of the Bishop Street Station team look at the timelines and leads from the original investigation.

Cassie and Sunny suspect that the men all colluded in lying about their version of events for that evening, but why? The press begin to circle as they find out that James has been questioned in connection to the Hayley Reid case.

Cassie and Sunny finally get closer to some truth about the night Hayley disappeared and the case takes a devastating turn for Cassie.

Under the glare of media spotlights, the team race to find the evidence to prove the identity of Hayley's killer.

Dr Peter Dean, forensic advisor, talks us through the discovery and recovery of skeletal remains and how Unforgotten makes this as authentic as possible.

The cast and crew of Unforgotten provide an introduction to the universal themes of relationships and betrayal in this murder mystery series.

A look at how this series has progressed from Series 1.

The cast discuss the impact of living a lie.

The cast look at the relationship between the characters in this series.

A look at the set design within the show.

Sam Ives, Art Finisher, explains how the props were created.

A look behind the flashback scenes which provider the viewer with clues.

Sunny reveals the contents of his rucksack!

DCI Cassie Stuart and DI Sunil 'Sunny' Khan reunite to solve another historical crime, their first since they chose to walk away from a case in which victims of child sex abuse had worked together to murder their abusers. This new investigation sees four men under scrutiny when the body of a teenage girl is found at a building site off the M1 motorway. It's revealed that she's been missing since the turn of the millennium and it's up to Cassie and Sunny to figure out whether any of the men had anything to do with her death.

The writer, director and cast discuss the background to the programme.

Detailed insight into the filming of this series' opening scene.

A look at some of the locations features in the series.

How integral social media is to our lives.

The actors playing the key suspects in the series discuss their characters.