Unforgotten

The new series starts with the discovery of body found in a sealed suitcase in the silt of the River Lea. With the body preserved but clearly having been there a number of years, DCI Cassie Stuart and DI Sunny Khan begin the complicated task of identifying the victim and investigating his murder.

With an expensive watch found on the body the only evidence to go on, the item is sent to forensics who suggest approaching a watchmaker who may have repaired it to find out more about its owner.

Meanwhile, we meet four seemingly un-connected suspects who may have a link to the victim – DI Tessa Nixon who is struggling with her loner son, nurse Marion Kelsey who works with chronically ill children, Brighton-based barrister Colin Osborne who is in the process of adopting a little girl with his husband, and teacher Sara Mahmoud who is interviewing for a new position in a school that needs turning around. How do any of them link to the victim, though, and why would one of them kill him?

Detectives Cassie and Sunny begin to find out a bit more about who David Walker was through speaking to his ex-wife Tessa.

Further examination of David Walker's history suggests that he was a troubled man with a number of issues. Marion has a prickly chat with Cassie about her past and the investigation reveals her close relationship with an IRA activist. As the police enquiries encroach on their lives, Sara and Colin open up to their partners.

A disturbing allegation about David opens up a second line of enquiry for the team. How much Tessa actually knew about David's life threatens to ruin her relationship with her husband and son. Marion gets into trouble at work and jeopardises her marriage by refusing to open up about her past. After having his phone stolen and information exposed, Colin is blackmailed again - and Sarah's secrets push her family to breaking point.

In the penultimate episode of the series, Cassie turns her attention to investigating the goings-on at the Brentford house and the theory that one or more of the suspects may have been abused at the gatherings that took place there.

With each of the suspects having a motive, opportunity or connection to victim, David Walker, Cassie and Sunny try to join the dots to discover who actually killed him 25 years earlier.