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Unforgotten season 4: everything you need to know about the detective drama

Nicola Walker and Sanjeev Bhaskar star in Unforgotten Season 4.
Nicola Walker and Sanjeev Bhaskar star in Unforgotten Season 4. (Image credit: ITV)

Unforgotten season 4 sees Nicola Walker and Sanjeev Bhaskar return as London detectives DI Cassie Stuart and DS Sunil "Sunny" Khan to solve another cold case involving disappearance, long-held secrets — and murder. 

And series four follows a VERY cold case indeed, as Cassie and Sunny find themselves investigating the murder of a man who's been stored in a freezer!

Here's everything you need to know about Unforgotten Season 4.

More: See what's new on Netflix

Unforgotten Season 4 release date

Unforgotten season 4 starts in February on ITV at 9 pm in the UK. The fourth series will be shown in the US on PBS, but a release date is still to be confirmed. As you can see (below) there are plenty of options for catching up on past series of Unforgotten.

So what’s happening in Unforgotten season 4?

Nicola Walker and Sanjeev Bhaskar in Unforgotten.

Cassie and Sunny want justice for those who have been forgotten. (Image credit: ITV)

Following the trauma of the last case, Cassie made the decision to retire from the police force for her own sanity. But she faces an impossible dilemma when she learns she isn’t entitled to her full pension payment unless she completes her 30 years of service.

"The Dr. Finch case totally broke Cassie so, after almost 30 years in the police force, she’s decided she’s done with it," says actress Nicola Walker, who reprises her role as Cassie. "But then she gets the news that if she doesn’t complete exactly 30 years of service she won’t get her full pension. To have worked for that long and be just three months shy of getting your payout feels like a slap in the face to Cassie. But her dad’s getting rapidly worse with dementia, and she needs the money…"

As Cassie reluctantly goes back to work, she and DI Sunil "Sunny" Khan (Sanjeev Bhaskar) investigate after a dismembered body that had been stored in a freezer for 30 years is discovered in a London scrap metal yard.

The victim is identified as Matthew Walsh, a young man in his mid-20s who vanished in March 1990, and it’s believed the freezer was owned by Robert Fogerty, now deceased.

Cassie and Sunny soon make a breakthrough when they discover Robert committed a drink-driving offense on the same night Matthew went missing — and there were four others in the car with him.

Who stars in Unforgotten Season 4?

Nicola Walker as DCI Cassie Stuart

Will Cassie turn her back on the police force in Series 4? (Image credit: ITV)

Nicola Walker and Sanjeev Bhaskar return as detectives Cassie and Sunny and, as we know, Unforgotten always boasts a stellar ensemble cast playing the characters at the center of the new investigation. And this series is no exception. Ackley Bridge’s Liz White plays therapist Fiona Grayson, while Save Me’s Susan Lynch plays Liz Baildon, who’s juggling a high-flying career with the demands of a domineering mother (played by Sheila Hancock). 

Meanwhile, Andy Nyman plays businessman Dean Barton, who lives in Rochester with his wife Marnie (EastEnders’ Lucy Speed), their disabled son, Jack, and younger son, Casper. Finally, EastEnders’ Phaldut Sharma, plays Ram, an expectant father who’s always struggled to fit in.

"Essentially, it’s four mini-dramas within a whodunit and each of the suspect stories could be a series on their own," says Sanjeev Bhaskar, who returns as Sunny. "But even with so many great actors and great performances, I know viewers still focus on the relationship between Cassie and Sunny. They give the show its heart."

Is there a trailer for Unforgotten season 4?

What happened in previous seasons of Unforgotten?

In the first series, DCI Cassie Stuart (Nicola Walker) and DI Sunny Khan (Sanjeev Bhaskar) reopen a murder case from 39 years ago, when the bones of a young man are found in the cellar of a demolished house. Meanwhile, across the UK, four seemingly unconnected people are living very separate lives. In Leigh-on-Sea, Father Robert Greaves (Bernard Hill) is devoted to serving his parish while, in Cambridge, wheelchair-bound Eric Slater (Tom Courtenay) is a carer for his wife Claire, who has dementia. In Croydon, Lizzie Wilton (Ruth Sheen) helps disadvantaged kids while, in Westminster, entrepreneur Sir Philip "Frank" Cross (Trevor Eve) has just landed a top job in government. Do they know anything about what happened all those years ago?

In series two, Cassie and Sunny investigate when the perfectly preserved remains of a middle-aged man are found in a sealed suitcase in the silt of the River Lea in northeast London. As the drama plays out in the Cotswolds, East London, Salisbury and the South Downs, we meet four unconnected people who it seems are linked in some way to the victim. There’s Brighton-based lawyer Colin Osborne (Mark Bonnar), pediatric nurse Marion Kelsey (Rosie Cavaliero), school teacher Sara Mahmoud (Badria Timimi) and DI Tessa Nixon (Lorraine Ashbourne), the victim's wife, a respected police officer months away from retirement. What do they know about the incident? And how do they know each other?

The third series sees Cassie and Sunny investigating the death of Hayley Reid, a 16-year-old who vanished on New Year’s Eve 1999, the turn of the millennium after her remains are found on the central reservation of the UK’s M1 motorway. Meanwhile, across the UK, we meet four men who’ve been friends since school: local GP Dr. Tim Finch (Alex Jennings), TV presenter James Hollis (Kevin McNally), failing salesman Pete Carr (Neil Morrissey) and artist Chris Lowe (James Fleet). The investigation tests these long-held friendships to the limit and the ending of this series is particularly chilling.

Victoria Wilson
Feature Writer for What’s on TV, TV Times, TV & Satellite Week and WhatToWatch.com

With over 20 years’ experience writing about TV and film, Vicky currently writes features for What’s on TV, TV Times, TV & Satellite Week magazines plus news and watching guides for WhatToWatch.com, a job which involves chatting to a whole host of famous faces. Our Vicky LOVES light entertainment, with Strictly Come Dancing, Britain’s Got Talent and The Voice UK among her fave shows. Basically, if it’s got a shiny floor, she’s all over it! When she’s not watching TV, you might find Vicky in therapy… retail therapy that is!