ITV drama Unforgotten has returned for a fourth season, with a brand-new cold murder case for the team to solve.
Nicola Walker and Sanjeev Bhaskar lead the cast, once again reprising their roles as cold case cops DCI Cassie Stewart and DI Sunny Khan.
As with previous seasons, the line-up of potential Unforgotten suspects is typically star-studded, with the likes of Dame Sheila Hancock and Life on Mars star Liz White joining the cast for season four.
Season four begins with the discovery of a body dumped at a London scrapyard, and our detectives learn that the remains (which had been hidden, frozen, inside a freezer) belong to an individual who's been missing since the 1990s.
Read on for our guide to the cast and characters of Unforgotten seasons one through to four.
Unforgotten season four
Nicola Walker plays DCI Cassie Stewart
Who is DCI Cassie Stewart? Forget maverick cops - lead character Cassie Stewart is a professional, level-headed murder detective devoted to solving cold cases and bringing the killers to justice for the victims' families. A widow, she has two grown-up sons. She also has an excellent working relationship with her sidekick Sunny.
However, season four kicks off with a rocky start for Cassie: following a nervous breakdown, she unsuccessfully requests to retire three months early from the police force, just shy of her 30 year anniversary.
Where have I seen Nicola Walker before? You may have recently watched Nicola Walker play Jane Oliver in Collateral, or Hannah Sterne in The Split, or Gillian in Last Tango in Halifax, or perhaps you remember her as Ruth Evershed in Spooks? Other credits have included River, Babylon, Inside Men, and Torn.
Sanjeev Bhaskar plays DI Sunny Khan
Who is DI Sunny Khan? Sunny is Cassie's second-in-command. He is also dedicated to his job, working hard to solve long-ago murders with empathy and intelligence – despite being an overworked single father of two exasperating teenage girls.
At the beginning of season four, Sunny is under even more pressure - with Cassie absent, it's him who initially takes the lead in the new cold case investigation. (Hopefully Sunny's famous backpack will spur him on.)
Where have I seen Sanjeev Bhaskar before? Sanjeev Bhaskar is best known for his comedy work, starring in sitcom The Kumars at No 42 and appearing in the BBC sketch comedy series Goodness Gracious Me. You may have spotted him in Paddington 2 (as Dr Jafri) and The Indian Doctor (as Dr Prem Sharma), and in the Beatles film Yesterday (as Jed Malik). He is set to play the role Cain in the upcoming Neil Gaiman adaptation The Sandman.
The actor has led the cast of Unforgotten alongside Nicola Walker since day one.
Peter Egan plays Martin Hughes
Who is Martin Hughes? Cassie's dad, whom she previously lived with. He is a widower but is now in a long-term relationship with a new woman, a previous point of tension between him and Cassie. In season four he also has early onset dementia, which results in him developing depression and alienating Cassie.
Where have I seen Peter Egan before? A veteran actor, his credits include Hold the Sunset, Downton Abbey (as Hugh "Shrimpie" MacClare), Home Again, Big Breadwinner Hog, Prince Regent, and Ever Decreasing Circles. He's recently starred in Netflix's After Life season two, alongside Ricky Gervais.
Alastair MacKenzie plays DCI John Bentley
Who is DCI John Bentley? An officer on the original case in season three. He helped with the new investigation and developed an interest in Cassie, before later establishing a relationship with her. At the start of season four, it looks like the pair are fully committed.
Where have I seen Alastair MacKenzie before? The actor recently played Guy Riverty in Deep Water, and Jamie in the Cold Feet reboot, and Craig Petrie in ITV's The Loch. He appeared as William Brereton in Tudor drama Wolf Hall, and played Lord Rothcroft in Dracula, but is perhaps best known for starring as young laird Archie MacDonald in Monarch of the Glen.
Jassa Ahluwalia plays Adam
Who is Adam? Cassie's son, who has yet to find a job.
Where have I seen Jassa Ahluwalia before? Known for his role on Unforgotten, he also played Dimitri in Peaky Blinders, and Rocky in Some Girls. Other past projects include Ripper Street (as Vincent Featherwell), and the film The Whale.
Liz White plays Fiona Grayson
Who is Fiona Grayson? A therapist who lives in the Peak District with her husband and two children.
Where have I seen Liz White before? She's best known for playing Annie Cartwright in the BBC time-slip series Life on Mars, and as Emma Keane in the Channel 4 drama series Ackley Bridge.
Susan Lynch plays Elizabeth Baildon
Who is Elizabeth Baildon? A high-flying career woman who lives in Cambridge.
Where have I seen Susan Lynch before? She has starred in the likes of National Treasure, Sex Education, Doctor Who, Apple Tree Yard, the Downton Abbey film, and 16 Years of Alcohol.
Sheila Hancock plays Eileen
Who is Eileen? Elizabeth's cantankerous and bed-bound mother.
Where have I seen Dame Sheila Hancock before? The acting legend is known for a long career on the stage on both sides of the Atlantic, but she's also starred in recent projects like Endeavour, A Discovery of Witches, The Boy in the Striped Pyjamas, and Delcious.
Andy Nyman plays Dean Barton
Who is Dean Barton? A seemingly legitimate businessman, he's happily married with a disabled adult son.
Phaldut Sharma plays Ram Sidhu
Who is Ram Sidhu? An expectant father in Southall.
Where have I seen Phaldut Sharma before? Recent roles have included The Singapore Grip, Avenue 5, The Accident, The Personal History of David Copperfield, Hanna, and EastEnders (as AJ).
Clare Calbraith plays Anna
Who is Anna? Ram's pregnant wife.
Where have I seen Clare Calbraith before? She played Jane Moorsum in Downton Abbey, and Clare in Baptiste. She's also starred in Vera (as Shep), The Innocents, Anne, Mindscape, Home Fires (as Steph Farrow), and The Shadow Line.
Lewis Reeves plays DC Jake Collier
Who is DC Jake Collier? A member of Cassie and Sunny's team.
Where have I seen Lewis Reeves before? The actor has appeared in Unforgotten since series one. He played Jake in the Netflix drama Crazyhead, and is the voice of Gareth Walker in FIFA 17 and FIFA 18. International viewers will also recognise Reeves as David in Michaela Coel's acclaimed BBC series I May Destroy You.
Unforgotten season 3
Alex Jennings plays Dr Tim Finch
Who is Dr Tim Finch? One of four old school friends who come under suspicion of the murder of a teenage girl found buried under the motorway. He's a successful GP in a country town, happily married to his second wife, and has two daughters (Emma and Claire) from his first marriage who he's brought up himself.
Where have I seen Alex Jennings before? If you're a fan of British drama, you've probably seen Alex Jennings all over the place in recent years. He played Judge Edward Clarke in the recent Small Axe episode Mangrove. He is the Duke of Windsor in the first two seasons of The Crown and King Leopold in Victoria. Those aren't the only royal roles on his CV either, as back in 2006 he played Prince Charles in The Queen. Jennings also starred alongside Hugh Grant in A Very English Scandal as MP Peter Bessell, and played Alan Bennett in The Lady in the Van.
James Fleet plays Chris Lowe
Who is Chris Lowe? Initially one of the most successful of the four friends, with his own advertising company, a house in Notting Hill and a wife and a daughter, he has since suffered a change in fortunes and is now practically homeless – living in a camper van. He has battled severe mental health issues over the years.
Where have I seen James Fleet before? James Fleet is most famous for his roles as the bumbling Tom in romantic comedy Four Weddings and a Funeral, and as Hugh Horton in The Vicar of Dibley. More recently he's appeared as Reverend Wakefield in Outlander, and Bridgerton fans will recognise him as King George III.
Neil Morrissey plays Pete Carr
Who is Pete Carr? A failed businessman. He's never made much of himself, despite his ambitions and his years in Hong Kong trying to get his career off the ground. Having moved back to Norfolk and started a family, he's struggling to make a living as a salesman. He talks big, but he's just not up to the job.
Where have I seen Neil Morrissey before? The actor shot to national attention as Tony in Men Behaving Badly. Since then, notable roles have included Nigel Morton in Line of Duty, Eddie Lawson in Waterloo Road, Greg in The Good Karma Hospital, and Vincent Pike in Striking Out. He is also the voice of Bob the Builder.
Kevin McNally plays James Hollis
Who is James Hollis? Like Alex Jennings' character Dr Finch, James Hollis has managed to make something of himself. He is a journalist and TV presenter, with his own quiz show for sixth formers called Common Sense. James Hollis is a public figure who is very much in the limelight. He is a divorced man with a troubled son.
Where have I seen Kevin McNally before? You're most likely to know Kevin McNally from Pirates of the Caribbean, where he plays Mr Gibbs. His other credits include The Outpost (as The Smith), Designated Survivor (as Harris Cochrane) and Downton Abbey (as Horace Bryant). More recent projects include Das Boot, Catherine the Great (as Alexi Orlov), and The Crown (as Bernard Ingham).
Bronagh Waugh plays Jessica Reid
Who is Jessica Reid? The victim's identical twin sister. The girl's disappearance destroyed her parents and has left her with deep emotional scars and grief.
Where have I seen Bronagh Waugh before? You may remember her as Sally Ann Spector from The Fall. She's also been in Des, Lethal White, Derry Girls, and played Cheryl Brady in Hollyoaks.
Sasha Behar plays Jamila Faruk
Who is Jamila Faruk? Chris's love interest in the series, a Syrian refugee and a widow. The two of them met at a refugee centre and have known each other for about two years. Jamila is from a middle-class Christian Syrian family and is an interesting and intelligent woman. She has a son (Asif) but lost her husband in a bomb attack.
Where have I seen Sasha Behar before? The actress first appeared as Maya Sharma in Coronation Street in 2003. Since leaving the show, she's appeared in Strike Back, Luther (as Dani Lane) and both Casualty and Holby City (as Alex Broadhurst). She recently played the Seer in Da Vinci's Demons.
Indra Ové plays Maria Carr
Who is Maria Carr? Pete Carr's wife, and the mother of their two children. She's getting pretty frustrated at his inability to make a proper living and provide for his family.
Where have I seen Indra Ové before? She's appeared in Interview with the Vampire, The New Worst Witch, Midsomer Murders and The Dumping Ground. She recently played Maud in the Neil Gaiman/ Terry Pratchett adaptation Good Omens.
Siobhan Redmond plays Derran Finch
Who is Derran Finch? The ex-wife of Dr Alex Finch. Over the years she has suffered mental health problems and has lost contact with her two daughters, but Derran insists there is more to her ex-husband than meets the eye.
Where have I seen Siobhan Redmond before? Redmond's roles have included Beth in The Replacement and Bumalig Hightopp in Alice Through the Looking Glass. Other projects include The Nest and Grantchester.
Sara Stewart plays Mel Hollis
Who is Mel Hollis? The first wife of James Hollis, and a successful novelist. She was also in the holiday home on the night Hayley disappeared.
Where have I seen Sara Stewart before? You may recognise her as Susie from Doctor Foster. Sara Stewart has also played a QC in EastEnders, Jean Shales in Fresh Meat, and was in a 2005 episode of Doctor Who as the voice of Computer.
Tom Rhys Harries plays Elliot Hollis
Who is Elliot Hollis? The troubled son of James Hollis and his first wife, Mel. He leads an unstable life and frequently disappears on drug binges. At the moment he's experimenting with cross-dressing but seems deeply unhappy in himself.
Where have I seen Tom Rhys Harries before? The Welsh actor was selected as a Screen International Star of Tomorrow in 2012. Since then he's appeared in Jekyll & Hyde, Chewing Gum and Midsomer Murders, and starred alongside Ben Whishaw and Rupert Grint in a theatre production of MOJO.
Brid Brennan plays Suzanne Reid
Who is Suzanne Reid? Hayley and Jessica's mother. She has been unable to move forward since her daughter disappeared, paralysed by grief – and now she seeks closure and justice for her killer.
Where have I seen Brid Brennan before? Three-time Olivier nominee Brid Brennan starred in 1998 movie Dancing at Lughnasa alongside Meryl Streep. On TV she's been in Peaky Blinders, Come Home, Cracker and The Escape Artist.
Gerald Kyd plays Adrian Mullery
Who is Adrian Mullery? The victim's boyfriend, who was named as a suspect in the initial flawed investigation.
Where have I seen Gerald Kyd before? You may have spotted him in Cold Feet, Silent Witness, Humans, Sherlock or The Coroner.
Unforgotten season 2
Lorraine Ashbourne plays DI Tessa Nixon
Who is DI Tessa Nixon? Respected detective Tessa Nixon was married to the victim, David Walker, when he went missing. They had a son, Jason, who is now in his early 30s. Due to David’s depression, Tessa assumed that he had taken his own life or started again somewhere on his own. She has since remarried, living in the Cotswolds, and is on the brink of retirement when David’s body is discovered.
Where have I seen Lorraine Ashbourne before? Lorraine Ashbourne could almost call the Royal Exchange, Manchester her theatrical home, given she's played so many roles on its stage. The veteran actress has a decent TV CV too, with roles in Jericho, The Interceptor and Housewife, 49 to name but a few. And you might also have spotted her on the big screen in films such as Fever Pitch and Jack and Sarah.
Douglas Hodge plays Paul Nixon
Who is Paul Nixon? Tessa's new husband has been a great support to her over the years, but how will he react when her ex-husband's body is discovered? And what might it mean for their relationship?
Where have I seen Douglas Hodge before? Douglas Hodge is an Olivier Award winning stage staple who has famously enjoyed great success when starring in Harold Pinter plays. Chances are you've spotted him in Outnumbered, Only Fools and Horses or as Dr. Tertius Lydgate in the BBC's award-winning production of Middlemarch. He played Paul Burrell in biopic Diana, and Sir Robert Loxley in Russell Crowe's Robin Hood.
Will Brown plays Jason Walker
Who is Jason? Tessa's son Jason is a bit of a loner and his mother worries about him constantly.
Where have I seen Will Brown before? You may have spotted Brown on Call The Midwife or in Doctor Who series 9 episode The Highwayman.
Mark Bonnar plays Colin Osborne
Who is Colin Osborne? Colin Osborne is a highly-respected defence barrister who takes on a lot of pro-bono and community work, deeply caring about his clients. He lives in Brighton with his husband Simon: they're in the final stages of adopting a young girl, Flora. Before becoming a barrister, Colin worked in London as a high-flying banker.
Where have I seen Mark Bonnar before? From Line of Duty's Mike Dryden to Catastrophe's Chris and New Blood's Peter Mayhew, we've seen a lot of Mark Bonnar on our TV screens over the years. The Shetland and Psychoville star also appeared as Casualty's Bruno Jenkins. You may have spotted him in the likes of PhoneShop, Doctor Who and Home Fires, and more recently he's been in Quiz (as Paul Smith), and Summer of Rockets.
Charlie Condou plays Simon
Who is Simon? Colin's partner Simon seems blissfully unaware of his partner's woes and is fully focussed on bringing home their adopted daughter.
Where have I seen Charlie Condou before? Fans of Coronation Street will immediately recognise Condou as Coronation Street's Marcus Dent, but he had roles in the likes of Martin Chuzzlewit, Pie in the Sky, The Bill, Peak Practice and Urban Gothic long before that. He also made guest appearances in a number of British TV series including The Infinite Worlds of HG Wells, and Midsomer Murders.
Josef Altin plays Tyler
Who is Tyler? The mysterious figure seems to be following Colin and Simon – but why?
Where have I seen Josef Altin before? Game of Thrones fans will be familiar with Atlin, who played Pypar in the HBO series. He has also popped up in Top Boy, Chernobyl, River, Him & Her, Misfits and Being Human, as well as starring in a series of films including Les Miserables, Child 44, Eastern Promises and Boy A.
Rosie Cavaliero plays Marion Kelsey
Who is Marion Kelsey? Paediatric nurse Marion Kelsey works on a teenage cancer ward and has been known to develop close bonds with her patients. She has a tense relationship with her sister, Elise, and her mum, Joy, and had a turbulent time when she left home as a teenager herself. Marion is married to Tony but he suspects that she hasn’t been entirely honest with him about her past and is concerned about her mental health.
Where have I seen Rosie Cavaliero before? Rosie Cavaliero is one of those actresses who has popped up in just about everything. From Mid Morning Matters with Alan Partridge and The Enfield Haunting, to Cold Feet and Death in Paradise, she's starred in a lengthy list of primetime dramas. More recently she's appeared in Black Narcissus (as Sister Briony) and Worzel Gummidge.
Nigel Lindsay plays Tony Kelsey
Who is Tony Kelsey? Marion's husband Tony seems devoted to his other half, but often finds himself caught up in arguments between her and her sister.
Where have I seen Nigel Lindsay before? If you're a fan of Four Lions chances are you'll know Lindsay as Muslim convert Barry, but he's actually quite the accomplished star of stage and screen. He took the role of Shrek in Shrek the Musical at the Theatre Royal Drury Lane. You may also have spotted him in You, Me and The Apocalypse, Death in Paradise, and the BBC's historical drama Rome. And he played Sir Robert Peel in ITV's Victoria too.
Holly Aird plays Elise
Who is Elise? There's no love lost between Elise and her sister Marion - but why?
Where have I seen Holly Aird before? Cold cases are nothing new to Holly Aird, whom you might remember as Waking The Dead's original forensic pathologist Dr Frankie Wharton. She's had many minor roles in numerous TV series, and more recently played Franchise in A Discovery of Witches, but she's probably remembered by a generation for playing Nancy Thorpe/Garvey in Soldier Soldier.
Wendy Craig plays Joy Dunphy
Who is Joy? Marion's mother Joy is celebrating her 80th birthday when we first meet her and it's hinted that all is not right between mother and daughter.
Where have I seen Wendy Craig before? Beloved sitcom veteran Wendy Craig appeared in numerous films throughout her career but is best known for her appearances in the sitcoms Not in Front of the Children, Butterflies, And Mother Makes Three and And Mother Makes Five. She also played the role of Matron in ITV's Heartbeat spin-off The Royal.
Badria Timimi plays Sara Mahmoud
Who is Sara Mahmoud? Sara Mahmoud is an English teacher who is in the process of applying for a headteacher role at a struggling local school which she hopes to turn around. She is a practising Muslim and active member of her community but not afraid to ruffle a few feathers and challenge orthodoxy, particular when it comes to women’s equality. Sara is married with children but has secrets in her past that could jeopardise her family life.
Where have I seen Badria Timimi before? Fans of Doctors will recognise Timimi as Layla Darwish, while EastEnders viewers might recognise her as Doctor Sandra Vole, who cared for Jane Beale after Bobby violently assaulted her. She played Doctor Abraham in Hollyoaks, Doctor Allen in DCI Banks and another medical professional in Whitechapel.
Adeel Akhtar plays Hassan Mahmoud
Who is Hassan? Hassan is Sarah's loving husband, who just wants to see his wife happy.
Where have I seen Adeel Akhtar before? Another River veteran, the actor more recently played Lestrade in Netflix's Enola Holmes, and Thénardier in BBC One's Les Miserables.
He previously played Faisal in Four Lions. He also played Shahzad in the BBC Three's Murdered by My Father, and appeared in The Night Manager and Back to Life. Other roles include Utopia's Wilson Wilson and shopkeeper Ahmed in BBC mini-series Capital.
Unforgotten season 1
Tom Courtenay plays Eric Slater
Who is Eric Slater? Sir Tom Courtenay is wheelchair bound Eric, a former book keeper who worked at Arlingham House in the late 70s, and remembers the victim of the crime well. He is the carer of his much loved wife Claire (played by Gemma Jones), who has advanced dementia. Now long in retirement, Eric is in the process of organising a 40th wedding anniversary party, and trying to resist his son Les’ proposal that he and Claire move to sheltered housing when the series begins.
Where have I seen Tom Courtenay before? Courtenay is a legend of stage and screen, having first come to the world's attention in the 1960s in films like The Loneliness of the Long Distance Runner, Billy Liar and Doctor Zhivago.
Most recently he popped up in The Guernsey Literary and Potato Peel Pie Society, the Dad's Army film remake, The Golden Compass, and 45 Years.
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Trevor Eve plays Sir Philip Cross
Who is Sir Philip Cross? He has recently been appointed as the government’s entrepreneur Czar and has been happily married to his childhood sweetheart Shirley (played by Cherie Lunghi) for over 40 years. As the CEO of a successful retail company, he has always traded on his status as a self made man who started out selling from the back of a van down East Lane market. But the truth turns out to be more complicated and Sir Phillip has gone to great lengths over the years to cover up a past that he is deeply ashamed of.
Where have I seen Trevor Eve before? He may be best known for playing men of the law like Shoestring and Detective Superintendent Peter Boyd in BBC television drama Waking the Dead. The Olivier Award winner more recently appeared on screen in Death Comes to Pemberley as Judge Sir Selwyn Hardcastle in 2013, and as Roach in The Interceptor in 2014.
Ruth Sheen plays Lizzie Wilton
Who is Lizzie Wilton? Ruth Sheen is Lizzie Wilton, who lives in Croydon with her second generation Jamaican husband Ray.
Lizzie and Ray tragically lost their only son Michael at a young age. They are now both heavily involved in community projects helping local disadvantaged young people. Lizzie has a particularly close friendship with one of their most troubled kids, Curtis, who she is trying to help find his way in life. He’s attempting to resist peer pressure to join a gang. Cassie and Sunny will discover that Lizzie is a very different person to Beth Laws as she was known in 1976, when she was a troubled runaway living on the streets.
Where have I seen Ruth Sheen before? The Mike Leigh movie veteran - she's been in six including Mr Turner, Secrets & Lies, High Hopes and Vera Drake – has recently starred in Brassic, The Woman in White, Moving On, and as the outspoken mother Sandra in the last episode of 1980s AIDs drama It's A Sin.
You might also know Sheen as Misfits' Maggie, Bramwell's Nurse Car, Maureen Tracy from Doc Martin, or from The Bill: She played four different characters in six different episodes between 1989 and 2004. She has also popped up in an episode of Inside No. 9.
Bernard Hill plays Father Robert Greaves
Who is Father Robert Greaves? Father Robert Greaves is a priest in a parish of Leigh on Sea on the South East coast. He has been married to Grace for 39 years and they have two grown up daughters Ellie and Caroline. Robert acted as chaplain to Arlingham House from 1972-1983, which is the reason he is interviewed as part of the investigation.
Where have I seen Bernard Hill before? You'll know him best as Yosser Hughes from Boys from the Blackstuff, Captain Edward Smith from Titanic, King Théoden in The Lord of the Rings film trilogy and the Warden of San Quentin Prison in the Clint Eastwood film True Crime. You may also have spotted him in period drama garb, playing the Duke of Norfolk in BBC drama Wolf Hall.
Unforgotten season four is currently airing at 9/8c on Sundays on PBS Masterpiece in the US.
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