Happy Valley And Slow Horses Stars Join Forces For A Dark New Crime Thriller Built Around A Chilling Mystery
A young boy is found dead. A little girl vanished three years earlier. And in a Welsh town already haunted by tragedy, the discovery threatens to expose secrets someone may have desperately wanted buried.
Two acclaimed crime dramas, Happy Valley and Slow Horses, are coming together through an impressive cast for Sky’s new six-part thriller, Under Salt Marsh. Led by Kelly Reilly, Jonathan Pryce, Mark Stanley and Rafe Spall, the series promises a tense investigation where an old disappearance and a devastating new case may be connected.
Set against an approaching storm and a community with plenty to hide, this is shaping up to be one of Sky’s most intriguing crime dramas of 2026.
A Child’s Death Reopens A Mystery That Never Truly Went Away
The story unfolds in Morfa Halen, a fictional Welsh coastal town caught between towering mountains and an encroaching sea.
Life in this close-knit community is already under pressure as a once-in-a-generation storm gathers offshore. Then former detective turned teacher Jackie Ellis (Kelly Reilly) makes a horrifying discovery: the body of her eight-year-old pupil, Cefin, who appears to have drowned.
But the tragedy brings back memories of another disappearance that devastated the town three years earlier.
Jackie’s niece, Nessa, vanished without a trace. The unresolved case cost Jackie her career, leaving wounds that have never properly healed.
Now, with Cefin dead, questions surrounding Nessa’s disappearance are impossible to ignore.
Could the two cases be connected?
An Unfinished Investigation Forces Two Former Partners Back Together
The discovery of Cefin’s body brings Detective Eric Bull back to Morfa Halen.
Jackie’s former partner returns to lead the investigation, confronting a community he failed once before. With the possibility that the two cases are linked, Jackie and Bull must put their differences aside and work together to uncover what really happened.
The pressure is mounting.
According to Sky’s official synopsis, the pair must reconcile and expose Morfa’s long-buried secrets before the approaching storm destroys the evidence for good.
The series combines a deeply personal investigation with the threat of an impending natural disaster, placing an already fractured community under extraordinary pressure.
The Creative Team Behind The Chilling New Series
Writer, creator and showrunner Claire Oakley describes Under Salt Marsh as a crime thriller rooted in a community’s relationship with its surroundings, with the heartache, fears, dreams and secrets of its people woven into the story.
At the centre is Jackie Ellis, a woman Oakley describes as free-spirited, compassionate and determined, with a steely resolve shaped by the landscape around her.
Oakley also expressed her excitement about Kelly Reilly taking on the role.
Meghan Lyvers, Director of Original Series at Sky Studios UK&I, called the project a uniquely powerful drama, praising Oakley’s storytelling and its exploration of loss, resilience and community while pushing the boundaries of the crime thriller genre.
A Star-Studded Cast Brings Together Familiar Faces From Hit Dramas
One of the biggest draws is the impressive collection of British and Irish acting talent attached to the project.
The cast includes:
- Kelly Reilly – Yellowstone, Here
- Jonathan Pryce – The Crown, Slow Horses
- Mark Stanley – Happy Valley, The Reckoning
- Rafe Spall – The English, Jurassic World: Fallen Kingdom
- Naomi Yang – Nightsleeper, Wolfe
- Harry Lawtey – Industry, Joker: Folie à Deux
- Dinita Gohil – Sandman, Greed
- Brian Gleeson – Bad Sisters, Phantom Thread
- Kimberley Nixon – Fresh Meat, Life and Death in the Warehouse
- Dino Fetscher – Fool Me Once, Foundation
- Lizzie Annis – The Witcher: Blood Origin, Extraordinary
- Rhodri Meilir – Pren Ar y Bryn/Tree On A Hill, Craith/Hidden
- Julian Lewis Jones – House of the Dragon, Wheel of Time
With performers from Happy Valley, Slow Horses, Yellowstone and The Crown sharing the screen, the series has assembled a cast with considerable experience in gripping television drama.
When Can You Watch Under Salt Marsh?
Under Salt Marsh is scheduled to arrive on Sky and streaming service NOW in 2026.
An exact premiere date has not yet been announced. Sky is expected to share further release information closer to the series’ arrival.
For now, viewers can look forward to six episodes centred on a devastating discovery, a three-year-old disappearance and two former partners racing against an approaching storm to uncover the truth.
