Happy Valley And Slow Horses Stars Unite For Sky’s Dark New Crime Thriller – And Its Central Mystery Is Already Gripping
A young boy is found dead. A little girl disappeared three years ago. And as a devastating storm closes in on a small Welsh town, two former detectives must confront a mystery that could expose secrets buried for years.
Sky is bringing together an impressive line-up of British acting talent for Under Salt Marsh, a six-part crime thriller led by Kelly Reilly, Jonathan Pryce, Mark Stanley and Rafe Spall.
With familiar faces from Happy Valley, Slow Horses, Yellowstone and The Crown among its cast, the new drama has all the ingredients of a gripping mystery. But its most unsettling element is the possibility that two seemingly separate tragedies may be connected.
Set in an isolated coastal community with a troubled past, the series promises a tense investigation in which time is running out – and an approaching storm could destroy the evidence before the truth comes out.
A Horrifying Discovery Brings A Three-Year-Old Disappearance Back Into Focus
The fictional Welsh town of Morfa Halen is a community surrounded by dramatic mountains and an increasingly threatening sea. Its residents are already bracing for a once-in-a-generation storm when an even more disturbing discovery turns their lives upside down.
Former detective Jackie Ellis, played by Kelly Reilly, has left her policing career behind to become a teacher. But everything changes when she discovers the body of Cefin, her eight-year-old pupil, who appears to have drowned.
For Jackie, the tragedy carries a deeply personal connection.
Three years earlier, her niece Nessa vanished without explanation. The disappearance devastated the family and ultimately cost Jackie her career. Despite the passage of time, the case remains unresolved.
Now, with another child dead, the questions surrounding Nessa’s disappearance return with renewed urgency.
Was Cefin’s death an isolated tragedy, or is there something much darker connecting the two cases?
Jackie And Her Former Partner Must Confront The Past To Find The Truth
The investigation takes another turn when Detective Eric Bull returns to Morfa Halen to examine Cefin’s death.
Bull is Jackie’s former partner, and his return forces the two to face an uncomfortable history. Both have unfinished business with the town, and the possibility of a connection between the two cases leaves them with little choice but to work together.
Their challenge is bigger than simply identifying what happened to Cefin.
According to Sky’s official synopsis, Jackie and Bull must repair their fractured relationship and uncover Morfa’s long-hidden secrets before the approaching storm wipes away crucial evidence.
With the weather deteriorating and the investigation threatening to expose painful truths, the pair face a race against time.
The storm is more than just a dramatic backdrop. It adds another layer of urgency to an already disturbing mystery, placing the entire community under pressure just as its darkest secrets threaten to emerge.
The Vision Behind Sky’s New Six-Part Crime Thriller
Under Salt Marsh comes from writer, creator and showrunner Claire Oakley, who has built the story around the relationship between a community and the landscape surrounding it.
Rather than focusing solely on the investigation, Oakley wants the drama to explore the people caught up in it – their heartbreak, fears, ambitions and the secrets they have kept hidden.
At the centre of the story is Jackie Ellis, whom Oakley describes as free-spirited, compassionate and determined. Her character also possesses a steely resolve, shaped in part by the challenging environment in which she lives.
Oakley has expressed particular excitement about Kelly Reilly taking on the leading role.
Meghan Lyvers, Director of Original Series at Sky Studios UK&I, has also praised the project, describing it as a uniquely powerful drama. She highlighted Oakley’s storytelling and the series’ exploration of loss, resilience and community, while pushing the boundaries of the crime thriller genre.
Happy Valley And Slow Horses Stars Lead An Impressive Cast
The series has assembled a substantial ensemble of British and Irish acting talent, with several performers already familiar to fans of acclaimed television dramas.
The main 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
The combination of performers from Happy Valley and Slow Horses is particularly noteworthy, bringing together talent associated with two of Britain’s most popular crime and espionage dramas.
With Kelly Reilly leading the story and Jonathan Pryce, Mark Stanley and Rafe Spall among the key names, the production has secured a cast capable of bringing considerable depth to its troubled characters.
When Will Under Salt Marsh Be Released?
Under Salt Marsh is scheduled to premiere on Sky and streaming service NOW in 2026.
An exact release date has not yet been confirmed, with further details expected closer to the show’s arrival.
The six-part series will centre on three unsettling elements: the death of an eight-year-old boy, the disappearance of a young girl three years earlier and a community facing a storm that could erase the evidence needed to solve both mysteries.
For Jackie Ellis and Eric Bull, finding the truth may mean confronting everything they once failed to resolve. And in Morfa Halen, the secrets waiting beneath the surface could prove just as dangerous as the storm approaching from the sea.