Under Salt Marsh review: Rafe Spall’s Welsh crime drama is a gripping study of grief, secrets and isolation
A child is found dead in a drainage ditch. A storm is closing in on a remote Welsh town. And the detective returning to investigate has a complicated history with the woman who discovered the body.
That is the unsettling starting point for Under Salt Marsh, Claire Oakley’s six-part crime drama set in the fictional coastal town of Morfa Halen. Starring Kelly Reilly as former detective turned teacher Jackie Ellis and Rafe Spall as Detective Eric Bull, the series combines a tightly constructed mystery with a darker examination of grief, isolation and the secrets that can hold a small community together or tear it apart.
The series premiered on Sky and NOW on 30 January 2026.
A town under pressure
Morfa Halen is a place that seems permanently caught between land and sea. The town sits beside treacherous salt marshes, beneath dark skies and in the shadow of rising water. Its flood defences are already under pressure, while a major storm threatens to make them useless.
Warnings of a possible evacuation are being prepared as the weather deteriorates.
The setting gives Under Salt Marsh an oppressive atmosphere from the outset. The landscape is bleak, isolated and constantly threatening, and that physical danger mirrors the emotional state of the people who live there.
Jackie Ellis knows that feeling better than most. A primary school teacher, she has spent three years living with the disappearance of her nine-year-old niece, Nessa. Her life is already shaped by that unresolved loss when she makes another terrible discovery.
Walking home across the marshes one night, Jackie finds the body of one of her pupils, Cefin, who appears to have drowned in a drainage ditch.
The death brings Detective Eric Bull back into her life. Bull previously worked on the investigation into Nessa’s disappearance, and the hostility between him and Jackie is immediate. There is clearly a painful history between them, although the truth behind their relationship is rather different from what the familiar crime-drama setup might initially suggest.
That uncertainty becomes one of the show’s strengths. Under Salt Marsh repeatedly takes an apparent certainty and turns it around.
A murder mystery with something deeper underneath
Cefin’s death initially looks like a tragic accident. But small details begin to undermine that explanation.
A missing pair of blue wellies, part of a handprint preserved in the mud and differences between saltwater and freshwater all point towards the possibility that Cefin did not die where his body was discovered.
If he was moved there, someone else was involved.
That possibility also raises a much larger question: could Cefin’s death reveal what happened to Nessa three years earlier?
Oakley takes her time revealing the answers. At points, the pace is deliberately slow, allowing the marshes, distant mountains and empty stretches of landscape to dominate the screen. For viewers who enjoy atmospheric mysteries, the patient approach adds to the tension. Others may find themselves waiting for the investigation to move faster.
Either way, the clues continue to accumulate.
One of the most intriguing comes from Jackie herself. Among the schoolwork and other keepsakes she has preserved are drawings made by both Nessa and Cefin before they disappeared. Each child drew what appears at first to be an astronaut.
Cefin’s best friend James offers another interpretation. He calls the figure “the bee man”.
That leads the investigation towards Spider Island, where a group of people live according to the principle of living in harmony with the Earth. Among them is Kieran, played by Morgan Watkins, an apiarist who had already been questioned as a possible suspect in Nessa’s disappearance.
As Jackie begins connecting the histories of people in her hometown, the investigation exposes relationships and secrets that reach far beyond the death of one child.
Everyone has something to hide
The people of Morfa Halen have developed a strong sense of self-reliance, shaped by the town’s isolation and difficult environment. But the drama asks whether that independence remains useful when a community is confronted by a crisis that is too large to handle alone.
The pressure is both physical and emotional.
Osian, the unstable son of the local landlady, insists that the town is being poisoned. He also has an alibi for the night Cefin died, although his suspicions and behaviour ensure that he remains part of the growing web of intrigue.
Jackie, meanwhile, knows the town and its residents intimately. That knowledge allows her to uncover a truth that proves more painful for Cefin’s father than simply discovering who killed his son.
This is where Under Salt Marsh becomes more than a conventional murder investigation. The mystery is built around the connections between people: old loyalties, concealed histories, unresolved grief and relationships that have survived because nobody has been willing to expose what lies underneath.
Those connections can protect a community. Under enough pressure, they can also destroy it.
Jackie and Bull carry their own secrets
The central investigation is closely tied to the private lives of its two leads.
Bull is recognised unexpectedly by one of the men visiting from an environmental institute. The encounter makes it clear that the detective is concealing something important of his own.
Jackie’s relationship with the town is equally complicated. The way local people respond to her suggests that they know things about her past that she would rather leave buried.
She is also involved in a series of casual encounters with Dylan, James’s uncle, played by Harry Lawtey. But the relationship may be becoming more serious than either of them is ready to acknowledge.
Dylan also has an incompletely established alibi for the night of Cefin’s probable murder, adding another layer of uncertainty to a case in which almost everyone seems connected to everyone else.
The result is a mystery where suspicion does not fall neatly on one obvious outsider. The closer Jackie and Bull look, the more they uncover about the community itself.
Jonathan Pryce adds another mystery
Jonathan Pryce appears as Solomon, Cefin’s grandfather, whose presence hangs over the story even when he is not at the centre of the investigation.
So far, Solomon has had relatively little to do compared with the principal characters. At a town hall meeting, he demonstrates his contempt for the proposed evacuation by unleashing his sheep. Later, he leads the community in a hymn along the shoreline to commemorate his grandson.
Yet Pryce’s presence suggests that Solomon’s role is likely to become more significant.
His character adds another question to an already crowded mystery, particularly because the drama has established that the town’s history matters just as much as the crime itself.
A slow-burning thriller with a strong sense of place
Only the first two episodes were available for review, so the larger mysteries remained unresolved at this stage. Even so, Under Salt Marsh establishes the foundations for a psychologically focused thriller that uses its crime story to explore what prolonged grief and isolation can do to individuals and communities.
The landscape is central to that approach. Morfa Halen is not simply a backdrop for the investigation. The marshes, coastline, approaching storm and physical isolation all reinforce the sense that the characters are living under pressure.
The incoming weather also creates an unusually effective deadline. Evidence may disappear beneath the water, while the town itself faces the possibility of evacuation.
At the same time, the emotional storm has been building for years.
Jackie is still carrying the unresolved disappearance of Nessa. Bull has his own concealed history. Cefin’s family is dealing with a new tragedy. And the people of Morfa Halen are forced to confront secrets that have remained buried because the community has learned to live around them.
That combination gives Under Salt Marsh its particular character. It is a crime drama driven by clues and suspects, but it is equally interested in what happens to people when grief, secrecy and isolation become impossible to contain.
The deliberately measured pace may test the patience of some viewers, but the careful plotting and constant shifts in suspicion make the mystery difficult to dismiss. The series has already established a world where almost every discovery raises another question.
And with a storm approaching, time is running out.
Watch the official trailer
The official trailer for Under Salt Marsh was released by Sky ahead of the series’ 30 January 2026 launch. It introduces Kelly Reilly as Jackie Ellis and Rafe Spall as Detective Eric Bull and sets up the central mystery surrounding Cefin’s death, Nessa’s disappearance and the approaching storm.
Under Salt Marsh is a six-part crime drama created, written and directed by Claire Oakley, with Kelly Reilly, Rafe Spall and Jonathan Pryce among its principal cast.