DS Eric Bull is a tough and seasoned police detective who always strives to find order among chaos. A long-standing cold case he couldn’t solve – that of young Nessa – is one that weighs on him heavily.

When tasked with returning to Morfa Halen, Nessa’s hometown, to investigate a new case, Bull has a score to settle both with himself and others.

But Eric has skeletons in his closet, cemented by a fractured friendship with Jackie Ellis, formerly his partner on the force.

As the investigation begins, an unusual bond unlocks parts of his past that’s shaped the man he’s become, forcing him to confront feelings he’s long buried.

Speaking ahead of the series launch, Rafe Spall talks about taking on the role of Bull, why working with Kelly Reilly proved to be too tempting to turn down, and what it was like facing the elements to tell this story.

What drew me in was the writing, the characters, and the chance to work with brilliant actors like Kelly Reilly.

Before I read the script, I was sent a character outline for Eric. It’s always interesting to see what people think you’re suited for. He struck me as a really compelling character — flawed, brooding, and complex.

The writing had an otherworldly quality, and the concept was gripping. It reminded me of Twin Peaks and True Detective, though it’s very much its own thing.

Eric’s a police officer from the Midlands — specifically the Black Country, which is where my mum and partner are from. It’s an accent you rarely hear on TV, and I wanted to bring that in.

He’s working class, ambitious, and haunted by a previous case in Morfa Halen, where he failed to solve a child’s disappearance. That failure still weighs on him.

He’s an outsider, and the town is wary of him. But I don’t think he cares. He’s there to do a job — find the killer. The case is personal for him, especially given his own childhood trauma. He lost a friend when he was young and feels responsible, so this investigation hits close to home.

Jackie and Eric were partners, though she outranked him. She’s no longer in the force — she’s a teacher now. Their relationship fractured when Eric arrested Jackie’s sister, wrongly suspecting her of involvement in her daughter’s disappearance. That destroyed Jackie’s family ties and her career.

Despite everything, they reconnect during this new case. It’s a platonic, deeply emotional bond — like siblings.

Deng, played by Naomi Yang, is Eric’s new partner. He respects her, but she annoys him. And I think that’s because she reflects parts of himself he doesn’t like. It’s a very human dynamic.

I’ve been acting professionally for nearly 25 years, and my process is quite private. I focus on staying relaxed and confident — that’s what makes a scene feel alive.

I sing before takes to break the tension. It’s not about presenting a character; it’s about making the moment real. Just be alive. Listen to the other person as much as you possibly can.

Claire’s brilliant. She’s smart, kind, and incredibly encouraging. She obviously had ideas about Eric Bull, about the kind of person that he is, but she was never prescriptive in how I should go about playing it. I used her original ideas of who he was as a foundation. But she’s been nothing but encouraging of what I brought to it.

Confidence is really important, and you need to feel like someone’s seeing what you’re bringing and then incubating it further. And she does that.

This is our third time working together. I did my second ever job with her, a play at the National Theatre when I was 18 years old, and later a drama called He Kills Coppers.

Kelly’s one of the greatest actors of her generation. She’s just a fantastic actor, person, and a pretty singular talent.

I wouldn’t say crime drama is my go-to genre, but I loved The Killing.

A good drama needs a strong plot, yes — but it’s the characters that sustain it. Audiences connect with flawed, relatable people. That’s what makes a story stick.

The storm in Under Salt Marsh is central to the plot — it threatens to wash away the town and all the evidence. Claire’s vision includes commentary on climate change, and sustainability was a big part of the production. But I’ll leave the deeper interpretation to her. I’m just helping tell the story.

Honestly? Not fun. I’m not into stunts. My ideal scene is sitting down, in the warm, talking, preferably in bed. I always joke that the perfect role is being in a coma — you still get paid!

But yes, the flooded set was tough. Saying that, I’m in an incredibly privileged position to be able to do it, I’m very grateful.

Very. Effing. Wet.