Under Salt Marsh star was "shocked" by killer reveal: 'It caught me by surprise, but I was like, ah, I see it'

**Warning: Major Under Salt Marsh spoilers ahead.**

Under Salt Marsh's Naomi Yang said she was "shocked" by the identity of Cefin and Nessa's killer, but that the reveal "makes sense".

The Sky Atlantic crime thriller is set in the fictional Welsh town of Morfa Halen, where the body of nine-year-old Cefin is found in a drainage ditch by former detective turned teacher Jackie Ellis (Kelly Reilly).

No stranger to loss herself following the disappearance of her young niece Nessa several years ago, Jackie is confident that the two tragedies are linked – something Detective Eric Bull, her former work partner and friend, initially refuses to entertain.

But as the facts of the case come to light, that connection is undeniable as the grisly truth is laid bare.

"I think it's always a sign of really good writing when you're shocked, but then immediately you're like, ah, it makes sense," added Yang, who plays Bull's current partner DC Jess Deng.

"Sometimes you're shocked because they've pulled it out of nowhere, but this makes sense, and it's really impactful."

For a full breakdown of Under Salt Marsh's ending, read on.

Under Salt Marsh ending explained

It was Mac (Brian Gleeson) who killed Cefin and Nessa – his own niece.

He is married to Nisha, who is the sister of Nessa's mother.

With Dylan's help, Mac had been covertly recycling toxic waste at Sunnyside amusements, which was undergoing a big regeneration project, crushing it down and using it to construct the sea wall built to protect Morfa Halen from the elements.

Both Nessa and Cefin accidentally stumbled across the illegal waste site, years apart, and were injured after coming into contact with the hazardous materials. But rather than call for backup or an ambulance, Mac, who was the one who found them on both occasions, felt he had "no choice" but to murder them. They had seen "everything", which would have been enough to put him behind bars, and they were already hurt by the waste – I had no choice, Nessa would have died from her injuries" – which would only have aggravated the situation.

Nessa's body was subsequently found on the Bevan farm – some of the family found her body during their own illegal waste operation, but chose not to report it to protect their own interests, instead burying her - while Cefin was moved to a drainage ditch.

Had they reported Nessa's body, Cefin might still be alive.

"You knew there was someone in the community, and throughout the series you’re like maybe it's Dylan [his hair was found on Cefin's body, via his nephew James], maybe it's this person, so it caught me by surprise, but also I was like ah, I see it.

"Gossip Girl, there was no clue there, but with Mac, it makes sense."

Yang went on to say that while Mac's actions are unforgivable, his initial actions were motivated by his love for his family and the town.

"The lengths people are willing to go to, he's trying to protect the town," she expanded. "It's coming from this place of–he could have obviously gone about it a different way, but it's coming from a place of love for his home and wanting to raise his family there.

"[And at the end, when he's confronted by Jackie] you can see he's desperate, he doesn't want to face what he's done because there's too much.

"But that wasn't his intention. He's trying to, in his own weird way, do a good thing for him and his family and the town. But he got lost somewhere on the way."

But while Mac lost himself, Deng and Bull came away from Morfa Halen investigation having gained something.

"At the start, the dynamic is, you [Bull] are my superior, and I will listen to you and do what you say," explained Yang. "But it quite quickly transpires that he's personally involved and too close given what happened before, especially with Jackie Ellis. And so then Deng can't help but get herself involved with the dynamics of the community, and Bull and Jackie's relationship.

"And I think by the end, it's so beautiful when they have that last scene, because he's sort of meeting her where she is, of like, okay, you do your report [ignoring protocol and involving Jackie], you were right. The truth needs to come out. And for her, she's meeting him halfway. She's like, I get it. It's personal."

Yang went on to say that she "never expected her to meet him there".

"They're both quite strong willed, which is why they don't really work at the beginning. But that moment where they meet in the middle, that's huge growth for both of them.

"I might not agree with it, I might not think it's right, but I can meet you halfway."

Under Salt Marsh airs on Sky Atlantic and NOW.

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