Under Salt Marsh star was “shocked” by killer reveal: ‘It caught me by surprise, but I was like, ah, I see it’

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

Naomi Yang from Salt Marsh expressed shock at discovering who killed Cefin and Nessa, but acknowledged that the reveal ultimately felt logical.

The Sky Atlantic thriller takes place in the made-up Welsh town of Morfa Halen. The story begins when Jackie Ellis, a former detective now working as a teacher (played by Kelly Reilly), discovers the body of nine-year-old Cefin in a ditch.

Having experienced the pain of loss herself – her young niece, Nessa, disappeared years ago – Jackie believes there’s a connection between the two cases. However, Detective Eric Bull, a former colleague and friend, is hesitant to consider her theory at first.

As more details emerge, the link between them becomes clear, revealing a disturbing truth.

Yang, who plays DC Jess Deng, explained that truly great writing often surprises you at first, but then quickly feels perfectly logical.

Sometimes a surprising turn of events actually feels right and has a strong effect.

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.

Mac was secretly dumping toxic waste at Sunnyside amusement park, where major renovations were happening. With Dylan’s assistance, the waste was compacted and used as building material for a sea wall designed to shield Morfa Halen from storms and erosion.

Nessa and Cefin each discovered the illegal dumping ground separately, years apart, and were both injured by the dangerous materials there. Instead of calling for help, Mac, who found them both times, decided to kill them. He claimed they had witnessed everything and would have exposed him, and that their injuries from the waste – Nessa’s being life-threatening – meant he felt he had no other option to avoid further complications.

Nessa’s body was later discovered on the Bevan farm. Members of the family found her, but instead of reporting it to the authorities, they buried her to avoid trouble. Cefin, meanwhile, was moved to a drainage ditch.

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

Throughout the show, I kept guessing who the person connected to the community might be – I thought it could be Dylan, especially after his hair was found on Cefin, or maybe someone else. So, while the reveal was surprising, it also made sense when I finally understood it.

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

Yang explained that although Mac’s behavior was wrong and cannot be excused, it originally stemmed from his desire to protect his family and community.

She explained that he’s doing whatever it takes to protect the town. While he could have handled things differently, his actions stem from a deep love for his home and a desire to provide a good life for his family there.

When Jackie finally confronts him, you can see how desperate he is. He’s avoiding dealing with the consequences of his actions because they’re overwhelming.

He didn’t mean for things to turn out this way. He was actually trying to help – to do something good for his family and the town – but he lost sight of his original goal somewhere along the line.

Although Mac became preoccupied with his thoughts, Deng and Bull finished the investigation at Morfa Halen with a positive outcome.

Yang explained that initially, the power dynamic is clear: Bull is in charge, and she will follow his instructions. However, it soon becomes apparent that Bull has a personal connection to the situation – and is too involved, particularly due to his history with Jackie Ellis. This leads Deng to become entangled in the community’s issues, as well as the relationship between Bull and Jackie.

The ending is really powerful. He finally understands her perspective and acknowledges she was right to pursue the truth, even if it meant bending the rules and including Jackie. She, in turn, understands his motivations – it’s a deeply personal matter for both of them, and they finally connect on that level.

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

Both characters are very strong-minded, leading to initial conflict. However, when they finally find common ground, it represents significant personal growth for each of them.

“I might not agree with it, I might not think it’s right, but I can meet you halfway.”

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Under Salt Marsh airs on Sky Atlantic and NOW.

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Authors

Abby RobinsonDrama Editor

Abby Robinson is the Drama Editor at TopMob, where she writes about TV dramas and comedies. Before joining TopMob, she was a TV writer for Digital Spy and a content writer for Mumsnet. She has a degree and a postgraduate diploma in English Studies.

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2026-02-27 16:36