Sky crime drama Under Salt Marsh has reached its gripping conclusion, with the six-part series revealing who killed Cefin and Nessa
Neela Debnath Screen Time Reporter
22:01, 27 Feb 2026
Under Salt Marsh: Official trailer from Sky
Crime drama series Under Salt Marsh has finally reached its conclusion, with the six-part, Welsh-set and filmed programme delivering a compelling finale.
Here’s a look at the key plot developments from the closing episode of Sky‘s Under Salt Marsh, featuring Yellowstone actress Kelly Reilly and Rafe Spall from Apple TV+’s Trying, reports Wales Online.
WARNING: This article contains spoilers from Under Salt Marsh episode 6.
Who killed Cefin in Under Salt Marsh?
Schoolboy Cefin Hill (played by Jack Thomas-Humphreys) was murdered by Mac Jones (Brian Gleeson) after the youngster visited Sunnyside and uncovered that toxic waste was being deposited into Morfa Halen’s seawall.
When Mac discovered Cefin, the youngster was in a dire state. His boots had already been damaged by the toxic waste and the boy was determined to alert others of his disturbing find, including his teacher Jackie Ellis (Reilly).
Nevertheless, Mac murdered him to prevent the youngster from speaking out and to conceal his sinister secret.
Kelly Reilly in Under Salt Marsh’s finale(Image: SKY)
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Who killed Nessa in Under Salt Marsh?
Nessa Taman (Amara Atwal) was also murdered by Mac after he discovered her in the toxic waste.
Mac informed Jackie Ellis (Reilly) and Eric Bull (Spall) that Nessa wouldn’t have survived her severe injuries from the toxic waste and that’s why he killed her in what he claimed was an act of mercy.
How did Under Salt Marsh end?
Mac was apprehended by police after he attempted to escape and was detained to answer for his crimes.
Bull instructed Jess Deng (Naomi Yang) to acknowledge in her report Ellis’ involvement in the case and that he’d do likewise in his report.
Deng announced that Bull would be subjected to an investigation, potentially leading to severe misconduct charges akin to Ellis’ departure from the police force.
In the meantime, as the storm subsided, the inhabitants of Morfa Halen attempted to restore normality following the flooding of their town when seawater overcame the protective barrier.
Regrettably, Carys Northam (Marilyn Cutts), sister to Osian Northam (Julian Lewis Jones) and proprietor of The Ship Hotel, perished in the storm. Her body was discovered by him and a rescue team, leaving him heartbroken.
Ellis finally found Cefin’s killer in Under Salt Marsh(Image: SKY)
Ellis’ baby was safe, and she finally disclosed the news to her boyfriend Dylan Rees (Harry Lawtey), who confessed he’d been aware for months and had been waiting for her to tell him.
Ned Bevan (Rhodri Meilir) remained unaccounted for following his altercation with Ellis, which resulted in him escaping on a boat just before the storm hit.
Ellis experienced a moment of vindication when Solomon Bevan (Jonathan Pryce) labelled Ned a “coward”.
He asserted that she was the sole individual who had attempted to discover the truth about Nessa and Cefin, whilst others in the community remained silent despite knowing things.
With Nessa and Cefin’s murderer apprehended, it appeared that Ellis could embark on a fresh chapter in her life alongside Dylan and their baby.
Bull expressed a desire to take a break from the police force, hinting at the possibility of joining his romantic interest Gareth Morgan (Dino Fetscher) on a trip to the continent to document wildlife in France.
Under Salt Marsh is streaming on NOW
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