Netflix has quietly unleashed one of the most chilling British horror series in years with Under Salt Marsh, a six-part folk-horror slow-burn that premiered on November 28, 2025, and has rocketed straight into the global Top 10. Directed by Ben Wheatley (Kill List, In the Earth) and written by Alice Lowe (Prevenge), the series stars Olivia Colman, Mark Gatiss, and rising talent Mia Tharia in a story that transforms the windswept Norfolk coast into a place of ancient dread. With a perfect 100% critics score on Rotten Tomatoes and viewers warning “do not watch alone at night,” Under Salt Marsh is being hailed as “The Wicker Man meets Midsommar with a British chill that gets under your skin and stays there.”
The plot follows Dr. Ruth Hale (Colman), a grieving London marine biologist who returns to her childhood village on the North Norfolk marshes to scatter her estranged mother’s ashes. What begins as a reluctant homecoming quickly unravels into nightmare when Ruth discovers the tight-knit community—led by the charismatic but unsettling Reverend Josiah Blackwood (Gatiss)—is preparing for “The Tithing,” a centuries-old harvest ritual tied to the treacherous salt marshes that flood twice daily. As Ruth digs into her mother’s hidden journals, she uncovers evidence that the village’s prosperity depends on a pact far darker than folklore: every generation, someone must be “given to the marsh.” And this year, the signs all point to Ruth herself.
Colman is devastating as the rational scientist whose skepticism crumbles under the weight of grief and creeping terror, while Gatiss delivers a career-defining turn as the softly spoken reverend whose sermons feel like lullabies and threats at once. Tharia shines as local girl Mercy, torn between loyalty to the village and growing horror at what’s coming.
Shot on location in the real Norfolk Broads, the series uses the landscape itself as a character: endless grey skies, whispering reeds, and tides that swallow paths whole. Wheatley’s direction is masterful—long, silent takes of the marsh at dusk that make you feel watched, and a sound design of distant bells and lapping water that burrows into your brain.
Critics are breathless: The Guardian calls it “the most unnerving British horror since The Wicker Man,” Empire says “it’ll haunt your dreams for weeks,” and IndieWire declares “Colman and Gatiss are giving performances that feel possessed.” Viewers are equally obsessed: “I finished all six episodes at 3 a.m. and still can’t look at the sea the same way” (@HorrorJunkie, 80k likes).
In a year of jump-scare fatigue, Under Salt Marsh proves slow-burn folk horror is alive and terrifying. Stream all six episodes now on Netflix. But maybe keep the lights on.
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