The Third Day Island Is Real — & It Has Its Own Storied History

Photo: Courtesy of HBO.
HBO's The Third Day is a pretty disturbing show. Premiering September 14, the limited series, split into two chapters, "Summer" and "Winter," takes place on a hard-to-reach island, Osea, inhabited by a cult-like group of mysterious townspeople.
In part one, "Summer," the island opens up to outsiders for an annual festival, a bacchanal of sorts, full of drinking, drugs, and other debauchery for one night only on the otherwise vice-free island. But despite this modern party, the island itself has some very old traditions and remains deeply rooted in them. The Osea people aren't totally civilized, and neither is the island, which is filled with oversized crickets, bloodied animals (potentially sacrifices?), and so much humidity. In episode 1, everyone ends up sweating and bloated from the combination of the hot sea air and the pub's endless stream of booze.
As Jess (Katherine Waterston) tells an intrigued and slightly disturbed visitor Sam (Jude Law) it “took a bunch of drunks here to build a perfect sober world." She's telling Sam this to get him to relax by letting him know that the island is safe, but she's also referencing some of the area's real-life history.
The series was filmed on an island off the coast of England that resembles the onscreen area in many ways: they're both called Osea, they're both accessible only by one causeway which floods and dries with the tides, and they both have a history with sobriety. The similarities between the real and fake Osea end there.
At the beginning of the 20th century, in 1903, a man Frederick Nicholas Charrington named purchased an island off the coast of Essex with the purpose of turning it into a rehabilitation center. His family had created a successful brewing business, Charrington Brewery, years ago in the early 18th century. But Frederick had a different calling in life; he disinherited his family's fortune and devoted his life to helping those in need, especially those struggling financially, in abusive relationships, or seeking treatment for addiction. He founded the Causeway Retreat which offered free rehab facilities for alcohol and opioid addiction. The patients would work on the island in exchange for treatment, creating, like Jess says in the show, a bit of a sober oasis.
Later in the 1900s, the treatment center became known as a celebrity rehab facility (Amy Winehouse went), until it was shut down in 2010 for accepting and treating patients without the proper licensing and registrations.
There have been a few other uses for the 380 acre island, though. Daniel Radcliffe flew there to film 2012's Woman in Black, and was used as a location for an episode of Superstar (Idols), the UK's version of American Idol. It also houses a state-of-the-art recording studio which Rihanna may or may not have rented out to work on her secretive new album in 2019. Charli XCX, The Weeknd, and Euphoria's Labrinth are also said to have recorded music there.
In 2019, the island welcomed The Third Day's cast and crew, going so far as to promote the creepy series on their Instagram (I do wonder if they have seen the show and the fictionalized mythology now marking their island).
Currently, Osea Island advertises itself as an idyllic and enchanted getaway, complete with private residences for guests. Cheekily, the island's tourism website deems the land is "whatever you want it to be," leaning into the surreal atmosphere its isolated location provides.
But despite its day time allure, Emily Watson, who stars as pub owner Mrs. Martin in the show, says the island still gave her the creeps. “On a clear day with a sunny sky, it’s beautiful," she told the Irish Examiner. "There’s amazing birdlife. But it’s got all these creepy hedge tunnels and it’s just got a sense that stuff has happened there.”

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