SPOILER ALERT: Do not read this story if you haven’t watched Episode 4 of “Our House.”

As London’s Machiavellian property market continues to feel like a real-life thriller, U.K. broadcaster ITV’s drama “Our House” capitalizes on every buyer’s worst fear of losing their hard-earned home.

Starring Tuppence Middleton (“Downton Abbey”) and Martin Compston (“Line of Duty”), the four-part Hitchcockian thriller from “Sanditon” producers Red Planet Pictures is adapted from Louise Candlish’s 2018 novel of the same name, and may actually be the only thing more anxiety-inducing than closing on anything larger than a garden shed within the M25.

Middleton stars as Fi Lawson, a woman who returns home after a weekend away to discover strangers moving into her house — and her husband Bram (Compston) and children nowhere in sight. The new owners insist that Bram and Fi have been across every part of the sale, but she has no recollection of any of it. And despite her most petulant demands to “Get the fuck out of my house!” the interlopers aren’t budging.

“It taps into a primal fear,” explains Belinda Campbell, joint managing director of Red Planet. “As we like to say, ‘An Englishman’s home is his castle,’ so homes are hugely important and they’re all bound up with our identity.”

Screenwriter Simon Ashdown (“EastEnders”), who adapted Candlish’s novel, also highlights the psychology behind owning property, particularly in a hot market like London, where the average asking price for a house in February was £667,000 ($872,000), according to housing portal Rightmove.

“Obviously, Fi and Bram are a middle-class couple, but they’re not super rich — they had a bit of money and bought into the market at the right time,” says Ashdown. “But over the years, the value has grown and they’re now sitting on a fortune. The sense of your status and importance is elevated in your head, but really, you just got lucky: It’s a bit of an illusion.”

What’s fascinating about property, says Ashdown, is that people have become so obsessed with it. So much so that in “Our House,” the idea of losing her lovingly restored Victorian home — sold for a cool £1.7 million ($2.2 million) — throws Fi into a tailspin. The real kicker is that such property scams, which see homes sold from right under the noses of off-site owners through identity theft, happen every year in the U.K. The book was inspired by one such property fraud case in 2015.

“Our House” premiered on ITV on Monday and aired every night through Thursday, with the finale drawing an audience of 3 million. The show garnered an average viewership of 3.2 million across the week, which is roughly in line with the 9pm slot average for an ITV drama that airs across the week. (The whole show was made available on Monday on catch-up service ITV Hub, which will soon become streaming player ITVX.)

“It’s a book that could have worked [at other broadcasters and streamers] as well, but we actually found that the process of adapting it to fit with ITV ad breaks was a really great discipline, because you’re building to hooks [constantly], and that’s how the book is written: With all these great twists,” says Campbell.

ITV, whose drama department is overseen by Polly Hill, has come to specialize in a brand of mainstream domestic thriller that has sold well globally. The broadcaster had a major hit on its hands in 2017 with “Liar,” a he-said-she-said drama starring Joanne Froggatt and Ioan Gruffudd. Froggatt was back on ITV in 2021 with psychological thriller “Angela Black,” about domestic abuse. Similarly, “Our House” tells the story of a disintegrating marriage through the prism of a stolen home.

A thriller element is often incorporated into the commercial broadcaster’s biggest dramas, simply because “it’s got to be quite propulsive,” explains Ashdown. “I enjoy that, building to hooks and making a show unmissable. That’s very seductive.” And certainly, as ITV focuses its efforts on its streaming footprint in the U.K., it will need to compete with the best of the global streamers to keep viewers coming back.

Of course, despite healthy ratings, there’s been select criticism of “Our House,” with some viewers highlighting certain plot holes in the show (the fate of shady Wendy, who initially blackmails Bram, for example, has left audiences puzzled). But if you look closely, “Everything does actually makes sense,” says Ashdown, who explains that Wendy ultimately fades away into the night after realizing her accomplice Toby (the charming Rupert Penry-Jones) has been murdered.

As for that divisive ending, Ashdown confirms that despite being put through the ringer for almost the entire show, Fi “probably does go down” for killing scammer Toby. After all, he laughs, “The truth is she has actually poisoned him.”

Distributed globally by ITV Studios Global Distribution, a U.S. buyer is still being secured for “Our House.”