There’s a fun, emerging subgenre of horror that should feel particularly resonant for anyone who’s ever clicked “accept” on a long, incomprehensible set of terms and conditions, or signed a petition without really reading it. Let’s call it the “Don’t sign the contract!” film. Last year, there was A Cure for Wellness, where Dane DeHaan ended up taking a bath with some eels at a Swiss sanatorium after putting his John Hancock on a hefty stack of paperwork. This year, there’s Unsane, Steven Soderbergh’s queasy new thriller, where Sawyer Valentini (Claire Foy) tries to join a support group and instead finds herself trapped in a mental hospital.

The asylum is a classic location for scary movies, of course, but Unsane is more than a haunted-hospital tale. For one, it’s a warped parable about the evils of private health insurance, in which the scam that sucks in Sawyer seems to exist only to bleed her HMO dry. It’s also a chilling tale of toxic masculinity, in which a “nice guy” convinced of his own importance is the chief villain. Beyond that, though, Unsane is a great worst-nightmare movie from Soderbergh, a tense piece of low-budget auteurship that plops the viewer into an absurd scenario and then ratchets up the tension for the next 90 minutes.

Soderbergh announced his retirement as a filmmaker five years ago but never really stopped working; he just switched to television for a bit before returning to the big screen in 2017 with Logan Lucky. Unsane is very much in the mold of the low-budget, experimental films he’s pumped out over his career, including digital-video experiments like Full Frontal and Bubble, and cheap-yet-deep genre exercises like Haywire and Side Effects. Unsane was shot on an iPhone, and it shows; the visuals are harsh and uncompromising, but Soderbergh clearly sees that as part of the appeal. After all, this is a fast and dirty B-movie that goes right for the jugular.

As with other films that were also shot on an iPhone (like Sean Baker’s Tangerine), I quickly got used to the stark look of the photography. Indeed, the aesthetic is a good fit for Unsane’s plot, which unfolds like a series of furtive, conspiracy-theory videos that have been secretly posted on the internet—a missive from a dark corner of reality. It’s absolute nonsense, and yet the movie unsettled me more than any other thriller in recent memory.

Sawyer (a wonderfully intense Foy, who’s a continent away from her calm and collected Queen Elizabeth on The Crown) is a young professional who has moved to a new city for a new job. But she’s still haunted by the memory of her stalker, David (Joshua Leonard), a former client who grew unhealthily attached to her and developed powerful delusions about their relationship. Seeking to get past it, Sawyer looks up the name of a support group and heads out of town to a hospital in the suburbs, where she signs a contract agreeing to a psych evaluation. With that, her fate is sealed.

From then on, Unsane takes a few turns for the downright Kafkaesque. Sawyer is committed to an institution, having accidentally signed her life away. When her mother, Angela (Amy Irving), arrives to try and untangle the legal knot Sawyer’s in, the administrators give her the runaround, trying to bill her insurers for as long as they can. Everything Sawyer does is a violation of the rules and proof of her mental illness, as is every attempt to escape, and every explanation for her increasingly angry behavior. Then David shows up at the hospital, seemingly pretending to be a helpful new orderly asking her to take her medicine. Then Sawyer (along with the audience) starts to wonder if she’s truly gone crazy. Has she? One imagines Soderbergh tossing up his hands and replying, “Haven’t we all!”

Unsane is so mean and pulpy it could almost be a noir thriller from 50 years ago, but with enough topical import that it only could have arrived in this day and age. Here’s a horror film where the villain is a man who just won’t go away, and the prison Sawyer’s trapped in is just a symptom of capitalism’s death spiral, an amoral con designed only to take advantage of employee health plans. Sawyer has a friendly ally (played by Jay Pharoah) and a nervy enemy (Juno Temple) within the hospital, but in its last act Unsane becomes a true cat-and-mouse game between just her and David.

Soderbergh’s low-budget films often feel like a distraction from main events like Logan Lucky. This is the guy who once directed Out of Sight, The Limey, Erin Brockovich, Traffic, and Ocean’s Eleven in a roughly three-year period, so why would he waste his time on something that looks so chintzy? But, fortunately, Unsane is a perfect example of the kind of exhilarating results the director can achieve no matter what limitations he imposes on himself.