Could Steven Soderbergh ever really retire? Our most prolific and eccentric of Hollywood insiders rather suddenly announced his retirement five years ago, and cooler heads cautioned us to wait and see. The retirement turned into a “sabbatical”, which turned into directing two seasons of The Knick. His hiatus from feature films officially ended after four years—i.e., the average time we wait for a non-retired Paul Thomas Anderson to make a film—with last summer’s Logan Lucky. And even if you missed it, which I did, you didn’t have to wait long for his next release: Unsane, a thriller shot quickly and in secret on an iPhone 7.

Its horror roots are as old as Dr. Caligari: a woman who may or may not be crazy gets involuntarily committed to a mental institute where someone may or may not be after her. From there, it descends from clammy to lurid, stopping along the way for Soderbergh’s recurring theme of money as the blood pumping through America’s veins. But the less revealed, the better, because a large part of the film’s suspense is whether its pieces will actually come together or go flying decadently off the rails. As a genre experiment, it uses the idiosyncrasies of its tech to wonderfully eerie effect: the digital grain, the blooms of light, the warping of the depth of field, the uncanny clarity of an HD close-up with little or no makeup—everything that seems “off” is very much in the film’s service. The choice of format and framing can put you at an almost immediate unease, and so many unbalanced compositions feel like miniature prisons of their own.

Like most Soderbergh films, it doesn’t swing for the fences; its aspirations are to tinker, needle audience expectations, and provide entertainment for perversely curious cinephiles who wonder how the idea of “a movie” (one with a narrative, a genre, a star, etc.) can end up on screen feeling like such an anomaly. It works as well as it does because it’s the sort of potboiler that wouldn’t want higher production values if you offered them and would roll its eyes at you, as contemptuously as its heroine, if you asked if it was “art.” But there’s a long, storied history of respected filmmakers being influenced by disreputable, low-budget pulp. So if you’re wondering what a 21st century equivalent of those cult 1950s/60s/70s B-movies would be—brash, formally inventive, so trashy in some ways but clever in others, bouncing progressive politics off of pure exploitation—Unsane is it. So get a phone and get cracking; formal control is cheap.