I'm always up for watching a cinematic experiment. And Steven Soderbergh's career offers plenty: In between his more conventional Hollywood projects, the writer-director-cinematographer-editor has played around with digital HD, nonlinear narratives, nonprofessional actors and new distribution methods.

For his latest adventure, Soderbergh picked up a humble iPhone 7 Plus to shoot the psychological thriller Unsane. Visually, the results aren't pretty, but they're interesting. On the level of narrative and tone, the movie is a mess.

The screenplay, by Jonathan Bernstein and James Greer, pulls a bait-and-switch so clumsy that it suggests a bad student film. For roughly half the run-time, we seem to be watching a twisty psychological thriller about an unstable young woman named Sawyer Valentini (Claire Foy) who's dealing with residual trauma from a past stalking.

When Sawyer seeks outpatient therapy at a mental institution, she finds herself being forcibly committed. Is she the victim of a nightmarish bureaucratic web, or is she actually "unsane"? When Sawyer identifies one of the orderlies (Joshua Leonard) as the man who stalked her in another city, the suspense should shift into high gear. Is he, or isn't he?

Instead, the film abandons its tight focus on Sawyer and abruptly resolves the mystery. From there on, we're watching a lurid, borderline-silly thriller with plot holes that nobody seems to have cared enough to fill. A shoehorned-in element of social critique can't compensate for the lack of anything resembling genuine fear.

Perhaps the problem is that iPhone cinematography is not, to put it mildly, the best medium for creating the fluid shadows and tricks of the light that feed this genre. While Soderbergh's carefully composed, underlit shots are weirdly fascinating, they generate about as much dread as an instructional video.

The one exception is a climactic scene set in an isolation chamber whose monochrome walls approximate a black-box theater. Without background distraction, the two lead actors' performances finally catch fire. The film briefly even manages to resonate in the #MeToo moment, as Sawyer confronts the fear she's lived with for years.

From her first scene, Sawyer is not a nice or easygoing person. Far from being her downfall, however, her not-niceness is what enables her to fight back. In this way and others, the film takes an empathetic approach toward stalking victims, yet it never reconciles that sensitivity with the pursuit of cheap, exploitation-style thrills.

With her enormous, watchful eyes and tight jaw, Foy delivers a tense, layered performance that deserves more fully realized material. But, because her antagonist's character wavers from scene to scene, never really adding up, she's performing in a vacuum. Other supporting players, such as Amy Irving as Sawyer's mom and Juno Temple as a fellow patient, never rise above caricatures.

Perhaps Unsane was designed as a spoof of Lifetime-style women-in-peril movies. Sawyer's romance-heroine name, to which the script calls extra attention, certainly suggests so, as do some scenes involving buffoonish cops. But the film's absurd aspects don't mesh well with its flat, documentary visual style, or with the earnest points it seems to want to make about rape culture and profit-driven mental health care.

Good points, to be sure, but not ones the movie is ultimately equipped to drive home. In trying to be too many things, Unsane fails to meet the basic requirement of its genre — to make us look nervously over our shoulders. As experiments go, it's a failure, but Soderbergh failing at something new is still more fun to watch than filmmakers who don't even try.