There isn't a concise� way to sum up the career of Steven Soderbergh. The auteur is always looking for ways to challenge himself and create new experiences for himself and his audiences (though we're not counting� those "Ocean's" sequels). Fresh off his short-lived retirement, Soderbergh returns with a new challenge: create a tense and claustrophobic thriller, entirely shot on an iPhone. "Unsane" is the director's latest experiment and it's an uneven, intermittent success.

Claire Foy (Netflix's "The Crown") stars as Sawyer, who is a data analyst at a bank. We learn quickly that Sawyer has a history of mental health issues, fueled by a stalker from her past. She's often quite guarded about her issues but sees a therapist to help talk them out. After signing http://bit.ly/2Phicmr - described to her as "boilerplate" stuff - she is involuntarily committed to a behavioral institution - aka, a mental hospital.

Sawyer's first objective is to convince everyone she� shouldn't be� locked up. The staff hears the same line from all their patients, so not much consideration is given to Sawyer's claims. She immediately clashes with one patient, Violet (Juno Temple), and finds an ally in another named Nate (Jay Pharoah). http://tinyurl.com/ydxqo68e of "Unsane" centers around who Sawyer can trust and who she can't, and the movie does a good job at keeping us guessing.

Things get a bit trickier for her when one of the orderlies (Joshua Leonard) reminds her of her stalker. As Sawyer begins to unravel at the sight of him, her case becomes more difficult to accept. The set-up of "Unsane" is far more effective than the back-half of the film, which ultimately spirals into conventional thriller. Still, Soderbergh knows how to keep us engaged.

The use of the iPhone is easy to write-off as a gimmick but Soderbergh uses it to build tension and keep us peering into Sawyer's world. "Unsane" is far more voyeuristic than Sean Baker's terrific "Tangerine," another recent film shot on an iPhone, which put us on the streets of Los Angeles. "Unsane" never feels as immersive.

Where the movie fumbles lies within the script by Jonathan Bernstein and James Greer. Most of the story is built on contrivances with no explanation, which leaves some unanswered questions about getting from point-A to point-B. The movie doesn't strive for ambiguity, hoping to keep the audience guessing, it merely takes a few easy shortcuts to get to the meat of the story.

As an experimental piece of filmmaking, Soderbergh succeeds as the director, building tension with the help of Foy's committed performance. Shooting her in extreme close-ups most of the time allows us to see her terror and frustration written all over her face. The pair keeps things alive when the story stutters due to its glaring issues.