Claire Foy delivers a jangly, abrasive tour de force in Steven Soderbergh’s ragged psychological thriller (shot entirely on an iPhone camera, to nervy but murky effect). Although her character, Sawyer, is involuntarily incarcerated in a mental institution with a man who may or may not be her stalker, Foy never plays the victim. And it’s the propulsive force of her bracing spite and nastiness that allows us, for a time at least, to overlook the derivative story (Shock Corridor and One Flew Over the Cuckoo’s Nest loom large) and the gaping plot chasms. Ultimately, though, just because some of the characters struggle with basic logic, it doesn’t mean the film should.