Unsane

THRILLER; 1h 38min

STARRING: Claire Foy, Joshua Leonard

Along with being buried alive, being committed to a psychiatric facility against your will is enough to hang bats in anyone’s belfry. Times that by six figures when you discover that your long-term stalker (a diffident Leonard) is working there as a nurse; one of many developments so logistically dodgy it’s easier not to go there, and why bother when they’re all such a juicy blast?

Committed on the spot is exactly where Pennsylvania data analyst Sawyer Valentini (Foy) finds herself after what she thinks is a routine consultation with a counsellor classifies her as a danger to herself and others. There’s an insurance scam in the mix, but that’s incidental to Sawyer being constantly medicated, physically restrained, menaced by the loopy occupant of the bed next door (Juno Temple) and brushed off by condescending employees. Within days, she’s a nervous wreck — and after two years of being assiduously stalked, she wasn’t the most stable brick in the stack to start with.

“Maybe it’s all in my head?” she speculates, and it absolutely could be: for the first two acts, the seam of ambiguity in this grainy, shriek-generating, iPhone-filmed, Steven Soderberg–directed mare’s nest runs sufficiently deep to keep that pivotal question alive and thriving. By the time a revelling Soderberg (Erin Brockovich, Magic Mike) gets around to answering it, Unsanehas devolved into a different feral beast entirely.

Shrugging off the ermine mantle of The Crown’s Queen Elizabeth II with a vengeance, Foy is a one-woman force field. Her Sawyer transforms into a cornered warrior: spiky, resourceful, fearless in a crisis and curtly unafraid to look as crazy as she’s accused of being. The other lingering question in the darkness that envelops her is whether those watchful qualities will prove to be enough.