Cowritten by Alison Brie and director Jeff Baena, Horse Girl starts off as a basic quirky indie rom-com about a socially awkward girl named Sarah (Brie) who loves horses and supernatural shows starring Matthew Gray Gubler. But it quickly becomes a harrowing tale of mental illness as Sarah begins slipping into delusion and experiencing an acute loss of time. First come the nosebleeds, then the intense sleepwalking spells during which she does things like scratch the walls in her apartment or stand blank-faced in a deserted area clutching a pay phone. In a search for answers, Sarah combines Internet conspiracy theories with her family’s history of mental illness and rambles about aliens, time loops, and clones to those around her. But they all think she’s gone mad, which only makes her feel more isolated and paranoid. Brie’s performance is powerful and the film’s editing does a superb job of mixing Sarah’s obscured perception with reality, succeeding in offering an unsettling look into the mind of someone who suffers from a severe mental illness.