Sarah (Alison Brie) is a socially awkward woman who never really grew out of her girlhood horse phase. It’s clear to everyone but her that she’s not really welcome at the stables anymore, but she visits her old horse Willow even more diligently than she visits her childhood friend who was injured in a riding accident.

But horses are the least of Sarah’s problems. She’s a sleepwalker and she’s finding that her troubling lucid dreams are starting to leak into her waking life. She’s losing time, finding her body bruised, and since she’s a big fan of supernatural shows, she’s prone to those kinds of explanations. Is she a clone? An alien abductee?

And what’s really interesting is when she meets a guy and he had to decide if he’s horny enough to put up with her crazy. Because it’s clear that her mental health is deteriorating. Whereas before she seemed quirky if cringy, now her behaviour is getting harder to ignore or excuse. Her boss Joan (Molly Shannon) hardly knows how to help her but she doesn’t have many other non-equine friends.

As things fall apart, so does the narrative structure of the film. It’s clear Sarah has been an unreliable narrator, but for how long? What’s real? We doubt ourselves and her story far more than she does.

The very talented Alison Brie produces and is co-writer as well; she owns this story because she has created it, crafted it. Sarah slides down a slippery slope, and the descent is gives Brie a chance to show a muscularity in her performance that we haven’t seen before.

I wish the film were a little more sure of itself. Director Jeff Baena is reluctant to come down on one side or the other but the ambiguity starts to wear thin and push the bounds of credibility. It was thoughtfulness and sensitivity that pulled us in, and we lose a bit of that toward the end. Horse Girl is for an audience comfortable with oddball films and open endings.