Is Yeast a movie, or a dare? Its official synopsis contains this brag about director Mary Bronstein’s level of experience: “Conceived and made by an actor with no concept of the language of filmmaking, takes traditional dramatic structure and throws it out of the window to be swept away by the street cleaners.” It’s less a pre-emptive defense than a come on, a tease designed to seduce a certain kind of audience into stepping up to the plate. But it’s not pure provocation. Even fans of Frownland (which Bronstein starred in under the direction of her husband Ronald) may not be ready for Yeast’s full-on assault on the senses. This is a film that not only seeks to dodge the audience’s comfort zone, but it actually, actively mocks it. It’s not just abrasive; it’s restless, punishing, totally juvenile in its humor and indifferent to narrative flow or niceties of image. It appears to offers moments of genuine redemption or closure, and then undermines those moments with prankish punchlines. It is resolutely indelicate, and often absurd. It’s a nasty little stink bomb of a film that’s going to instigate a fierce tug of war between supporters and detractors––if it doesn’t completely clear the room. I think it’s a laugh riot and a must-see. Consider yourself warned.

On some warped level, Yeast is a coming of age comedy. Bronstein stars as Rachel, a torturously needy, bullying, self-obsessed adult-age girl who comes to learn the hard way that she is not the center of the universe. After failing to force her roommate (Amy Judd) to join her on a camping trip with a long-lost friend (Greta Gerwig), Rachel watches both friendships disintegrate. She’s certainly not a passive spectator to the disintegrations, but she pretends to be. She’s the kind of girl who will ratchet up a bad situation until it seemingly can’t get any worse, and then feign to be oblivious to either the badness or her complicity therein.

It’s a frills-free production: hand-held video camera, natural light, minimal costuming and art direction. The actresses usually seem to be make-up free, and in a film in which each is asked to hold close-ups for an uncomfortably long time, it’s an issue that extends into the bravery of the performances. I like Judd a lot, and I don’t think I’ve ever liked a Gerwig performance better, but Bronstein’s facial contortions steal the show. These are showy performances for sure, the internal made unbearably external, but Bronstein manages to deliver nuance to the noise.

Is it a spoiler to say that there’s a shot that sums up the entire film in the trailer? It’s when Gerwig’s character rubs her middle finger across her right temple and Rachel asks, “Are you giving me the finger?” That’s what Yeast is: it’s a pretty girl with no makeup on, making a vulgar gesture, playing as though she isn’t, with a glint in her eyes that says she really is. It’s obscene, but in a sing-song, adolescent way that’s actually unsettling in its casual violence. This tonal raspberry-blowing may be most infuriating in the film’s last scene, in which, rather than allowing the character she plays to enjoy the peculiar dignity of hitting bottom, Bronstein the director points and laughs. We can argue over whether or not the is the “right” way to wrap up a narrative, but it seems totally in line with Bronstein’s overall project. Of course this film chooses a final, bratty gesture over a classy, emotionally resonant fadeout––dignity was never going to be on the agenda.

Yeast is not going to have an easy time of it on the festival circuit, nevermind beyond. Mary will be accused of aping her husband’s style and thematic concerns. Her inexperience, and especially her flaunting of it, will be used against her. There are valid criticisms to be made, concerning the almost unwavering shrillness of tone, the lack of aesthetic pleasure, the detestability of almost everyone on screen. But of the couple of dozen festival films that I’ve seen so far this year, this is only one that I can imagine someone walking out of for any reason other than boredom, and that’s an accomplishment in and of itself. In its refusal to be beautiful or gentle or twee, Yeast makes something like Hannah Takes the Stairs look like Juno. It may end up being more about its own unpleasantness than anything else, but even with that, there’s a sick genius that I’m really drawn to. Call me a masochist, but Yeast is my idea of a good time.