Adrian Grenier and Angela Trimbur in "Trash Fire"

“Say something comforting,” says Isabel (Angela Trimbur) at one point in “Trash Fire,” to which her boyfriend Owen (Adrian Grenier) responds, “That’s not my forte.”

He might as well be speaking for the film’s writer/director Richard Bates Jr., who isn’t of the mind to put an audience at ease. Oddly, this is maybe the happiest we ever see Isabel and Owen, who have entrapped each other in a relationship that grows more diseased by the day. Owen, prone to seizures brought on by the titular blaze that killed his parents and left his sister Pearl (Annalynne McCord) with 80% of her body burned, isn’t the most social of boyfriends, all but isolating Isabel in their lonely apartment after alienating her born-again brother (Matthew Gray Gubler) and any friends they could possibly have with a nihilist streak a mile wide.

Isabel, on the other hand, can at least feign interest in others, able to stand toe-to-toe with Owen when he launches into his latest bromide, but with too much compassion to completely shut the door on him when she knows he needs someone to take care of him. It’s deeply unsettling, especially in the way Bates Jr. makes clear there’s no way out of it for either of them, which necessitates a trip to visit Owen’s grandmother and sister’s place to come to peace with the past in order to move on.

Fionnula Flanagan, Adrian Grenier and Angela Trimbur in "Trash Fire"“Trash Fire” is Bates Jr’s third feature, following “Excision” and “Suburban Gothic,” and it is clear it would be a misnomer to call him a director of horror movies, but rather movies that have horror in them. With a predilection for master shots that leave nowhere else for the audience to look and direct address that place one in the crossfire of characters constantly aiming for the jugular in one another, the filmmaker’s confrontational style suggests that hell is other people and he’s quite adept keeping the flames rising in that regard.

He finds a particularly dark corner of it to mine in “Trash Fire,” where codependency feels as if it’s far worse a plague than even the charred skin that has condemned Pearl to live out her days in the care of her and Owen’s ultra-religious grandmother (Fionnula Flanagan), isolated from the rest of society. Although she’s formed a warped sense of the world, she comes by it honestly, unlike her brother who’s long used his independence since the fire and the guilt of leaving his sister behind as a justification for his cruel behavior. The twisted ties that refuse to be unraveled between Owen and his blood relatives and his girlfriend despite various transgressions are what’s truly scary about “Trash Fire,” and it’s impressive how Bates Jr. keeps the film compelling despite characters you’d rather not spend time with otherwise with kicky dialogue and a penchant for pushing things further than you’d think they’ll go.

Still, it may not be far enough for those hoping for a gorefest once Owen and Isabel arrive at grandma’s house, but “Trash Fire” nonetheless gets under the skin, investing enough in Isabel’s anxieties about the prospect of starting a family with Owen and Pearl’s interest in having someone new to interact with in Isabel to build up to continually unsettle. No small part of this is due to the nuanced performances of Trimbur and McCord, who find depth in roles that easily could’ve been one note – particularly McCord, an inspired choice who comports herself with a wispy voice and lithe frame to play Pearl as if she were an apparition. Though “Trash Fire” is punctuated by moments meant to shock, it’s that lonely feeling of people who don’t feel as if they can be seen, no matter what their physical condition is, that is most terrifying.

“Trash Fire” does not yet have U.S. distribution. It will play at the Sundance Film Festival three more times on January 24th at 3 pm at the Yarrow Hotel Theatre, January 29th at 11:59 pm at the Library Center Theater, and on January 30th at the Tower Theatre in Salt Lake City at 11:59 pm.