The following article contains major spoilers for Backrooms, including its ending.

Backrooms stormed the box office over the weekend, anointing its 20-year-old director Kane Parsons as a wunderkind auteur to watch. (He is the youngest-ever filmmaker to debut at number one.) The film is a real trip, to say the least: it’s essentially the feature-length adaptation of a series of viral YouTube videos created by Parsons when he was a teenager. They were eerie found-footage-style shorts exploring an endless, liminal parallel dimension—a labyrinthine mass of knotted corridors with urine-colored walls and flickering fluorescent lights, designed like a dreary office workplace from the ’90s. The movie extends what was once a spooky internet meme into a full-on, feature-length horror flick, one that is variously surreal, bizarre, and at points, completely terrifying. And the craziness keeps going right up until the end.

In the film, we’re introduced to Clark (Chiwetel Ejiofor), a depressed furniture store owner—and failed architect—who, following a brutal divorce, spends much of his downtime with a bottle in his mouth, watching a steady stream of unsettling infomercials on his TV. It’s in the basement of the store that he stumbles upon the parallel world.

He soon becomes obsessed with the backrooms, seemingly because his curious discovery has helped to fill the vacuum of meaning in his life post-divorce. He recruits two of his younger employees (Lukita Maxwell and Finn Bennett) to help him record the new dimension. But shit quickly hits the fan: a monster lurks in the backrooms’s cavernous depths, making a snack out of Bobby (Bennett) and pursuing Clark and Kat (Maxwell) deeper into the world’s unexplored, more terrifyingly distorted bowels. In the meantime, his therapist Mary (Renate Reinsve), concerned by Clark’s disappearance—some weeks after their last visit ended with him self-consciously ranting about the backrooms—comes to the furniture store, and herself phases through the basement wall.

She finds Clark, who has gone insane, and chokes her out. Which is where the climax really hits: she awakens tied to a chair in a glitchy dining room, also occupied by Clark and a handful of human-ish creatures who essentially look like people with surreal deformities, their faces appearing to melt, distort, or even infinitely replicate. (It is also revealed that he killed Kat off-screen and keeps her decapitated head in the fridge.) He theorizes that the backrooms are made up of the memories of the people who enter, and that the humanoids are themselves copies of previous explorers: incomplete, imperfect simulacra, constructed from memories of memories, much like the backrooms’ infinite halls and liminal spaces. Clark tries to force Mary to role-play a conversation with his ex-wife—a therapy technique that she had used previously in the film—which she initially plays along with, before telling him that he needs to take responsibility for the manifold character flaws that led his wife to leave.

This, at least for a moment, makes Clark realize that his actions so far have been… well, batshit, and he frees her. Then comes the final sequence of the film, a bizarro pile-up of events each more gleefully absurd than the last. For starters, Clark’s own deformed body double enters the room. Turns out it’s the monster from earlier in the movie, revealed to be a towering, cartoonish replica of Clark in the pirate mascot costume that he wore for corny ads to promote the furniture store—a quite-literally giant metaphor for his mountain of insecurities and self-doubt. Pirate Clark chomps a chunk out of Clark, seemingly killing him, and then pursues Mary throughout the maze of the backrooms. Eventually, they emerge in a trippy, alternative version of the furniture store, where Mary inadvertently sets off a gas trap which had been placed by a shady scientific organization, Async, observing the parallel world.