I’ve learned a lot since I started researching for this review. I learned there is something called “creepypasta” which are horror-centric urban legends or short stories created and then spread virally across the internet. Then I learned that the new film “Backrooms” was originally a YouTube anthological video series that was based on a creepypasta of the same name. I don’t pretend to fully understand how all of that works, but it does nonetheless.

The YouTube creator behind “Backrooms” is 20-year-old Kane Parsons. The success of his online creation has now blossomed into a feature film adaptation which he directs. It’s quite an accomplishment for a young man not even old enough to buy liquor here in the states. But don’t let his age fool you. Parsons proves to be a savvy young filmmaker with keen instincts and surprising courage, even if not everything in his debut feature fully clicks.

“Backrooms” is backed by several notable producers including James Wan, Shawn Levy, and Osgood Perkins. Parsons does the rest, carving out his audacious vision with the help of screenwriter Will Soodik and two fantastic leads in Chiwetel Ejiofor and Renate Reinsve. He uses every bit of his modest budget to shrewdly build upon his original online premise, expanding his claustrophobic and atmospheric world while adding in new layers of lore.

Ejiofor plays Clark, a failed architect who owns a struggling Santa Clara Valley furniture store called Cap’n Clark’s Ottoman Empire. While Clark’s professional failures have left him bitter and frustrated, his biggest difficulty is with his recent divorce which has left him alone, living in his store. When he’s not drowning himself in liquor, Clark attends sessions with his therapist Mary (Reinsve). But he doesn’t find much comfort in them. Meanwhile Mary has buried trauma of her own that can be traced back to her troubled childhood.

While in his store’s basement, Clark makes an astonishing discovery. He notices a glimmer of light shining through a long vertical crack in the wall. While investigating it, Clark phases through the wall, coming out in what resembles an empty office space bathed in an overwhelming yellow tint. As he explores further he finds what seems to be an endless maze of connected liminal spaces, many with slight distortions such as upside down stairways or furniture clipping through the floor.

Clark escapes back through the extradimensional door and rushes to tell Mary about the “backrooms”. But she doesn’t believe him. So Clark recruits his assistant manager Kat (Lukita Maxwell) and her videographer boyfriend Bobby (Finn Bennett) to follow him through the portal and record their findings as proof of its existence. But as the trio pushes deeper into the backrooms, they encounter something terrifying. Later, after receiving a concerning voice message from Clark, Mary goes to the store to check on him. She finds the portal door and unknowingly enters into the nightmare.

Despite how it may sound, the premise is an unnerving one, specifically once Clark discovers the backrooms. The top-notch production design routinely takes minimalistic spaces and creates something eerily compelling for us to set our eyes on. And the sheer mystery of it all, especially for those like me who are unfamiliar with the online material, keeps us engaged and on the look out for any clues. Also, the sheer commitment of both Ejiofor and Reinsve proves to be crucial in selling us on the story.

Unfortunately some of Parsons’ early choices bog things down during what should be key moments. Clark’s first encounter with the backrooms starts with a chilling sense of dread but turns into a lengthy time-muncher as we watch him slow-walk around rooms, down halls, through doors, and into more rooms. Later, during what is arguably the film’s most harrowing sequence, Parsons suddenly turns to a prolonged found-footage approach, even though it doesn’t make sense in the moment. I get that it’s a nod to the web series, but it shortchanges what could have been truly terrifying.

But part of what makes Parsons so impressive is that he never seems stuck in one mode. He’s consistently throwing in something new and unexpected. This is especially true in the film’s wickedly entertaining second half. It takes a truly gonzo turn as Parsons takes some wild swings that land with an impact somewhere between horrifying and hilarious. The intensity also ratchets up, culminating in a big final twist that turns everything on its head in a mostly satisfying way. In the final few minutes I was glued to every word, every hint, and every suggestion.

From all indications “Backrooms” is doing massive opening week numbers and that’s great to see. This sci-fi and psychological horror hybrid is the kind of highly original material that can energize moviegoers, and that certainly appears to be the case. It also ushers in a fresh, bold, and young new voice in Kane Parsons, who displays the kind of striking vision and go-for-broke confidence that leaves you eager to see what he delivers next. As for his debut, “Backrooms” is enthralling, aggravating, mysterious, and confounding. And after much deliberation, I can say with confidence that I pretty much loved it.