Hollywood trembles in fear of the havoc the internet has wrought and will continue to wreak on its core business. Execs wake up in a cold sweat from a nightmare that blockbusters have been replaced by 30-second TikTok videos. And, yikes, they almost have. But perhaps the key to a prosperous future is collaboration. 

Enter “Backrooms”: a disquieting and smart new horror film from A24 that, for now, can only be seen in theaters, yet is the brainchild of 4chan and YouTube users. Its director, Kane Parsons, is just 20 years old and his movie is already an uncommonly hot title with the younger set. Eighty-eight percent of its packed preview night audiences around the country were under 35.

You can see why. While the main character of “Backrooms,” Clark (Chiwetel Ejiofor), is a sleep-deprived, middle-aged man whose dreams of being an architect have been crushed as irreparably as his marriage, a youthful energy pervades Parsons’ strange and engrossing journey into the unfurnished abyss.

The seed of “Backrooms” was planted in 2019 when a user posted an image on the website 4chan of an architecturally unsettling room — tinted yellow with fluorescent lights, patterned wallpaper, ceiling tiles and gray carpet. People wrote horror stories online about the picture, which led to the detailed lore of the Backrooms, a labyrinth of eerie spaces accessible by hidden portals around the world. 

Parsons turned the trend into a popular YouTube series with millions of views when he was 16. And he rooted his creation in documentary-style “found footage,” like “The Blair Witch Project.”

The director used that same on-edge aesthetic for his debut feature, which is set in no-smartphones 1990. Clark, who runs Cap’n Clark’s Ottoman Empire, a failing furniture store, stumbles into the Backrooms when he walks through a wall in his building’s basement. 

The confused man tells his therapist, Mary (Renate Reinsve of “Sentimental Value”), who has her own demons, about the messed-up oddity he’s found. And Clark sounds completely insane.

“It’s like the store just continues, I guess?” he says.

Paranoid and needing proof, he drags down his assistant Kat (Lukita Maxwell) and her boyfriend Bobby (Finn Bennett) with a camera to explore the mystifying maze. 

The trio doesn’t just discover drywall and chairs, however. Deadly threats lurk in the shadows. Their expedition turns into a fight for survival.

The areas get weirder and weirder. One is lit only by a Christmas tree with Pompeii-esque body mannequins buried halfway in the floor. Another is piled high with stinking clothes. There’s an industrial pool. Even though they are modern rooms, taken together they’re a marvel of production design.

The off-kilter, subterranean office vibe brings to mind the sci-fi TV series “Severance.” A mysterious company is involved here, too. But the Backrooms also evoke childhood memories, and our early fascination with basements, forts and secret hideouts — and the fear that comes with them.

It’s quite a coup for Parsons to start off his career with Oscar-nominated actors as skilled and deep as Ejiofor and Reinsve. 

The “12 Years A Slave” star has bloodshot eyes and a maniacal resolve as Clark, who gradually is subsumed by the alternate reality. There’s more than a bit of Jack Nicholson in “The Shining” to his trapped-indoors intensity.  

Mary, meanwhile, winds up in the Backrooms out of concern for her missing patient, and begins experiencing glimpses of her painful past. Reinsve’s calming demeanor fades to the shakes of a scared rabbit. It’s here where we start to get some idea of what this unusual dimension is. Sort of.

Both the strength and weakness of “Backrooms” is that it was born of a big concept. The most spellbinding and paralyzing aspect of Parsons’ film is its never-ending, creepy scenery that he’s shot so appealingly and menacingly — all inspired by a spooky image on a message board. 

The knotty explanation of the nature of the place, however, made me feel like I was back at Christopher Nolan’s “Tenet,” or like I just walked through a haze of smoke in Washington Square Park. And as the plot hurdles to a close and a so-so monster is introduced, we come out of the trance and back into a more familiar scary movie. 

Even so, this is an undeniably exciting and actually quite sophisticated horror flick, and a fantastic bow for Parsons. There are far, far worse rooms you can walk into at the movie theater than “Backrooms.”