When architect turned furniture store owner Clark (Chiwetel Ejiofor) finds a portal to a mysterious realm of “backrooms” in the basement of his showroom, he struggles to explain it to his therapist, Dr Mary Kline (Renate Reinsve).

“I found a place …”

This otherwise innocuous phrase becomes a chilling summary of the architectural horror conjured in Backrooms, the latest A24 thriller that takes us into the liminal spaces of offices, dead malls and other eerie places that exist neither here nor there. Kane Parsons, the 20-year-old director – the youngest ever to work with the studio – produced a series of YouTube shorts titled Backrooms using just the free 3D software Blender and Adobe After Effects. The series has now been turned into a feature-length film, although it retains its visual language and conceptual framework.

“Liminal spaces” are those places that seem to be in-between other places, or have been left behind by the world. They are what philosopher Mark Auge called non-places, “a space which cannot be defined as relational, or historical, or concerned with identity”. Architect Rem Koolhaas called them “Junkspace”. They are the leftovers produced by advanced modernism, where everything looked the same, and there was a dissolution of “place,” in favor of neutral, meaningless places such as airports and department stores. “We have been trending for a few centuries into a spiral of industrialism,” Parsons said on the A24 podcast. “We’re kind of getting stuck in this monoculture.”

As the preeminent liminal space, “backrooms”, including Parsons’s YouTube series, are a fictional fandom expansion pack of the dead malls of the early 2000s. In fact, the first image to bring liminal spaces into online conversation, posted in 2003, was from the renovation of a furniture store in Oshkosh, Wisconsin. With the emptying of the big box store, there is the liminal. Once the in-between spaces borne of the 20th century’s urban modernization – the junkspace of airports, supermarkets and most importantly, malls – go out of business, they become even more estranged from their surroundings, more devoid of traces of humanity. The mall is junkspace; the dead mall is liminal space.

Backrooms builds an entire world of this eerie setting. “There is probably no better symbol for that kind of monoculture than a drop ceiling,” Parsons said. The fluorescent-lit rooms endlessly replicate, taking Clark and Dr Kline deeper as they try to discern where that world comes from and who controls it. Parsons has a keen interest in what he calls “the laws of the universe that resulted in our consciousness being the way it is”, and wanted to capture the feeling of infinite bureaucracy on screen. Much like liminal spaces highlight absence, Backrooms generates fear through turning our attention to what is left out; nothing is known about which entities govern the endless space, what is going on beyond doorways and corridors, and what set of rules determines it.

This type of terror is reminiscent of giallo films including Suspiria and Inferno by Italian film-maker Dario Argento where the building becomes the monster. The surroundings embody some other spirit or evil, without completely revealing what it is. In both films, like Backrooms, the action takes place in nondescript rooms that form a labyrinth. The mental map that a viewer typically makes out of on-screen architecture becomes incoherent. Clark tries to draw maps of the backrooms, to no avail. The confusion adds to the suspense.

The combination of eerie and mundane is at the core of the horror in Backrooms. In similar TV shows such as Severance, Stranger Things or Dark, a portal draws us into a world where the rules are not clear. There is someone or some force governing the strange world. Is it a government operation? Interdimensional entities? Corporations with secret technology? Is it the laboratory of a time travel, MKUltra or UFO program? Or is it something more boring? The mysterious Asych company offers little explanation to Clark.

Architect Damjan Jovanovic calls this banality of everyday life “institutional uncanny”, or “the aesthetic name for what it feels like to live inside a world that has been brought into being by paperwork rather than by stories”. Artists Mat Dryhurst and Holly Herndon have coined the term “protocol art,” a practice that engages with the underlying rules that dictate how culture is produced, distributed and perceived in a digital age. These rules frequently manifest as algorithms, artificial intelligence models, computer protocols, platforms and various technological infrastructures.

The drop ceilings, the wallpaper, the yellow-tinged lighting all bring about the feelings of absence, in-betweenness, nostalgia and bureaucratic sterility. Like Fritz Lang’s 1927 classic Metropolis, it tries to make sense of a rapidly dehumanized built environment and its effects on the human psyche. “The artistic stages of architecture are ... primarily mental spaces,” notes architect Juhani Pallasmaa in describing Alfred Hitchcock’s Rear Window. “Architecture, too, leads our imagination to another reality.” Backrooms constructs a “building” on screen that captures these feelings of liminality, and brings us into that world.

In Backrooms, this journey is palpable, as we venture deeper with Clark into the mysterious construction below his store. The movie takes the infinite liminal space Parsons conjures from the internet, and continues the long romance between horror and architecture.

• Backrooms is out in cinemas now