Archivist Dan Turner (Mamoudou Athie) gets recruited to reconstruct a collection of videotapes damaged in an apartment fire during the 1990s, hired by a mogul, Virgil (Martin Donovan), who might as well have “There’s More Going On Here” stamped across his forehead.Screening the footage in a remote location where the tapes are stored, Dan gets pulled deeper and deeper into the experience of a documentary filmmaker who shot them, Melody Pendras (Dina Shihabi). Her experiences take center stage much of the time, flashing back (mixed with the footage she shot) to her hanging around the building, trying to avoid provoking suspicions while examining rumors of some sort of cult operating there.The more Dan watches, the more the lines between past and present, between fantasy and reality, begin to blur, with the grainy video — and glitches that hint at the supernatural — compounding the difficulty in keeping them separate. That includes questions of what motivated Virgil to specifically seek out Dan, and assistance from Dan’s conspiracy-minded friend Mark (“How to Get Away With Murder’s” Matt McGorry), who is helpfully inclined to believe the worst.The challenge with something like “Archive 81” is to ensure the horror build-up occurs gradually enough so as not to send Melody or Dan screaming into the night before we can get to the “What’s really going on?” part. If the model for this is a movie like “Rosemary’s Baby,” it’s worth remembering those films didn’t tease out the reveal over eight parts.Under showrunner Rebecca Sonnenshine, that balancing act is achieved, perhaps inevitably, through dreams and fake-outs and other twists that create just enough fog to justify the investigators pressing onward.The reward for those with the patience to get there is that the explanation, when it does start to take shape, actually proves pretty compelling, introducing a dense backstory and possibilities for extending the drama beyond this opening salvo.”Archive 81″ draws upon very old horror themes, including whether seeing is really believing, and how evil might be hiding in plain view. Like the videotapes themselves, there are glitches along the way, but unlike some recent entries in this genre (hello, “Brand New Cherry Flavor”), not enough of them to provoke hitting the “eject” button.”Archive 81″ premieres Jan. 14 on Netflix.