In the post-film Q&A for her second feature, Sarah Adina Smith referred to “Buster’s Mal Heart” as “an atheist’s lament.” It’s a story not so much of dual personalities, but of how a person (probably with mental illness) can evolve over time into somebody you don’t even recognize.

As the film begins, Rami Malek (in his first leading film role, cast here before the success of “Mr. Robot”) is on the run through a mountain range in rural Montana. Local law enforcement officers have been chasing him for years, knowing him only as Buster. He’s made a habit of breaking into empty vacation homes and taking up temporary residence. A favorite personality of one of the local morning radio shows, he frequently calls in with off-color warnings about the end of days.

Buster wasn’t always a hermit. Once upon a time he had a wife named Marty (Katie Lyn Shell) and a beautiful young daughter. He was the night shift manager in a small hotel, but that became part of his unraveling. By keeping long hours overnight and sleeping during the day in the home of his in-laws, his life wasn’t anywhere near where he hoped it would tbe. Grand plans of buying land and living off the grid are mentioned often, much to Marty’s disinterest.

As the film’s narrative shifts between these two different points in his life, we learn that his name is actually Jonah. The time period when he is working in the hotel is actually the late 90s. We get a sense of how susceptible that he can be to conspiracy theories when he becomes fascinated by a late night television host warning of how people are just “trapped in the machine.”

The tipping point for his sanity occurs when a man (played magnificently by DJ Qualls) shows up at the hotel late at night and explains a variety of end-of-the-world secrets to Jonah. A fascinating examination of how gradual the transition could be from “normal” to full-on Y2K paranoia, it’s actually quite easy to sympathize with Jonah’s struggles at first. Perhaps less so by the time he’s fully unbalanced and taking a couple hostage for Christmas when they make the mistake of coming to their guest house for the holidays.

Smith provides just enough comic relief and tender flashback moments between Jonah and his daughter for viewers to almost feel sorry for him as the storyline loops back around to those opening moments in the mountains. It not unlike when news reporters interview the neighbors of a person who did something awful and they say “he was a really nice guy” in disbelief. Did he suddenly become this person or were the signs there from the beginning? The success of the film hinges on Malek’s performance, which should appeal strongly to fans of his television persona.

The success of the film hinges almost entirely on Malek’s go-for-broke dual performance, which should appeal strongly to fans of his also-paranoid television persona.

“Buster’s Mal Heart” screens again at Fantastic Fest on Monday at 5:15 p.m.