Pascal Plante’s new film, “Red Rooms,” is difficult to endure. Few movies in recent memory have made something constructive of the serial killer motif; Mr. Plante’s is one of them.

“According to the Internet Movie Database,” he writes, “there are more than 5000 films or series” dedicated to the subject of serial killers. Podcasts, too, one hastens to add, and books, lots of books. A professor of criminology at Boston University, Heather Ann Mooney, cites the popularity of such diversions among heterosexual women and posits that they serve as preventative lessons on dealing with the male animal: “How do I learn what the red flags are?”

What might Professor Mooney think of the events outlined in Mr. Plante’s picture — that there are women who prefer the red flag? There are more appropriate forums than this one in which to explore hybristophilia: that is to say, an erotic attraction to individuals who commit crime. Let’s just state that serial-killer groupies are a thing. Mr. Plante points to how Charles Manson was inundated with marriage proposals up to his final days. Ted Bundy and Richard Ramirez also garnered fangirls.

A 17th century British poet, John Milton, wrote that “the mind is its own place, and in itself can make a heaven of hell, a hell of heaven.” Somewhere toward the beginning of that fraught dynamic is the protagonist of “Red Rooms,” Kelly-Anne (Juliette Gariépy). She’s sleek, young, and beautiful — a fashion model at the top of her game. She has a luxury apartment in a high-rise with spectacular views of downtown Montreal. Her living quarters are sparsely decorated. Two adjoining desktop computers are at their center.

Other than working out and quaffing protein shakes, Kelly-Anne spends her free time playing online poker — she has a gift for it — and following the trial of serial killer Ludovic Chevalier (Maxwell McCabe-Lokos). Everyone in Quebec is following the proceedings, but Kelly-Anne is more than a casual observer. She arrives at the courthouse before dawn with a sleeping bag in tow. Kelly-Anne wants to be first in line at the Chevalier trial; every minute counts.

Compared to another regular at the trial, Clémentine (Laurie Babin), Kelly-Anne is a model of restraint. Clémentine has traveled from the provinces without a penny to her name. She’s convinced of Chevalier’s innocence and will say as much to anyone within earshot. The reporters hunkering outside the courthouse focus their attention on the voluble Clémentine and her theories about how Chevalier is being railroaded by a corrupt political establishment. Kelly-Anne takes an interest in the young woman; they become friends.

What is it that Chevalier is on trial for? In a sweeping opening scene, we watch as the prosecuting attorney Maître Chedid (a masterful Natalie Tannous) lays out the extent of the crimes in her opening argument. The charge is that Chevalier, after kidnapping three adolescent women, proceeded to kill, rape, and dismember them in a so-called red room — an online forum in which interested viewers pay-and-watch. Welcome to the dark web. 

Two of the three videos have been recovered and will be shown to the jury during the trial. Is it possible to identify the masked figure in them as Chevalier? Clémentine is eager to see the films and is outraged when the judge rules that the general public will not be allowed in the courtroom on the day of the viewings. Kelly-Anne assures her that Chevalier can’t be identified in the films. Clémentine is taken aback: Just how is Kelly-Anne privy to information that hasn’t been released to the public?

“Red Rooms” is less about Chevalier and his misdeeds than Kelly-Anne and her increasingly erratic behavior. Once she’s recognized by an attendant in the courtroom, her reputation as a model takes a downturn and her career comes to a halt. All of which prompts Kelly-Anne to take extreme measures on the dark web to further pursue her fixations. Where these lead makes for a deeply unsettling film.

Serial killers are scary, but so, too, is the invasive nature of the internet. Mr. Plante has contrived a riveting provocation.