In too many thrillers to count, the key scene, and the most suspenseful one, arrives when the hero or heroine, investigating a chemical spill or a murder or what have you, sits down at the computer and deep dives into a web search, the information-age detective work culminating in that inevitable “Aha!” moment of discovery. So here’s where the darkness leads.

There’s a sequence like that in “Another Body,” a groundbreaking, creepy, fascinating, and important documentary about a phenomenon that’s only going to grow in significance: the deepfaking of pornography. That means: the lifting of images of real people off the web, whose faces are then digitally grafted onto pornographic footage to create a fraudulent porn file that looks as real as reality. Boogie nights? Try steal-your-body-and-soul nights.

In “Another Body,” the central figure is Taylor Klein, a 22-year-old graduate student in engineering who this happened to. An acquaintance sent her a link to a pornographic video that was discovered online — and it had her face on it. Much of “Another Body” is devoted to Klein’s fear, anger, despair, and trauma in the wake of discovering this outrage. I would have said “crime,” except that she calls the state police and learns that creating a deepfake, even a pornographic one based on the lifting of someone’s image, isn’t a crime in Connecticut, or in most other states. (There are a few states where it is.) At the federal level, Section 230 of the Communications Decency Act states that companies are absolved of liability or any responsibility for this kind of image manipulation. There‘s not much that Klein can do legally, which only heightens her feeling of helpless violation.

But as Klein springs back from the shock and terror of what’s been done to her, she discovers something: There’s a woman she was friends with at school who this was also done to. And that gives Klein a hunch — that the mysterious perpetrator of the deepfakes is someone they both knew at college. (Our initial thought is that it could have been anyone on the worldwide web.) As Klein calls up the link and finds the porn site it’s attached to, she recognizes a familiar name in an adjacent link. A bit more exploration reveals that there’s an entire circle of women she knew at college whose images are all featured in deepfakes. This moment of revelation — it’s like something out of a horror film — is at once chilling and cathartic. It allows Klein to regain a measure of control over her fate.          

According to “Another Body,” the number of deepfakes that exist on the Internet doubles every six months. Researchers say that there will be 5.2 million deepfakes in 2024; 90 percent of them will be nonconsensual porn files of women. And that’s to say nothing of how the technology itself is advancing. The movie shows us eerily convincing examples of deepfakes created by what is, in essence, AI. Here’s Dr. Lecter approaching the camera in “The Silence of the Lambs” — except that he has Willem Dafoe’s face. Here’s JFK in an old black-and-white speech saying “Read my lips.” Here’s the unhinged Jack Nicholson from “The Shining,” except that we look closely and the face is Jim Carrey’s.

The reality factor of deepfakes is already startling, but it’s the very convincingness of it that lends deepfake technology a singular potential for abuse and corruption. Just think of how it can — and will — work in politics: the creation of false images that appear genuine enough to fool multitudes. (As it is, a disturbingly large slice of the American people believe that Joe Biden stole the election…with no evidence.)

The potential of deepfakes as a kind of reckless pornographic weapon is already in full swing. Celebrity deepfake porn is a growing industry. (The documentary flashes on a list of some of the female actors it has exploited.) And when it comes to doing this to ordinary people, the technology has the potential to ruin lives. At one point, there’s an exchange on the porn site Klein discovers that explains a bit of how porn deepfakes are made. You go into someone’s Facebook or Instagram account and scrape out about 150 images of them; that’s all that’s needed. I personally believe that porn deepfakes should be prosecuted under identity-theft law, but this is one case where the rules of our society are lagging miles behind the technology.

Directed by Sophie Compton and Reuben Hamlyn, “Another Body” is a small-scale documentary, intimate and personal rather than sociological. The movie doesn’t explore deepfake porn with the kind of how-it-works expert testimony that marked the very good Netflix documentary “Money Shot: The Pornhub Story.” “Another Body” sticks mostly to the anecdotal point-of-view of Taylor Klein and her college friend (and fellow deepfake victim) Julia Moreira, tracing the investigation that leads them to figure out that the deepfakes they were victimized by were created by Mike, a young man in their circle who was friends with many of the women. He was a particularly needy sort of friend, who used each of them as a kind of therapist, and when any of them got tired of it (which they did), he would turn on them. The deepfakes are, in part, his twisted revenge.

As Mike’s identity comes to light, the story becomes driven by equal parts fear and activism. Yet it’s also not that simple. About halfway through the 80-minute film, it’s revealed that Klein and Moreira, these two women who have spoken with such candor about their ordeal, are in fact hidden figures. Their names are made up; the place they went to college is not really where they went; and the images we’re seeing of them are, in fact, deepfakes, created by actors who have provided “face-veils.”

This disorienting reveal does several things at once. It covers up the subjects’ identities, which the film presents as a fundamental safety issue. It offers a graphic demonstration of how effective deepfakes can be. But it also makes the documentary we thought we were watching seem more distant from us. It brings it a step closer to drama and a step further from reality, making the whole thing feel eerily like a projection. “Another Body” tells a vital story of porn and privacy, but the movie also becomes an almost unwitting demonstration of how deepfakes create not just their own reality but their own uncanny valley, detaching us from the very thing they’re pretending to lure us inside of. What that’s going to start doing to all our brains is next-level scary.