Calling The Blair Witch Project a phenomenon is flirting with understatement. From the moment of its première at the 1999 Sundance Film Festival (where it screened as a midnight movie), Blair Witch was a full-steam word-of-mouth express, with people who’d just seen it grabbing those who hadn’t yet by their parkas and shaking them violently, insisting that they absolutely must. An innovative online marketing campaign—launched when the Internet was still a relatively new toy for the general public—followed, creating even more frantic wanna-see by making it appear as if the film were non-fiction. Found-footage horror, which had previously barely existed as a genre, became so popular that it’s still going strong 15 years later; there are movies in multiplexes right now that only exist because of The Blair Witch Project. Shot for an initial budget that’s been reported as less than $50,000, it grossed just shy of $250 million (closer to $350 million, adjusted for inflation), making it one of the most profitable films of all time. Its two directors, Daniel Myrick and Eduardo Sánchez, were even on the cover of Time. Apart from Paranormal Activity—a direct descendant—there’s been no little-indie-that-could sensation like it since.

Oh, one more thing: America fucking hated it.

Not everyone, of course. Critics were generally enthusiastic, and there were plenty of folks who had the same intense reaction as the Sundance audiences. (Believing the footage to be genuine was likely a factor.) If there were some means of determining the most violent movie-related backlashes, however, it’s a fair bet that The Blair Witch Project would rank somewhere near the top of the list. According to the polling service CinemaScore, female viewers 35 and older gave it a D-, while male viewers in the same age bracket awarded it a rare F. Move down to the 21-34 group, and it managed a C+, which is still basically “Thanks for wasting my time.” Even teenagers, surely the target audience, could muster only a lukewarm B. (CinemaScore grades are so absurdly generous as a rule that a B can inspire mass panic at a studio.) Speaking anecdotally, I can’t recall another film that inspired so much sheer anger from people who felt they’d been duped by hype. Promised the most terrifying movie ever made, they instead got three annoying people wandering through the woods being terrorized by piles of rocks and bundles of sticks.

Their complaints were justified. The Blair Witch Project is a great movie, but it isn’t a great horror movie. The only parts that can really be called scary—and even then, only for viewers who are more freaked out by the suggestion of an unknown threat than by actual monsters or killers—are the scenes shot in the middle of the night, which represent maybe 10 percent of the film’s total running time. Its effectiveness as horror was almost entirely dependent on the illusion that its three characters were real student filmmakers who actually went missing five years earlier, after recording this footage. Viewed today, when it’s a given that found-footage movies are entertaining hogwash—nowadays, some of them don’t even bother with verisimilitude, opting to cast familiar faces like Friday Night Lights’ Zach Gilford (Devil’s Due) and Mad Men’s Ben Feldman (As Above/So Below) rather than unknowns—Blair Witch’s efforts at spookiness seem almost adorably quaint. So little actually happens that it’s a wonder there were no riots reported when it opened in theaters.

Viewed from another perspective, however, The Blair Witch Project is one of the goriest movies ever made: It’s 81 minutes of nerves being slowly shredded before your eyes. The real horror lies in watching Heather (Heather Donahue), Josh (Joshua Leonard), and Mike (Michael C. Williams) gradually turn on each other as their circumstances grow bleaker, until there’s arguably no longer any need for a witch or other bogeyman to torment them. By night, the film is an unconventional horror flick that teases the audience with creepy totems, offscreen noises, and Heather shrieking “WHAT THE FUCK IS THAT?!? WHAT THE FUCK IS THAT?!?” while running blindly through the dark woods. By day, on the other hand, it’s a harrowing collegiate gloss on Jean-Paul Sartre’s play No Exit, in which three dead souls discover that their eternal punishment consists of being locked in a room with each other. The woods here are just a big, empty room, and the screaming, bickering, and blame-tossing isn’t a grating distraction from the main story. It is the main story.

“ The Blair Witch Project is one of the goriest movies ever made. It’s 81 minutes of nerves being slowly shredded before your eyes. ”

Is that what Myrick and Sánchez intended? Probably not, but it’s what their unusual production method ensured. Improvised movies aren’t that uncommon, but The Blair Witch Project is one of the only films in which the actors shot all the footage themselves while the directors were nowhere near the “set.” (Sometimes they were in the distance at night, making scary noises.) Donahue, Leonard, and Williams spent several days actually hiking and camping in Maryland’s Seneca Creek State Park, with little food, constantly interrupted sleep, and no real idea what the project’s endgame was. This resulted in a unique sort of quasi-Method acting: They’re always in character when the cameras are rolling, saying and doing whatever they think will work best dramatically, but genuine, unfeigned frustration, exhaustion, and even fear seep into their performances. That’s especially true of Heather’s famous flashlight apology near the end, which has a raw power (complete with dripping snot) that only a world-class actor could possibly have achieved without having just experienced 100-plus straight hours of a simulated nightmare. But it informs virtually every moment after “Heather,” “Josh,” and “Mike” realize they’re lost. What some viewers perceived as bad acting is in fact the odd sensation—unfamiliar at the time, now ubiquitous on reality TV—of seeing people whose efforts at acting are constantly under attack by their own emotions.

(Quick aside: Part of what makes this approach so unusually effective here is that Blair Witch, though ostensibly consisting of the footage these three kids left behind when they disappeared, has been trimmed down to the bone. Myrick and Sánchez, who edited as well as directed, are utterly ruthless about cutting away from any shot the instant it becomes less interesting; many of the film’s “scenes” last 10 seconds or less, especially early on. This makes no sense at all in terms of the found-footage conceit—Who’s supposed to have assembled it so efficiently? The people who found it? The witch?—but it serves both the pace and the actors extremely well. Any moments when fiction and reality weren’t in sync were tossed aside, and if that demanded the inclusion of a single line or expression ripped from its context, so be it.)

Subsequent found-footage horror movies learned their lesson from the Blair Witch backlash. Some are decent, most are wretched, but they all serve up an overt booga-booga every so often, usually in the form of a jump scare. Oblique, unseen malevolence has been tossed aside as counterproductive. Actually, even Blair Witch caved slightly in that regard: In the original version of the film shown at Sundance (and in some early press screenings, one of which I saw), the final shot, which shows Mike standing in a corner of the basement, silently facing the wall, had no explanation whatsoever. That was singularly eerie, but not many people enjoyed being so confounded, and Myrick and Sánchez wound up adding one more interview to the opening section (the only footage in the movie not shot by the actors), giving a friend an anecdote to relate that ties Mike’s weird passivity into the Blair Witch legend. The capitulation is minor, but telling. Like Nicolas Winding Refn’s Drive, The Blair Witch Project is an art film that was sold to the public as mainstream entertainment. The filmmakers tried to make it more accessible, but there wasn’t much they could do.

Now that the “scariest movie ever” hype has long since died down, it’s easier to see Blair Witch for what it is. The film’s most crucial scene isn’t Heather’s snot-nosed, half-faced apology, though that remains its most memorable. Nor is it the finale, despite a magnificently disorienting effect in which Heather’s final screams are heard faintly from the microphone in Mike’s video camera, even though the black-and-white images come from her 16mm camera. Nor is it anything involving the iconic twig men or the noises in the dark. It’s the moment when Josh takes Heather’s camera and points it at her, shouting while she struggles to maintain her composure. “Okay, here’s your motivation. You’re lost, you’re angry in the woods, and no one is here to help you. There’s a fuckin’ witch and she keeps leaving shit outside your door. There’s no one here to help you. She left little trinkets, you fuckin’ took one of ’em, she ran after us. There’s no one here to help you. We walked for 15 hours today, we ended up in the same place! There’s no one here to help you. That’s your motivation. That’s your motivation.” Josh’s repetition of the phrase “There’s no one here to help you” turns into an abusive incantation that reflects their actual circumstances (in which the directors are nowhere to be found), and it’s not entirely clear whether he’s talking to “Heather” or to Heather, or which one of those two individuals is genuinely crying in response. More frightening movies than The Blair Witch Project are relatively easy to find. Horror movies this psychologically traumatic are in short supply.

Also today: Scott Tobias and Nathan Rabin analyze Blair Witch’s scares, its sometimes-clumsy imitators, and its sequel’s bad reputation, even among its own creators. And Thursday, Scott and Keith Phipps close the conversation with thoughts on the found-footage phenomenon, and where it can possibly go from here.