On a Friday afternoon in 1999, I went to the matinee showing of a movie that I knew barely anything about. The film ended, the credits rolled, the house lights went up, and no one moved for a very long time. As we stumbled into the daylight, someone verbalized what we were all thinking: Was that real?

Was it real? I wondered as I laid awake in bed that night, and for the next four sleepless nights. I knew it wasn't—afterwards I read a story all about The Blair Witch Project, how they made the initial film for $25,000, and how the distributors had spent millions on a viral ad campaign (before the concept of viral media existed) to make it seem like three filmmakers had disappeared in the woods. But, for some reason, when it got dark, none of that mattered. I was convinced I heard the rustle of leaves or a faint moan emanating from somewhere outside my apartment.

It didn't help that I had new neighbors with bumper stickers on their car that said "Get Any Closer And I'll Eat You" and "Humans: The Other White Meat." Weird noises came from their apartment late at night. They were probably having sex, but I was convinced they were torturing people on the other side of the wall.

I was still not sleeping well a month later, when I left for a week at my childhood summer camp, which looked disturbingly like rural Maryland. The film had managed to make the most innocent images malicious: a pile of stones, a bundle of twigs, a few lines scratched upon a wall. Walking through the Michigan forest, I saw them all and shuddered.

I was terrified of something and I didn't even know what it was I was supposed to be afraid of. I was not able to be by myself after dark. I was 22.

Blair Witch not only perfected the largely improvised, documentary-style narrative which now makes up about half the shows on television, it also introduced the idea of found-footage, which has been mimicked in horror films in perpetuity from Paranormal Activity to Cloverfield. Add to all that the almost-exclusive reliance on hand-held cameras, which not only added to the authenticity, it provided a general uneasiness throughout the film. (When my mom saw it in the theater she walked out—not because she was a scaredy cat like me, but because the shaky camera nauseated her.)

Why Blair Witch remains one of the most frightening films ever made is precisely because of what all those so-called "reality" techniques don't show. The found-footage and the first-person camera and even the low budget actually enabled a lack of information that allowed our imagination to fill in the blanks. It was the standard ghost story we'd all grown up with, but we were able to annotate it with whatever version of that story that had terrified us when we were seven. We wanted to believe. And we did. Some of us a little too much.

The film was a smash hit, grossing $250 million worldwide, and etching itself a place in cinematic history. It was a tough act to follow for everyone involved. However, director Eduardo Sanchez's new film Exists just got picked up at SXSW. It's about another myth: Bigfoot.

A few months after I first saw the film, I thought I was over my fears for good. But then two of my neighbors (not the flesh-eating ones) thought it would be funny to let themselves into my house one night and make noises until I came downstairs. One of them was standing facing the corner. I relapsed for a few more weeks. I've never been able to watch the movie a second time.

The Blair Witch Project is now streaming on Netflix. I am right now, 15 years later, getting the chills as I write this story. Maybe I'll get up the nerve to see it again one of these days.