Sometimes I live out my nightmares in horrible episodes called sleep paralysis. It's a disorder where your mind is awake but your body feels completely paralyzed, as if something—or someone—is sitting on top of you, say an incubus, as urban legend would have it. It's kind of like night terrors, except it affects adults way more and episodes are more vividly remembered. At its worst, I've heard whisperings and felt shadowy figures pulling my legs out of bed; at best, I feel a lot of pressure sitting on my chest and I have a hard time waking up. It's something I've lived with on a semi-frequent basis since I was a pre-teen, but I haven't had the truly terrifying kind of the former in several years... that is, until Thursday night, when it came back with a vengeance right after I watched Beware the Slenderman.

As I was fighting to come to full consciousness, I saw the curtains in my hotel room shape-shift into a tall, faceless figure. Slenderman. He had crept into my dreams. I don't believe in this "Slenderman"—an Internet-created bogeyman—but Beware the Slenderman did creep into my conscience. And many others'. For two 12-year-old girls in Wisconsin, Slenderman was—is—real. It's because they believed in this tall, faceless creature (thanks to fake video footage, games, forums, and photoshopped images online) that they decided to carry out his deed and kill their friend. On Saturday, May 31, 2014, the two girls, Morgan Geyser and Anissa Weier, lured their friend Payton Leutner into the woods under the rouse of hide-and-seek, stabbed her 19 times, and left her for dead. Payton was found by a cyclist and was taken to the hospital and has now physically recovered. Still, the emotional trauma is one that can't be shaken off. It's a case that has terrified and fascinated the nation, and one that's so singularly 21st century. It's a shocking tale that tells the power of adolescent mentality (especially in a group) and Internet storytelling—and the unfortunate, dangerous consequences when not handled in the right way.

The new documentary explores the psyche of Morgan and Anissa, asking what actually drove them to do this to their friend, and why. It's an incredible anthology of the Slenderman origin paired with intimate interviews with the perpetrators' parents, who themselves are trying to understand their children. It doesn't condone the girls' behavior by all means but it does make an eye-opening case. I spoke to director Irene Taylor Brodsky about the case, how her perception of the girls changed, and who the real villain is here—if there even is one.

I get sleep paralysis sometimes and I got a really bad case of it after watching this. It horrified me. I swear to god I thought I was seeing Slenderman.
My editor had a lot of weird experiences when she was making the film.

Like what?
She would just have a lot of dreams, a lot of bad dreams. Sometimes she felt like he was in the edit room. Sometimes she would lock the door of the edit room. Sometimes she would sleep overnight in the edit room because she didn’t want to leave the building. She’d kill me if she knew I was telling you this. But she made an amazing film—the way she cut together the film gives this feeling of “he’s there."

It reminded me of how Rodney Ascher is doing horror documentary style. Because it’s a documentary format, and it's "real life," I feel like that gets to you more.
One of the things I want to clarify, in case it wasn’t clear in the film, is that the Slenderman content, including the opening scene when someone is stumbling through the woods, is all found footage from the Internet. This is not stuff we created. What we created is all the interviews, the moments when the families, all of the drone footage. But the interrogations, courtroom footage, all the Slenderman footage, all the fan art, that’s not ours. That’s all found on the Internet. One of the challenges of the film became crafting those together in a way that was mysterious yet revelatory.

It’s such a dark topic and such a sensitive matter. What was your approach going into it? I feel like the documentary sympathized a lot with Morgan and Anissa. Was that your intent going into it, or did you find yourself there afterwards?
First I want to say, because the film is told from the perspective of the perpetrator, one can’t help but to come out of the other end of the film with more understanding. Sometimes that can translate into a sympathetic or more of an empathic understanding, but I never made the film trying to condone what they did or somehow say that it was okay what they did because they believed in Slenderman. Obviously, we need to do everything we can as content creators, as parents, as good citizens to let children know that you can’t carry out these kinds of acts. But I think when I started the film, I didn’t know who I was going to focus on. I just knew I wanted to make the film because I was very interested in that psychic space the girls were in leading up to the crime. The victim’s family declined to be a part of the film.

So you did reach out to Payton's family?
I did reach out. But within a few months, I was okay with that because I realized a lot of the questions I was trying to answer didn’t have to do with the victimhood. It had to do with the impulse to want to do this to their friend and why and where that came from. So I looked to neuroscience, I looked into the Internet. I looked into centuries of storytelling in horror, particularly Grimm’s fairy tales. Serial video storytelling, photographing, audio recording, performance art—all of these things contribute to the myth of Slenderman. That, I think, makes him so much more visceral to these girls. He’s not just a two-dimensional character in a book. It’s like he’s a character in the book that not only has no photograph of him, so it’s all your imagination, but in the games he’s after you. You are looking for him, but then before you know it, he’s looking for you. The tables get turned very quickly. That’s a very sophisticated kind of storytelling because it’s not just a passive experience where the viewer is just going to be scared. It’s like, the more engaged the viewer becomes, the more they are kind of contributing, especially if they are contributing content. Then they are just perpetuating the myth more.

With a case like this, you can’t blame just the the internet or the game or the forum. In your mind what's the villain in this movie?
I think it’s so easy to want to have a villain, it’s totally human. You want to know there’s a villain. But I really don’t think there’s one single villain. I think it’s more of a perfect storm of the media, the age, the social isolation these girls were feeling, and also it’s important to remember that Slenderman is a good idea. He’s an idea. He’s a character that somebody thought of. He’s a good idea and part of the reason he’s such a good idea is that he could be totally shaped and formed into what you need him to be. It’s for the same reasons that certain cultures have their children play with dolls that have no faces. It’s because we want to spur the imagination of our children. We want to impose our own idea of what that doll could look like. That’s what Slenderman does for all of us. But it’s particularly effective for children.

One of the things I was so impressed by was all the access you got, like how open the parents were to talk to you. I understand that it was very difficult to get that access, but how did you convince them that you weren’t trying to make villains out of their children? How did you get them to talk to you?
They certainly didn’t agree to be part of the film right away. It took a few months. But the key thing I did was that I sent them films. I didn’t try to sell myself or sell an idea because the truth is I didn’t know what the film was going to be like. When I make documentaries I sort of latch onto an initial idea or impulse, and then I follow my subject regardless of where they lead me. So I showed them films I made in the past and I don’t know if that is what made them want to work with me, but I do know that they watched my films and ultimately they agreed to be a part of this. They saw that I worked a lot with kids and they felt assured enough to trust me.

What was the most surprising thing you found out about either yourself as a filmmaker or the case while making this?
I was not prepared for how much the parents would tell me about their children that was not perfect. Of course I expected them to be like, “Here she is in her sweetest outfit at age 6. She was really good at school.” I didn’t expect them to paint a more complicated picture of them. I felt like that is a really hard thing to do to a stranger who has a very large megaphone. I didn’t anticipate it. But I was delightfully surprised because I really took it to heart that they trusted me with that.

Lastly, why should someone go see this movie?
I think there’s something in this film for everybody. I think there is a true crime story. I think there’s a very dramatic tragic story about family and parenting. I think it’s a story about mental illness. I think it’s a story about our justice system. And I think it’s a story about the infinite creativity of the Internet. I come from more of the dramatically-driven, character-driven documentary background, so for me, I really love the opportunity to deal with something that was popular going on now.

Beware the Slenderman premiered at SXSW on March 11, plays more during the festival, and will air on HBO on a future date.