Zach Cregger, who both wrote and directed the upcoming horror flick Barbarian, has revealed that his idea for the film stemmed from a book written by a security consultant. On the surface, the movie is about a woman named Tess (Georgina Campbell), who checks into her Airbnb only to discover that a stranger named Keith (Bill Skarsgård) has booked the house for the same night. Seemingly out of options, she decides to spend the night there anyway. Justin Long also stars as a character named Cale.

Though its official release isn’t until September 9, Barbarian first premiered at San Diego Comic-Con last month. Considerable buzz and fan theories followed, and so far, there’s a consensus that the movie takes some truly wild, unexpected, and disturbing turns. The vagueness in these reactions has only further increased the mystery surrounding Barbarian. The trailer disorients viewers with an erratic montage of an underground labyrinth, a concrete cell containing only a dirty mattress and a camera on a tripod, and flashes of violence while an emotionless narrator promises that “this is perfectly natural.” Yet, virtually nothing in those two and a half minutes works to explain the movie’s title.

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However, Cregger has provided a hint by revealing that Barbarian is based on a thought he had after reading a book called The Gift of Fear, a self-help book written by a security consultant named Gavin de Becker. Cregger explains that the book provides detailed examples of small red flags in men’s behaviors toward women. He set out to write a scene that included “as many of those little red flags that I would ignore,” and the scene eventually grew into Barbarian. Read the explanation Cregger gave at Screen Rant's Los Angeles screening below:

I'd read this book called The Gift of Fear by this guy, Gavin de Becker, who's a security consultant. And basically, he had written a lot of examples of behavior that men can do that often women are encouraged to ignore; little, tiny, microscopic red flags. And The Gift of Fear is him basically saying, "Pay attention to that little voice inside your head." Because a lot of times, when we bypass these little warning signs, it's to our detriment. Those warning signs can be innocuous things like a man complimenting a woman when she didn't ask for it, or doing her a favor that she didn't ask being done—or initiating physical touch, even if it's not sexual and in a non-sexual situation. There's all kinds of little things that you really should pay attention to.

I'm reading this, and I just had this realization that I never think about this sh-t. Because I'm a dude, so I don't have to consider half the population a potential threat. And it was just this "holy sh-t" moment for me.

I didn't want to write a movie; I just wanted to write one scene where I could load as many of those little weird red flags that I would ignore, but a woman probably shouldn't. I thought about a double-booked Airbnb, and you're stuck in a house with a man [Keith, played by Bill Skarsgård] late at night, and he's doing all those things. He's making you tea; you didn't want it... But that's kind of the joy of that scene: trying to decode him.

Keith leaning outside a door in Barbarian

If that’s not reason enough for horror fans to check this enigmatic question mark out for themselves, Long’s role, in particular, has been teased as something that “[required] Long to tap into an especially disturbing headspace.” If this is meant to imply that Long will be playing a villain this time around, Barbarian may be a far cry from the actor’s other horror outings like Jeepers Creepers or Drag Me To Hell. Long has also mentioned that he had to look for ways to “find some humanity” in his character.

Based on Creggers’ explanation, it sounds like Barbarian may fall into the subgenre of socially-conscious horror that has risen to the top of critic lists in recent years. Movies like It Follows, Get Out, and most recently Bodies Bodies Bodies have been praised beyond the blood and suspense for scaring audiences with the things they have to say about society’s glaring flaws. One can’t help but notice that the inspiration behind Barbarian is reminiscent of another recent bloodbath overflowing with social commentary: A24’s Men. Add comparing the two to the list of motivators to get to the theater on September 9.