When codirectors Scott Beck and Bryan Woods started thinking about who could play the antagonist in their new horror flick Heretic, they knew he had to have a few specific characteristics. The film is about a man who lures missionaries into his home, eventually turning a pleasant chat about religion into a nightmare scenario. So he had to be able to disarm with charm and humor, before switching gears to become intense and terrifying. “He had to have these moments of feeling dangerous, of feeling safe, contradictory traits that had to coalesce into something,” says Beck.

Early on in the casting process, the pair landed on a surprising name — and they couldn’t let it go. “As soon as we thought about him we were like: ‘This has to be Hugh Grant,’” says Beck. “That’s the only person we could see in this role, because he checked all of those boxes.”

The idea of putting you at ease is pivotal to the movie and character. Heretic starts out with two young Mormon missionaries — Sister Barnes (Sophie Thatcher) and Sister Paxton (Chloe East) — who approach the wrong house while proselytizing door-to-door. At first, Grant’s Mr. Reed seems completely harmless. He wears a cozy cardigan, stumbles over his words, makes silly jokes, and offers his guests Cokes. His home is filled with the smell of a baking blueberry pie. But eventually, the cracks start to show, and Reed shifts to preaching his own beliefs before moving in a much more sinister direction.

The character was inspired by a mix of real-world figures, including notable atheists like Richard Dawkins and Christopher Hitchens as well as the cult leader Keith Raniere. The directors spent around four months emailing back and forth with Grant, as he picked apart the character, peppering them with questions about Reed’s origins and beliefs. “I think through those conversations the character started getting clearer and clearer to all of us,” Woods explains.

Raniere, in particular, influenced Grant’s take on Reed. Grant “was interested in the word salad that Raniere is capable of conjuring in a way that makes him almost feel smarter than he actually might be,” says Woods. “He also responded to the way he creates the illusion of listening, which makes him seem less threatening.”

The directors believe that Grant’s past work, particularly his early career as a bumbling romantic comedy star, help set the expectation that this isn’t a character to be feared. “Early in his career… he didn’t feel threatening at all in any of those roles,” Beck says. “But as soon as you’re putting him into a movie that has the aspect of a suspense thriller, and he’s starting to challenge in a way that you’ve never quite seen, it weaponizes what we otherwise know of him.” Woods adds, “We’re leaning heavily on his charisma and charm and all the things we know and love him for.”

In a lot of horror movies, it’s hard to believe characters will stick around in a dangerous situation. But in Heretic, you can understand it; the warning signs are subtle at first, and once they become more overt, well, it’s too late. And that’s due to Grant’s ability to showcase both sides of the character so convincingly, making his guests — and viewers — feel initially comfortable.

“He’s funny and open-minded, he wants to hear what they have to say,” Woods says of the initial dynamic between Mr. Reed and the two missionaries. “There’s this feeling of two young women that are talking to an older man who appears to be very knowledgeable about their religion and all religions. So we buy that they are sitting there and engaging in this topic. And their best play is to politely listen to him and then extricate themselves from the situation.”

There’s another aspect to Grant’s character that makes him scary, something that will be familiar to anyone who spends much time on the internet: he’s a debate bro. The film is about Reed convincing Barnes and Paxton of his own beliefs. Without spoiling the specifics, he holds a particular disdain for nearly all organized religion. The conversation with the missionaries is almost a game. He has studied for a lifetime so that he can anticipate their questions and defeat them with logic. Reed doesn’t have much interest in hearing what the sisters really have to say — he just wants to prove himself right, using all of the characteristics that Grant embodies so well.

“What scares us the most is somebody that approaches something with so much certainty that they’re unwavering,” says Beck. “The great thing about discourse and debates is that you’re actively listening. Something about the movie that we’re excited about is that we can throw in all of these questions and conversation pieces, and Reed can feel like that guy on Reddit.”

Heretic is in theaters on November 8th.