Editor’s Note: The following story contains spoilers for the ending of “Longlegs.”

Nothing ends happily for the people in “Longlegs,” Osgood Perkins‘ viral serial killer horror movie now finally in theaters from Neon. The stylish satanic thriller has been hyped to its last ounce of blood thanks to its smart marketing campaign and considerable buzz over Nicolas Cage’s titular murderer, a Satan worshipper with the face powder and wig of a long-ago-faded glam rocker. (Tellingly, lyrics from the ’70s English rock band T-Rex, led by Marc Bolan, who sure looks a lot like Cage’s Longlegs, punctuate the movie.)

In its last act, “Longlegs” reveals the supernatural powers of its title killer, who sends lifesize dolls into the homes of unassuming families that then put them into a murder-inducing trance. As the psychically inclined FBI agent Lee Harker (Maika Monroe) realizes, Longlegs has for decades been working in cahoots with her mother, a fearfully religious basket case who does the door-to-door duty of posing as a nun to deliver the dolls that compel fathers to murder their wives and children with common household objects. That’s because Lee’s mother Ruth (Alicia Witt) made a pact with Longlegs years before to spare her daughter’s life in exchange for becoming his accomplice. Ever since, Longlegs has lived in Ruth’s basement as “the man downstairs” ominously referred to throughout the film.

Longlegs’ — and ergo Ruth’s — final victim onscreen is Carter (Blair Underwood), Harker’s partner at the FBI, who is hosting a birthday party for his daughter Ruby (Ava Kelders). Once Harker awakens to Longlegs’ long-buried connection to her family, she shows up at Carter’s house to discover that he’s by now under the spell of one of the dolls, brought into his home by Ruth, sitting in the Carters’ living room. Harker can’t prevent Carter from stabbing his wife Anna (Carmel Amit) to death, but she manages to shoot her mother dead before the spell can make its way into Ruby’s psyche. Maybe. Harker, firing away as she does, runs out of bullets before she can destroy the doll.

It’s a harrowing scene that leaves Harker’s fate uncertain, though a just-before-the-credits sequence shows Longlegs (who’s already dead after brutally killing himself during an interrogation scene earlier) blowing a kiss to the audience with the coda, “Hail, Satan!”

While Carter’s gruesome killing of his wife happens in a kitchen offscreen, my question for Perkins was how he directed the young Ava Kelders in this moment. Remember how according to film lore, with “The Shining,” the five-year-old Danny Lloyd, who played Danny Torrance, was under the impression that Stanley Kubrick’s horror movie was a simple drama about a family living in a hotel. That kept him in the dark to some of its most sinister plot points, which of course involved Danny being terrorized by his alcoholic father (Jack Nicholson). But in 2023, when “Longlegs” shot, that’s not how you run a set with kids along with buy-in from their parents, who are along for the ride of the production.

“[Ava Kelders] gets the script. Her mom is an actress. Her mom reads the script. Her mom is there. I keep [her mom] on set for as much of it as I can,” Perkins told IndieWire. “No one needs to brutalize a kid’s experience. It tends to be that children who are actors are maybe just a little bit more dialed into the fact that it’s all pretend, but at the end of the day, it’s still a kid, and you protect them as much as you can. I don’t think she saw any blood on that day, if that’s what you mean. If you look at the cut of the movie, her shots are pretty isolated. I don’t think she saw anybody in distress.”

Perkins previously spoke to IndieWire about working with children to create the film’s grisly crime scene photos, which appear in montages as Harker’s investigation into Longlegs deepens. “Sometimes you’re like, ‘Eh, I don’t want to lay that six-year-old girl down on the ground and pretend she’s dead.’ That’s not the greatest thing that ever happened, but let’s just get it over with. You get the picture, you pick her up, you say, ‘Do you want a juicebox?’ And you keep going.”

Speaking of montages, a flashback involving Alicia Witt’s Ruth spells out in explicit terms how her deal with Longlegs actually works. It’s more exposition than may be expected from a movie that otherwise dwells in conjuring procedural evil in the shadows before taking a supernatural turn. That ending came out of conversations in post-production, from test-screening feedback to work with the producers and Neon.

“In the screenplay that we shot, and we have lots of footage, Alicia Witt’s character actually says a lot more on camera in various moments,” said Perkins, who shows Ruth in flashback, years ago, holding a young Harker (Lauren Acala) in bed, seemingly telepathically whispering her pact with Longlegs to her daughter via Witt’s voiceover. But that’s a lie, as Harker has long been protected by Ruth against the nature of her link to Longlegs, and here that flashback sequence plays like a fiction the movie itself is dreaming.

“[Alicia Witt] sort of says a lot of exposition on camera, and we shot it. It was laborious, and it takes a long time. Then, I don’t use any of it because at the end of the day, like you’re saying, it doesn’t play as well,” Perkins said to the notion that “Longlegs” could potentially offer too much explanation in its final third. But he said that choices over how much to explicate harken back to the film’s central theme: that mothers can tell lies out of love. (A bit of autobiography here: Osgood is the son of Berry Berenson, who kept secret from her kids the fact that her husband, “Psycho” star Anthony Perkins, was gay up until his death from AIDS-related complications in 1992, a year before “Longlegs” is set.)

“What we found in the editing room is that if the idea that I told you before is that mothers tell lies, well, that’s the same as saying mothers make up stories, which is the same as mothers tell stories,” Perkins said. “So it became storytime. We were able to sort of couch as much of the exposition in what was authentically true for me in the intention of the movie, which is ‘Mothers Tell Stories.’ And so it is one of those very happy things where you’re like, ‘Oh, right, that’s what it should have been all along.’ Thank God we have footage, and I can use a lot of what Alicia said as voiceover, and I can rerecord it, and I can sort of find that way of showing it. But yeah, it became, like I said, true for the intention of the movie: Mothers Tell Stories.”

“Longlegs” is now in theaters from Neon.