'Longlegs' isn't based on a true story, but it has a surprising connection to one famous murder

• The buzzy new horror movie "Longlegs" starring Nicolas Cage isn't based on a true story.
• The studio Neon's marketing included a website about "The Birthday Murders" — but they're not real.

People can't stop talking about "Longlegs," the new horror movie from the indie studio Neon starring Nicolas Cage as a devil-worshipping serial killer.

The movie, from writer-director Oz Perkins, centers on Lee Harker ("It Follows" star Maika Monroe), an FBI agent with apparent psychic abilities who's pulled in on a long-cold case of serial murders all linked to one mysterious figure: Longlegs. As her investigation progresses, Lee realizes she has her own long-buried connection to the strange man who has for three decades somehow been influencing fathers to slaughter their families and then kill themselves — all while staying away from the crime scene himself.

The killings, dubbed The Birthday Murders, seem like they could easily have been ripped from the headlines of a real-life cold case, leaving some fans to wonder whether "Longlegs" was inspired by true events.

Is 'Longlegs' based on a true story?

There's a long history of hit horror movies that are (typically very loosely) based on real events, like how pretty much everything in "The Conjuring" cinematic universe was taken from the actual cases of Ed and Lorraine Warren, a real married couple who investigated supposed supernatural events.

"Longlegs" isn't one of those, but some fans might have been confused about that, given Neon's viral marketing campaign.

The studio built an incredible amount of buzz around the film, which has reached an impressive box-office milestone within a week of its release: it's made $30 million at the global box office so far, becoming the indie distributor's highest-grossing debut ever, according to Collider.

Neon's marketing included releasing a series of cryptic visuals and video teasers that perfectly captured the film's sense of dread and unease, without revealing any of the plot or character details. In fact, it wasn't even made clear this was a movie about a serial killer at all. All this intrigue meant that by the time the movie was in theaters, horror lovers were clamoring to see it to find out what it was actually about — and what part Nicolas Cage played, since he was entirely absent from the ad campaign.

Part of its viral marketing also included a website about the so-called "Birthday Murders," styled like a throwback '90s webpage. ("Longlegs" is set in 1995.) The killings of the 11 families in the film are all connected by the fact that the daughter in each family has a birthday on the 14th of any given month (hence the name "Birthday Murders"), and the presence of a note signed by Longlegs at each crime scene.

The website details each of the 11 cases (which, again, aren't real or based on anything specific), which is an added detail for viewers who only got quick glimpses of the case files in the actual movie while FBI agent Lee Harker (Maika Monroe) was reading up on Longlegs.

The Birthday Murders website looks like any number of actual true-crime forums frequented by people who like to talk about and dissect unsolved murders. There are even some extra Easter eggs on the site, like the contact page listing "Friend of a Friend" — which is how Longlegs introduces himself to Ruth Harker during his first encounter with Lee as a child, and how Ruth later introduces herself when she goes to Ruby Carter's birthday to kill Agent Carter's family.

So, to recap: No, Perkins hasn't named any real-life serial killers or murder sprees as inspiration for his movie. He did, however, name a very specific detail from one famous murder case as part of his inspiration for the creepy, demon-possessed dolls in his movie.

The 'Longlegs' director says his movie's dolls were inspired by a small detail in JonBenét Ramsey's murder case

Perkins has elucidated a long list of classic films that he took inspiration from for "Longlegs." In an interview with Business Insider ahead of the movie's release, he specifically referenced "The Silence of the Lambs" and explained that he set his movie in the 1990s "as a cheat, to get people to feel like they were watching 'The Silence of the Lambs' again," which similarly followed an FBI agent who becomes entangled with an enigmatic, very creepy serial killer.

In an interview with Inverse, Perkins also named "Se7en," Gus Van Sant films like "My Own Private Idaho," and even "Psycho" — which famously starred Perkins' own father, Anthony Perkins, as the iconic killer Norman Bates — as further inspirations for the tone and visual landscape of "Longlegs." But Perkins' inspiration wasn't solely taken from other movies.

In the ending of "Longlegs," Longlegs is revealed to be a Satan-loving dollmaker who handcrafts life-sized dolls that look just like the daughters of each family he kills. These dolls all have a strange metal orb inside their head, which somehow acts as a conduit to allow a demonic entity to possess it and exert control over the families, influencing them to kill.

Perkins told Inverse that his inspiration for the doll detail came from two places. One was a book called "The Golden Bough: A Study in Comparative Religion" by James George Frazer, which detailed how people can be magically affected by actions upon inanimate representations of them, like voodoo dolls, puppets, and other effigies.

The other unexpected source? JonBenét Ramsey's murder file.

"The murder took place approaching Christmas, and one present that the parents had gotten for JonBenét was a life-size replica doll of herself, wearing one of her pageant dresses," Perkins told Inverse of the detail he incorporated. "It was in a cardboard box in the basement, 15 feet from where she was killed, and there was something so insane about that, I'd cataloged it away."

JonBenét Ramsey was a 6-year-old beauty pageant queen who was found dead in the basement of her family home in Boulder, Colorado, in 1996. Her killer was never identified. Notably, a long, handwritten ransom note was also found at the Ramsey crime scene, which also seems to connect to "Longlegs" and its title character's penchant for leaving ciphered notes at the scenes of his murders.

"Longlegs" is in theaters now.