There’s a fun safety in horror movies that feature monsters or otherworldly creatures, because they don’t exist in the real world. But a horror movie based on a true story? That gives the movie an added layer of danger, because the story is based on something that really happened and could happen to anyone. Even you. Now the horror movie is terrifying on a whole new level.

Of course, it’s that precise reason that “based on true events” has been used as a scare tactic in horror movies that aren’t at all based on fact, like the brilliant marketing strategy that duped many into believing The Blair Witch Project was actual found footage. For that reason, this list excludes well known “based on true story” horror movies like The Exorcist, The Conjuring, or other beloved horror films centered around the supernatural- the authenticity can be debatable. This list also excludes movies that have taken drastic artistic liberties to the point where its inspiration is barely recognizable, like Psycho and The Texas Chain Saw Massacre.

Instead, we hone in on 10 great horror movies that got a lot closer to the true events that inspired them, with terrifying results…

Henry: Portrait of a Serial Killer

Between director/co-writer John McNaughton and Michael Rooker making his feature debut with an absolutely bone-chilling performance, this biographical serial killer film unnerves from beginning to end. In the film, Henry shares an apartment with Otis, a former prison mate, and they soon embark on a murder spree once Otis’ sister comes to stay with them. While it’s a fictional story, it’s based on real life serial killers Henry Lee Lucas and Ottis Toole. Both Henry and his accomplice were convicted of murder and received life sentences, and they both eventually died in prison.

Open Water

This survival horror movie follows an American couple, Susan and Daniel, who decide to focus on their relationship with a scuba getaway. On their second day of vacation, a miscount has the boat captain mistakenly think everyone is back on board and unwittingly leaves the couple stranded at sea. In shark-infested waters, no less. The story is based on the disappearance of Tom and Eileen Lonergan, an American couple accidentally left behind on a scuba trip in the Coral Sea. As with Susan and Daniel, Tom and Eileen weren’t discovered missing until two days later, where their belongings were found on the boat. Their bodies also were never found. Open Water attempts to fill in those gaps with its own theories, and used live sharks to do so.

Fire in the Sky

Based on Travis Walton’s book, The Walton Experience, Fire in the Sky follows a community shaken by the sudden disappearance of a local logger. He reappears 5 days later, seriously disturbed and with bizarre claims he’d been abducted by aliens. I know, I know. Alien abduction falls under the realm of paranormal and thus highly debatable. However, director Robert Lieberman and screenwriter Tracey Torme puts Walton’s story through the lens of his friends and family, and the police investigating the disappearance. It also leaves things intentionally up to the viewer, whether they believe Walton’s story to be fact or hoax. So, this movie doesn’t exactly count as a horror film in any way save for one gnarly scene; Walton’s flashback sequence that sees him waking from a cocoon on the alien ship and the subsequent experiments the aliens subject him to. It’s pure nightmare fuel.

The Sacrament

Ti West’s found footage thriller sees Patrick and his two co-workers embarking on a trip to Eden Parish, a secluded utopia, to film a documentary. Patrick was invited by his sister Caroline, a resident of the community to visit. Lead by the enigmatic Father, it soon becomes clear to the trio of friends that things aren’t all that swell in paradise. West’s screenplay may be a fictional story, but it’s based on the events of the Jonestown Massacre of 1978, right down to the cyanide poisoned juice.

Dead Ringers

David Cronenberg’s psychological horror film centers on twin gynecologists that take advantage of being identical to seduce women into falling for them both. The extroverted twin, Elliot, lures in the object of his desire, and passes her off to shy brother Beverly when he grows bored. The woman is none the wiser. But when Beverly falls for a woman who doesn’t return his affection, he slips into a drug-induced hallucinogenic madness. While this is a highly fictionalized version, it turns out that Eliot and Beverly were based on Stewart and Cyril Marcus, identical twin gynecologists who lived and worked together. It took weeks for their bodies to be discovered; a medical examiner ruled it was death by barbiturate overdose. The Marcus brothers shared everything together, including women, and slowly devolved into erratic behavior leading up to their deaths.

The Stepfather

Terry O’Quinn stars as the titular Stepfather, a serial murderer who targets single mothers, hoping to find his perfect family. When it doesn’t work out, he murders his new makeshift family, changes his appearance and skips town to begin anew. The Stepfather isn’t a true crime horror movie, but more of a slasher. It’s loosely based on mass murderer John List, though. In 1971, List killed his wife once his teen kids had gone off to school. Then he killed is mother, tied up loose ends, made himself a sandwich, and systematically murdered his children as they came home from school. He even went as far as to pick one up from school as if nothing had happened, before ruthlessly killing them. Then he disappeared, and no one heard from him again for 18 years. He was eventually found thanks to America’s Most Wanted, and the discovery that he’d long moved on and created an entirely new family was chilling.

The Serpent and the Rainbow

In Wes Craven’s film, anthropologist Dennis Alan is sent to Haiti to investigate the case of a man discovered alive seven years after dying and being buried. It’s this setup that provides the true story elements behind the voodoo tale. The film’s title comes from anthropologist Wade Davis’ non-fiction book of the same name, which presents the zombification case of Clairvus Narcisse. Feeling ill, Narcisse checked himself into a hospital and rapidly deteriorated until the doctors pronounced him dead. Over a decade later, his sister found him in the streets. Davis speculates that Narcisse had been given a powerful tetrodotoxin power by a black magic priest that had caused the “zombification.”

Wolf Creek

Writer/Director Greg McLean’s feature debut ruffled quite a few feathers upon initial release, including critic Roger Ebert, who was so thoroughly appalled by the brutal violence he lambasted the film. Wolf Creek introduces us to psychopathic killer Mick Taylor, who targets and tortures three backpackers in a film touted as being based on a true story. It not exactly a true story; it’s more like true stories. McLean actually pulls from multiple true crime cases for Wolf Creek. Ivan Milat slaughtered seven tourists between 1989 and 1993, and Bradley John Murdoch murdered an English backpacker in 2005; both killers informed the brutality of the film. McClean interwove Milat and Murdoch’s stories with the archetypical perception of Outback characters like Crocodile Dundee.

Angst

An unconventional, stylized Austrian horror movie that largely influenced Gaspar Noe’s work, Angst follows a psychopath as he’s released from prison and eager to commit crime again. After a botched murder attempt, the psychopath flees to a large house, and proceeds to torture and murder the three family members that live there. The psychopath is based on Werner Kniesek, a killer who brutally slaughtered a family of three while on parole. Director Gerald Kargl may have taken a stylized approach, but it’s an unpleasant, creepy watch.

The Girl Next Door

Based on Jack Ketchum’s novel, this horror film follows an adult David recalling horrific memories of his youth about a pair of orphaned girls sent to live with their aunt in his neighborhood. The girls are degraded, brutalized, tortured, and starved to death slowly at the hands of their aunt, cousins, and kids from the neighborhood while David struggles with whether to intervene. Ketchum’s novel is loosely based on the murder of Sylvia Likens, a 16-year-old held captive by her caregiver Gertrude Baniszewski. For a period of three months, Baniszewski, her children, and kids from the neighborhood subjected Likens to torture and abuse until she finally succumbed to her injuries. Baniszewski, her eldest daughter, one of her sons, and two neighborhood kids were arrested and convicted in the murder.