It’s Halloween, and some might say: “What an excellent day for an exorcism …”

It has been nearly 40 years since The Exorcist started terrifying moviegoers, and despite countless imitators and special-effects advancements made over that time, the 1973 film remains unparalleled as a terrifying and disturbing cinematic experience.

Stories from how it was made are almost as unsettling.

Director William Friedkin, who earned an Oscar nomination for the film, sat down with me for a Q&A this week after a screening of the film for the ICM Partners talent agency to discuss some of the most infamous legends surrounding the movie.

What’s surprising is how much of the story was inspired by true events – as difficult as they are to believe – as well as the sometimes bizarre lengths the cast and crew went through to bring William Peter Blatty’s best-selling novel to the screen.

Most chilling is the true story Friedkin learned at the start of the production…

1.) The lost diaries from a true-life exorcism

Friedkin says Blatty set out to write a non-fiction account of an exorcism that happened to a 13-year-old boy at a psychiatric clinic in 1949, but had to dramatize the story when it became too difficult to get specific details of what happened.

Those who did speak to Blatty requested that the character be changed to a girl, to help protect the identity of the boy who actually experienced the possession. Friedkin says that child grew up having no memory of the incident, and went on to an otherwise stable life. Friedkin said he recently retired from a long career at, of all places, NASA.

The filmmaker never met that man, but spoke with family members who described telekinetic activity surrounding the child during his apparent possession.

“The family was Lutheran and they went through all the stages you see in the film: they went to doctors, clinics, and finally went back to their own pastor in the Lutheran church, who recommended they see a priest,” Friedkin said.

It’s not that anyone in the medical profession actually believed a demon was the problem, but they thought the power of suggestion might help the boy if he thought it was a true possession. A priest named Father William Bowdern reportedly performed the ceremony, with a younger priest named William Halloran assisting.

The incident was even mentioned in Halloran’s 2005 obituary in The Washington Post.

When The Exorcist was in the early stages of production, Friedkin met with the Rev. Robert J. Henle, then president of Georgetown, who secretly passed him an old red folder with Halloran’s diaries and other eyewitness accounts of the true-life exorcism.

2.) Why would the Catholic church help The Exorcist?

You might assume the Roman Catholic Church would be viscerally opposed to seeing one of its more arcane rituals turned into fodder for a horror movie, but Friedkin says many church officials supported The Exorcist at the time.

Not only did Georgetown’s president, Father Henle, give them documents pertaining to the case, but the role of Father Dyer – the friend and confidante of faith-challenged Damian Karras (Jason Miller) – was played by a real priest, Father William O’Malley, in his one and only screen role.

“Most of the people at the highest levels of the church accepted it totally because the Roman Ritual of Exorcism is still in the New Testament,” said Friedkin. The director claims church officials later told him they credited the film for inspiring new applicants to be priests and nuns.

After all, the priests are the heroes of the story. And the message of the film is that there are some matters of the soul that science and medicine can’t fix.

“The Cardinal in New York preached about it from the pulpit and said great things about it,” Friedkin recalled. “The guy who was the head of the Jesuit order at the time, Father Pedro Arrupe, who was headquartered in Milan, he had his own print of it and would show it to his fellow priests and bishops and cardinals.”

Of course, not every cleric was a fan. “The cardinal in Boston loathed it and wanted it banned,” Friedkin said. “Billy Graham, who was not Catholic, denounced it from the pulpit and said ‘The Devil is in every frame of this film.’ Now, how he examined every frame, I don’t know.”

3.) What does The Exorcist’s filmmaker believe?

There may be truth to demons and possession, according to Friedkin – though he doesn’t pretend to know for sure.

“I did this film because I believe in the story. This film was made by a believer. The film to me is about the mystery of faith,” Friedkin said. “I know it’s voted this-and-that horror film, but to me it’s about the mystery of faith.”

Certainly a great many moviegoers believed it. The film caused a spike in people fearing they were possessed, and Friedkin said the movie’s young, doubting priest – actor and playwright Jason Miller (who died in 2001) – would often be accosted by people seeking to have their personal demons cast out.

“There was a lot of that,” the director says. “I used to walk down the street with Jason in New York and people would come up to him and try to touch his jacket. ‘Father, I have a son, I have a son …!’ And he would say, ‘I’m just an actor!’”

Stanley Kubrick once told Stephen King that he thought The Shining was an optimistic story – because it suggested there really was life after death. In a similarly twisted way, The Exorcist has the same message about belief in God, of course the devil is part of that package, too.

“Even if you call yourself an atheist, you have to think about it,” Friedkin says. “None of us has any answers. And as Hamlet said to his friend Horatio, ‘There are more things in heaven and earth than are dreamt of in your philosophy.’”

4.) Finding The Exorcist‘s demon child

The main character is a 12-year-old girl, an innocent corrupted by outside evil. But most 12-year-olds shouldn’t even SEE The Exorcist.

“I thought for a long time, we could never make this film. We couldn’t cast it,” Friedkin said. “We threw out a net for about 2,000 young girls. And we couldn’t find anybody who could even handle the subject matter.”

From his office at 666 Fifth Avenue in New York (an ironic address if ever there was one), Friedkin and Blatty had given up and started auditioning actresses who were in their late teens. Then 13-year-old Linda Blair and her mother came in without an appointment, hoping to get a shot at the part.

At that point, most of Blair’s experience had been modeling clothes for advertisements.

“She sat down with her mother, and I said, ‘Linda, do you know anything about The Exorcist?’” Friedkin recalled. “She said, ‘Yeah, I read the book. It’s about a little girl who gets possessed by the devil and then does a whole bunch of bad things.’

“I said, ‘Like what? What kind of things does she do?’” he said, testing her.

She told him: “‘Well, she hits her mother across her face. And she pushes a man out her bedroom window. And she masturbates with a crucifix.’”

This was the moment in the story that caused more angst than any other, and remains a deeply controversial part of the movie (even though the scene is shot from behind, so a stand-in could be used.)

“I look over and her mother is smiling,” Friedkin says. “I asked, ‘Do you know what that means?’ She said, ‘Yes, it’s like jerking off, isn’t it?’”

When the director took a deep breath and asked if she even knew what that meant, she replied: “’Sure. Don’t you?’”

“She was the only one of all the young girls I felt would not be destroyed by this experience,” Friedkin says.

Still, he says, he tried to keep the set light and jokey during her most intense scenes, to alleviate any residual weirdness for her.

“If she was bothered by it during production, the rest of the cast couldn’t function and nor could the crew,” he said. “In the dailies, you’d see after every take, where she’s saying the most horrific things, I’d say cut, and then one of the prop men would hand her a milkshake and she’d be laughing. The whole thing to her was a game.”

5.) Carving out the self-mutilated face

You’ve probably seen that internet prank, where a friend tells you to do a complicated, but seemingly innocuous maze – and just when it demands the most concentration, a shrieking, nightmarish face appears.

Usually, it’s a smiling shot of Linda Blair in demon make-up from The Exorcist.

Even four decades later, that look gives new definition to the phrase “hard on the eyes.”

You can thank Dick Smith, a legendary make-up man who received an honorary Oscar last year, for that contribution to America’s high blood pressure.

Instead of going for a straight monster look, he and Friedkin decided, “Why don’t we try to do what looks like she scarred herself and these sores will get worse and worse?” the director said. “[Smith] did a lot of research on gangrenous wounds and burn victims. And he brought me a lot of actual photos of people to whom that had happened.”

It’s ugly work, but someone had to do it.

6.) Another changing face on The Exorcist

If you didn’t know about Smith’s expert make-up skills, you’d be forgiven for thinking: Max von Sydow has held up really well over the past 40 years!

Or, the flip-side: Max von Sydow looks like he has always been in his 80s!

The truth is, the Swedish actor was only 43 when he made The Exorcist, but was aged to look much older. Friedkin says they chose him for the role not just because he was a great performer, but because “he looked like Father Bowdern,” the real-life priest who performed the 1949 exorcism.

“His make up took four hours a day,” says Friedkin. For the opening scenes at a desert archaeology dig – which were shot in Mosul, Iraq – the heat soared above 120 degrees, which made the process all the more brutal for the actor.

“When we finished they would peel it off and the sweat would just pour out of his face,” Friedkin says.

It’s not quite as bad as the Nazi faces melting at the end of Raiders of the Lost Ark, but it probably made von Sydow’s head feel like one swollen, swimming blister all day long.

7.) A voice actress, possessed by real personal demons

Aside from Blair’s sickening make-up, the other key terrifying part of the character is its demon voice.

Compare the before and after above, as Blair’s voice is replaced by something growling, reedy, and sinister.

The final demon voice was created without any significant post-production alteration by an Academy Award-winning actress who went to dangerous lengths to create it.

“I had a lot of trouble devising how the demon would sound,” Friedkin said. “If you read the novel, it says ‘The voice was terrible’ or ‘It was frightening’ … But how do you achieve that?”

He came up with the notion that the voice should be gender neutral, neither male nor female.

“I remembered from dramatic radio, this great actress Mercedes McCambridge, who worked a lot with Orson Welles and the great radio performers. I remembered she had a kind of neutral sound,” the director recalled. He tracked her down to a stage production of Who’s Afraid of Virginia Woolf in Dallas, and got her to come see a rough cut of the film.

“Afterward, she said: ‘Do you know anything about me? What do you know about me?’” he recalled. “I said, ‘Only that you’re a really great actress and I remember your voice from 25, 30 years ago.’

“She said, ‘Well … I’m a practicing Catholic,’ she said, ‘And I am also a drunk. I went through AA, and I’ve had many deep psychological problems, and the church has been like a rock for me.’”

It seemed like she was getting ready to turn down the project, but instead told him: “’I know what you want me to do for this voice.’”

Then she added: “’If I do that … I’m going to start drinking again.’”

8.) Getting drunk wasn’t her fear — it was her requirement

McCambridge, who died in 2004, told Friedkin she would need to swallow raw eggs to make her voice mucusy, start smoking cigarettes again, and also guzzle booze to get the languid, throaty croak necessary for the demon.

Since she was falling off the wagon to do the job, she had one other request: “She said, ‘I’m going to want these two priest friends of mine to be with me in the soundstage at all times,’” Friedkin recalls, still with an element of disbelief. “So I agreed to all of that.”

McCambridge also performed most of the role while strapped to a chair, since that’s how the character was positioned in the movie — even though she later gave interviews saying that didn’t seem necessary to her.

“I tied her hands behind her back. And she would do the dubbing a line at a time, and often she would ask for more booze and more cigarettes,’” the director said. “What would happen to her voice is you sometimes hear a wheezing sound in addition to the words. That came out of her throat.

“You’ve experienced that when you’ve had a cold, and you have a sore throat and with the cough medicine, your throat will make several different pitches at the same time. That’s what happened with her.”

It was a brutal experience for McCambridge, however. “She’d come off a take and then go to a couch in the back where these two priests were and she would collapse in their arms and burst into tears,” Friedkin said.

Playing the demon pulled up some long-buried ones within herself.

9.) Does Friedkin think the set was cursed?

Ellen Burstyn wrenched her back. Max von Sydow’s brother died on the actor’s first day of shooting. And Jason Miller’s young son, Jordan, was struck and nearly killed by a man on a motorbike. (He later recovered fully.) The film was also the last role for actor Jack MacGowran, who played the alcoholic filmmaker who meets a bad end. (He finished the role, but died from the flu before the movie was released.)

Though it all happened during the making of The Exorcist, Friedkin dismisses any notion the set was actually haunted. Instead, awful things that might have happened during the making of any movie took on a superstitious significance because of the subject matter of this one.

“There were only a couple strange things, out of the ordinary,” the director claims. “One day at 4 in the morning, I got a call from a production manager and he said ‘Don’t bother coming to work this morning. The set is burning to the ground right now as we speak.’”

The set, which was the interior of the home where Regan and her mother lived, was located in an old New York soundstage. Though the reason for the fire was never certain, Friedkin believes the cause had claws, wings, and a foul odor…

“It was an old building. There were pigeons flying around up there, and the theory [the insurance company] paid off on was that one of the pigeons flew into a light box,” Friedkin said.

Production was shut down for two months. A costly delay, although hardly the worst the devil has ever done.

10.) Unsettling subliminal messages buried within

It’s hardly a secret that Friedkin used subliminal imagery in the film to unsettle viewers, though he likes to say there are a lot of “bulls—t theories” out there.

The truth is, he used the sound of bees in some early sequences, which triggers an innate fear response in most people. You don’t know why you’re uncomfortable, but fight-or-flight is telling you something dangerous is near.

The buzzing of bees is a primal fear, but Friedkin said he also layered in “disturbing industrial sounds” in the background of the demon scenes, which also create a subconscious desire to back away from danger.

The most notable subliminal trick is the “white face” that flashes for just a fraction of a second during Fr. Karras’ dream sequence about his deceased mother. That face, pictured above, was never meant to be fully detected by the audience. “You couldn’t catch it before VHS,” Friedkin laments. “And now you can stop the DVD and stare at it.”

The face is that of Linda Blair’s stand-in, and the make-up was Dick Smith’s first proposal for the little girl’s demon appearance, before they settled on the mutilation motif. “She had all white face and red lips,” Friedkin said. “I didn’t like the make-up for the demon, but viewed as a quick cut, it’s very frightening.”

As for other images people purport to see in the film …? Friedkin says that’s just power of imagination.