The Exorcist was one of the first "event" movies, inspiring countless debates, magazine articles, and news stories about people fainting in the theatres.

According to author Mark Kermode in his book The Exorcist, the film was praised by segments of the Catholic church for its profound spirituality and branded satanic by the Reverend Billy Graham. He writes "for the first time in a mainstream movie, audiences witnessed the graphic desecration of everything that was considered wholesome and good about the fading American dream - the home, the family, the church, and most shockingly, the child."

Movies such as Rosemary's Baby had touched upon ideas like this, but nothing had ever come close to matching the graphic visual onslaught in The Exorcist.

Director William Friedkin, who had won an Academy Award for his work on The French Connection, calls The Exorcist a film about "the mystery of faith" and believes the movie makes people question their own value system and even their sanity. He says the movie has endured all these years because it "strongly and realistically tries to make the case for spiritual forces in the universe, both good and evil."

Novelist Blatty based his story on an article he had read about real life events which occured in 1949. He was a junior at the Jesuitical Georgetown University, when he first came across the piece about a little boy who had been possessed and undergone an exorcism.

The movie begins in Northern Iraq, where an extensive excavation is taking place. Among the arrowheads and coins, Father Lancaster Merrin (Max Von Sydow) finds a unique piece with some kind of demonic face on it. He appears to grow weak and heads out to an isolated area of the site, where he is mesmerized by a statue that resembles his discovery.

Chris MacNeil (Ellen Burstyn) is a successful actress who is living in Georgetown while she films a new movie. One evening while relaxing in her room, she hears a noise coming from the attic. She checks up on her daughter Regan (Linda Blair) who is fast asleep. The next morning, she tells her servants she is convinced there must be rats in the townhouse.

Her current script calls for her to play a college professor. The director is Burke Dennings (Jack MacGowran), an old friend of hers. During the filming of one scene...a local priest named Father Damien Karras (Jason Miller) watches from the sidelines.

After the shoot, Chris walks home in the brisk autumn weather...watching as a group of kids enjoy their Halloween. As she passes by a church, she catches part of an intense conversation between Father Karras and a younger priest.

When she arrives home, her secretary Sharon (Kitty Winn) gives her an invitation to an upcoming function at the White House. Regan, who is obviously very close to her mother, greets her.

Father Karras take a trip to New York to visit his elderly mother (played by Vasiliki Maliaros). She lives in an old tenement building in a run-down section of the city.

Mrs. Karras is happy to see her son but resists his wish that she move out. "I'm not going no place," she tells him in a thick Greek accent. The old woman senses that something is on his mind but he assures her that everything is fine.

Meanwhile, Chris is in her basement with Regan and sees a Ouija Board. The girl found it in the closet when they moved in and she tells her mother that an imaginary friend named "Captain Howdy" usually answers her questions.

Chris puts Regan to bed and tells her she wants to take her sightseeing for her birthday. Her daughter is convinced that she has a thing for Burke because he's always around. Chris tells her they're just good friends and that she still loves Regan's father.

Father Karras goes back to Georgetown, where he meets a fellow priest at a bar. He's sad about his mother and says he regrets leaving her by herself in New York. He talks about wanting to be reassigned (Karras is a psychiatrist) because he feels he "can't cut it anymore." He also calls himself unfit and says he believes he's lost his faith.

Regan's birthday arrives and Chris is furious that her estranged husband hasn't even called his daughter. She tries to phone him in Rome but can't reach him. Regan hears her mother yelling and cursing at the operator. She spends the night in Chris's bed.

In the morning, Chris gets a call telling her to get to the set. When she asks the girl why she didn't sleep in her own bed, Regan tells her the "bed was shaking."

Hearing a rattling sound from the attic again, Chris lights a candle and goes up to investigate. There are no rats to be found, as Karl (Rudolf Shundler) - one of her housekeepers, points out to her.

At the local parish, something strange is going on. A priest finds a statue of the Virgin Mary in the chapel grotesquely desecrated.

Father Karras rushes back to New York to visit his mother who is now ill and in a hospital. His uncle (played by Titos Vandis) tells him an edema has affected the elderly woman's brain. The priest is shocked to find his mother is actually in the psychiatric ward. "Why did you do this to me, Dimmie?" she tearfully asks. Her brother tells Karras he couldn't afford to put her in a private hospital.

Shortly after, Chris throws a lavish party in her home. Everyone is having a great time, especially Burke. He's drunk and gets into a fight with one of the guests, whom he accuses of being a Nazi. One of the people invited is Father Dyer (Reverend William O'Malley). Chris asks him about Father Karras and is told that the priest is going through a rough time because his mother died the night before.

Chris takes a break from the party to check up on Regan, who appears to be sleeping. When she leaves the girl's room, Regan opens her eyes.

The night winds down and Sharon and Chris help Burke (who can hardly stand up) to the door. The remaining guests gather around the piano, where Father Dyer entertains them with his playing. Suddenly, Regan appears and says "You're gonna die up there," before urinating on the carpet.

Chris is embarrased and brushes it off by saying the girl has been sick. She takes Regan upstairs and gives her a bath. Her friends have left and she puts the girl to bed again, while her maid Willi (Gina Petrushka) tries to get the stains out of the rug.

All of a sudden, Chris hears Regan's screams coming from her room. She finds her daughter's bed shaking violently. "Make it stop!" the little girl cries out.

Father Dyer pays Father Karras a visit and finds him plagued with guilt over his mother's death. He brings over a bottle of liquor to help his friend ease the pain and tells him there was nothing he could do.

The depressed priest falls asleep and has a dream about his mother. In it, she calls out for him and then descends into a subway station before he can reach her. (There's also a quick and eerie image of a demonic face.)

Chris believes her daughter's problem is a medical one and takes her to the Barringer Clinic. The girl does not want to be injected for a test and struggles to break free. She spits at Dr. Klein (Barton Heyman) and calls him a "fucking bastard." That day, Chris gets a prognosis.

The doctor tells her Regan has symptoms "of a type of disturbance in the chemical-electrical activity of the brain." He believes it's a lesion on her temporal lobe and tells Chris it's rare but does cause "bizarre hallucinations."

Dr. Klein blames the shaking of the bed on convulsions due to muscular spasms. Chris doesn't buy it, saying that she got on the bed herself and that the whole bed was thumping and rising off the floor.

She wants to know what is causing her daughter's personality to change and is told it's common to find destructive and even criminal behavior with this kind of condition. More tests follow as Regan is subjected to a series of gruelling examinations. When the x-rays come back, Dr. Klein and Dr. Taney (Robert Symonds) find nothing unusual in her brain.

Chris frantically calls the clinic. Both doctors rush over to the house where Sharon tells them they've already given Regan her medication. They find the girl shaking on the bed, her eyes rolled back into her head. When Dr. Klein approaches her, she knocks him to the floor.

"Keep away! The sow is mine!" she screams in a horrifyingly deep voice. Chris can hardly bear it anymore, especially when the little girl yells out "fuck me, fuck me" to the doctors. They're finally able to sedate her.

Dr. Taney and Dr. Klein still believe the problem is medical, rejecting Chris's theory of a spit personality. They say they're going to give the girl another spinal to find anything they missed the first time. The tests come back and they're normal. Finally, Dr. Klein says they should start looking for a shrink.

Chris drives home and notices a commotion at the bottom of a long narrow staircase near her townhouse. Inside, the lights are flickering. Sharon, who was supposed to be watching Regan, is nowhere to be found. Regan is in bed asleep and her room is freezing cold. The windows are wide open.

Sharon returns and tells Chris she went out to get some Thorazine for Regan. She says she left Burke to watch the girl. The doorbell rings. It's Chuck (Ron Faber) the assistant director, with some bad news. Burke was found dead with a broken neck, at the bottom of the stairs just outside.

Regan is put under hynosis by a psychiatrist (played by Arthur Storch). The unnaturally pale girl emits a horrible stench from her mouth and attacks the shrink by grabbing his crotch.

Lt. William F. Kinderman (Lee J. Cobb), who's investigating Burke's death, meets up with Father Karras. He asks the priest what he knows about witchcraft. Karras says he once did a paper on the subject from the psychiatric end.

Lt. Kinderman then asks about the desecration in the church and tells Karras that Burke was found with his head turned completely around, facing backwards. He believes there is some connection between the two events and that witchcraft is involved. Perhaps a sick priest? Karras says he doesn't know anyone that fits the description.

Back at the clinic, the doctors and nurses have given up. Dr. Klein tells Chris that Regan's behavior is rarely ever seen anymore except in primitive cultures.

Chris is firm about not putting her daughter away. Finally, she's asked if she or her daughter have any religious beliefs; she answers no.

The doctors inform Chris that the only option remaining is an exorcism, which only Catholics really practice anymore. Of course, Dr. Klein tells her, it's "only the power of suggestion."

While looking for clues at the bottom of the staircase where Burke was found, Lt. Kinderman finds something peculiar. (It looks like the piece Father Merrin picked up in Iraq.) He stops by Chris's home just as she's trying to find out which member of her staff put a cross under Regan's pillow.

Kinderman asks her if the girl remembers Burke being in her room the night he died. His theory is that the director was killed by a man and then pushed from Regan's window. Before he leaves, he asks the actress for her autograph.

A scream comes from Regan's room. Chris runs up and opens the door to find everything in the room flying around. What's worse, the girl (in the most infamous scene in horror history) is masturbating with a crucifix.

When Chris tries to stop her, Regan shoves her mother's head in her bloodied crotch and smacks her across the room...spewing obscenities the entire time. Sharon tries to intervene but Regan causes the door to shut. And then...Regan's head turns 180 degrees and she tells her mother (in Burke's voice) "Do you know what she did, your cunting daughter?"

Realizing the extraordinary circumstances, Chris arranges to meet with Father Karras. Wearing sunglasses and with her face bruised, she asks how she can go about getting an exorcism for her daughter. Karras tells her it's been an outdated idea since we learned about "mental illness, paranoia, schizophrenia" and all the things they taught him at Harvard. Chris says she truly thinks her little girl is possessed.

They go back to the house, where Father Karras sees for himself. Regan is strapped to the bed and looks like anything but a sweet young girl. Several voices come out of her, including one who claims to be the devil. The "devil" says that Father Karras' mother is inside the girl's body as well.

When the priest asks what her maiden name is, Regan projectile vomits on him. Chris is kind enough to wash his sweater. Despite this, Karras recommends the girl stay in a hospital under observation for six months. As he's leaving, he asks Chris if there's any way Regan could know that his mother died recently. The answer is no.

After his next mass, Karras decides to see Regan again. Her condition is worsening. The voice in Regan tells him "what an excellent day for an exorcism." The girl also begins to speak in Latin and other languages, while Karras records her.

She writhes in pain when he throws what he calls "holy water" on her. It was just tap water he tells Chris, which doesn't support the case for an exorcism. The priest is then shocked to hear the girl's mother say that Regan murdered Burke Dennings.

Father Karras takes the recordings to a professional who tells him Regan was speaking English backwards. He listens to the tape alone later that night and hears phrases like "fight the priest" and "I am no one" repeated over and over. The name "Merrin" is also clearly audible.

A call comes in from Sharon telling him to come to the townhouse right away. He rushes over and Regan's room is freezing cold. Sharon shows him the reason for his visit - she lifts the girl's shirt up and the words "help me" are visible on her stomach.

Karras realizes the child's condition meets the requirements for the exorcism. Arrangements are made to have Father Merrin conduct the ritual. Merrin is the logical choice because he had been involved in an exorcism in Africa some years before.

Despite some misgivings about his age, the priest is notified in Woodstock, New York and he heads for Georgetown. He arrives at the house on a misty, foggy night. (Surely one of the most iconic images in film history.)

Father Karras is already inside and Merrin sends him back to the residence to gather up some things: a cassock, a purple stole, holy water and Karras' copy of The Roman Ritual.

Before they begin, the younger priest tries to give some background on the case. He says Regan has manifested at least three personalities, to which Father Merrin says "there is only one." Merrin also tells him the demon will lie...but will mix truth with those lies.

Among the gems the demon says to Merrin when it first sees him is the classic: "stick your cock up her ass, you mother-fucking worthless cock sucker!"

The two priests pray as the girl curses, emits various sounds and voices - and spits on Father Karras. She rips a chain off Merrin and the bed begins to shake violently...as she tries to get loose from the straps.

Karras and Merrin remain calm under the circumstances although Karras almost loses his cool when the demon tells him he killed his mother and left her alone to die.

Finally breaking free and with only the whites of her eyes visible, Regan levitates off the bed. The priests bring her back down by repeating the line "the power of Christ compels you" over and over.

The men take a break and Father Merrin goes into the bathroom to take a pill for his heart condition.

Karras goes back into the bedroom to check the girl's heart and hears his mother's voice come out of Regan. "You're not my mother!" he screams. Merrin tells him to leave so he can finish the exorcism by himself.

Chris finds Karras sitting at the bottom of the stairs and asks if her daughter is going to die. "No" he says before going back up to Regan's room. The doorbell rings and it's Lt. Kinderman.

Karras finds Father Merrin slumped over on the bed, apparently dead of a heart attack. He tries to save him but it is too late. Regan is sitting on the bed giggling and the priest attacks her. He strangles her and yells "take me!"

The demon does indeed enter his body and Karras leaps out of the window and down the long flight of stairs. Chris and Lt. Kinderman find the little girl crying in the corner of the room. The police arrive and Father Dyer gives the dying Karras the final rites of absolution.

Soon after, Chris prepares to move out of the house with her daughter. She says goodbye to Sharon, who has decided not to go with her. The secretary gives her the chain which she found in Regan's bedroom. Father Dyer is there to wish them well. Chris tells him the girl doesn't remember any of it.

Regan is healthy again - although bruised and battered from the harrowing experience. Chris promises to keep in touch with Father Dyer. Regan notices the priest's white collar and plants a kiss on his cheek. Before they drive off, Chris gives Father Karras' chain to Dyer as a gift.

The Exorcist received a whopping 10 Academy Award nominations, including nods for Best Picture and Director.

Both Linda Blair and Jason Miller were nominated for their film debuts. (It's been said the revelation that Mercedes McCambridge dubbed much of the demon's voice ruined Blair's chance of taking home the Oscar.) In the end, the movie won just two, for Best Adapted Screenplay and Best Sound.

What it didn't win as far as major awards, it surely made up for at the box-office. The movie would go on to be the biggest hit for Warner Brothers, and second only to The Godfather as the all-time money grossing champ.

William Friedkin did a masterful job of transforming William Peter Blatty's book into a motion picture. He based the character of Chris MacNeil partially on his good friend Shirley MacLaine and even offered her the role. She declined, having already made The Possession of Joel Delaney the year before, a film with a similar plot.

Friedkin directed the cast of well-knowns and newcomers with astonishing flair. All the performances are outstanding. Burstyn is particularly excellent and moving as she tries to comprehend what is happening to her innocent daughter.

Everything about The Exorcist was top-notch, from the direction, to the acting, to the fantastic make-up by Dick Smith, to Owen Roizman's stunning cinematography.

The music by Jack Nitzsche is especially memorable - and the Tubular Bells theme written by Mike Oldfield - would become one of the most famous and imitated pieces of music ever featured in a film score.

The Exorcist, along with Brian De Palma's Carrie, features some of the most poignant sequences ever captured in the genre. In many ways, the film is about Father Karras' lapse of faith, as well as the little girl's plight.

Scenes of the priest with his mother, and his death at the end, tug at the heartstrings and bring a truly human element to the supernatural goings on.

At its essence, the classic story of good versus evil, this theme doesn't seem to have much power nowadays in movies. Everything's morally too blurry now, too cheap. But this film is powerful, incredibly scary, and like a ghost, it will haunt your mind for years to come.