The exorcist - William Peter Blatty

Georgetown, Washington D.C., 1973.
Actress and divorced mother Chris MacNeil starts to experience 'difficulties' with her usually sweet-natured eleven-year-old daughter Regan.
The child becomes afflicted by spasms, convulsions and unsettling amnesiac episodes; these abruptly worsen into violent fits of appalling foul-mouthed curses, accompanied by physical mutation.
Medical science is baffled by Regan's plight and, in her increasing despair, Chris turns to troubled priest and psychiatrist Damien Karras, who immediately recognises something profoundly malevolent in Regan's distorted fetures and speech.
On Karras's recommendation, the Church summons Father Merrin, a specialist in the exorcism of demons . . .

William Peter Blatty scripted this version of his own best-selling novel for director William Friedkin, and was rewarded with an Oscar for Best Adapted Screenplay of 1973.
This publication also includes the texts of the film's legendary 'lost scenes' and excised dialogue which shed additional light on The Exorcist's profound darkness.