Many Americans felt lost in the 1970s, and one movie spoke to disillusioned times. Opening on Dec. 26, 1973—one day after Christmas—Warner Bros. released The Exorcist as “the scariest movie of all time.” The film brought to life the spirit of the devil within the body of a child, complete with projectile vomiting, levitation, blasphemous curses and head-spinning. It would go on to become a box-office sensation and a cultural phenomenon, and along the way it made Catholic priests into action heroes and teenage girls into feared forces. Fifty years on, admiration and fear of the film remains. It has been copied, stolen from, spoofed and analyzed. The devil may be in the details, but when it comes to The Exorcist, it’s all about the devil—and how the demon emerged as a true and unlikely movie star all across America.