In 'The Exorcist' (1973), a 12-year-old girl named Regan begins exhibiting strange, inexplicable behavior. Her mother, desperate to find her child's cure, turns to a local priest for help, leading to a terrifying, life-threatening exorcism.
Friedkin shot demonic possession like a police procedural — clinical, documentary-real — and that refusal to stylize is exactly what made audiences faint in the aisles. It reset the ceiling for what mainstream horror could get away with.