Here's a breakdown of the plot:
* Regan's Possession: The film begins with Regan, a seemingly normal and cheerful girl, exhibiting disturbing and increasingly violent behavior. She starts showing signs of supernatural abilities and undergoes a physical transformation, becoming increasingly demonic in her appearance and actions.
* Seeking Help: Her mother, Chris MacNeil, a famous actress, seeks medical help but finds no explanation for Regan's condition. Desperate, she turns to Father Damien Karras, a Jesuit priest and psychiatrist, who suspects demonic possession.
* The Exorcism: Father Karras brings in Father Lankester Merrin, an experienced exorcist, to help. The two priests, along with Chris, face a terrifying battle against the demon, Pazuzu, who has possessed Regan.
* The Fight: The exorcism is a brutal and harrowing ordeal, filled with shocking and graphic imagery, where the priests confront the demon's powerful presence.
* Sacrifice and Resolution: The battle culminates in a climactic confrontation, leading to a tragic sacrifice and a resolution that leaves the audience pondering the nature of faith, good vs. evil, and the power of demonic forces.
The Exorcist is a landmark film in horror cinema known for its disturbing themes, graphic content, and psychological impact. It explores the boundaries of faith, the struggle against demonic possession, and the psychological trauma of the characters involved.