12-year-old Regan MacNeil begins to adapt an explicit new personality as strange events befall the local area of Georgetown. Her mother becomes torn between science and superstition in a desperate bid to save her daughter, and ultimately turns to her last hope: Father Damien Karras, a troubled priest who is struggling with his own faith.

An alcoholic American couple travel to the UK with their son so he can meet his grandmother but they walk in on their crazed uncle who is in the midst of reviving a centuries-old Druid witch.

Set fifteen years after the original film, The Exorcist III centers around the philosophical Lieutenant William F. Kinderman who is investigating a baffling series of murders around Georgetown that all contain the hallmarks of The Gemini, a deceased serial killer. It eventually leads him to a catatonic patient in a psychiatric hospital who has recently started to speak, claiming he is the The Gemini and detailing the murders, but bears a striking resemblance to Father Damien Karras.

Col. Vincent Kane is a military psychiatrist who takes charge of an army mental hospital situated in a secluded castle. Among Kane’s many eccentric patients is Capt. Billy Cutshaw, a troubled astronaut in the midst of an existential crisis. Although Kane’s own grasp on sanity is questionable, he manages to engage Cutshaw in a series of thoughtful conversations about science and faith that deeply affect the lives of both men.

Patty McCormack’s “Mommy” is psychotically obsessed with her 12-year-old daughter Jessica Ann — so much so that when she finds out Jessica didn’t get the “Student of the Year” award again, she solves the problem by murdering the teacher who didn’t recommend her for it. She dismisses the killing as inconsequential (“a minor accident”), but the homicide detective assigned to the case suspects her immediately, and an insurance investigator who also suspects her tries to get close to Jessica Ann to find out what really happened.