Villian(s)  Demon possession

Actor(s):  George C. Scott, Ed Flanders, Jason Miller, Scott Wilson

Brief Description  The Exorcist III (1990) is a supernatural psychological horror film written and directed by William Peter Blatty. Adapted from his own 1983 novel Legion, it functions as a direct sequel to the 1973 classic The Exorcist, completely ignoring the events of Exorcist II: The Heretic. Blatty initially intended to name the film Legion, but Morgan Creek Productions mandated the title change and forced late-stage reshoots to add a heavy special-effects exorcism climax.

Plot:
Set 15 years after the death of Father Damien Karras, the story follows his grieving best friend, Police Lieutenant William F. Kinderman. Kinderman is investigating a string of gruesome, ritualistic murders in Georgetown. The killings feature a specific, horrifying calling card: the victims are decapitated and desecrated with religious iconography. The Modus Operandi exactly mirrors the Gemini Killer, a notorious serial killer executed on the exact night Father Karras died. The details of the new crimes are classified information, meaning a copycat is highly unlikely. Kinderman’s investigation leads him to a high-security psychiatric hospital managed by Dr. Temple. He finds an amnesiac, catatonic inmate locked in "Cell 11" who has recently awakened. The patient looks uncannily like the deceased Father Damien Karras. When he speaks, his personality shifts violently. He boasts that he is the soul of the executed Gemini Killer. The entity explains that after Father Karras jumped out of the window to destroy the demon Pazuzu in the original film, the vengeful demon intercepted Karras's departing soul.

As punishment, the demon forced the soul of the Gemini Killer into Karras’s dying, brain-damaged body. Because Karras's body is physically broken, the Gemini entity cannot leave the cell freely. Instead, it uses demonic forces to invade the minds of elderly dementia and catatonic patients in the ward, using them as mindless vessels to sneak out and execute the new murders. After the Gemini entity targets Kinderman's inner circle—brutally murdering his close friend Father Dyer—a veteran priest named Father Morning arrives at the hospital to perform a frantic, intense exorcism. Father Morning is overwhelmed and savagely attacked by the entity. During the chaos, Father Karras briefly breaks through the Gemini entity's control, regaining his free will for a final moment. He begs a compromised, weeping Kinderman to shoot him. Kinderman fires multiple shots, killing Karras, freeing his soul, and permanently putting an end to the Gemini Killer's reign of terror.