'The Exorcist' writer William Peter Blatty returns to direct this sequel to the original film based on his own novel. 15 years have passed since Father Damien Karras (Jason Miller) died exorcising Regan MacNeil. Now his best friend Lt. Kinderman (George C. Scott) is troubled by a series of mysterious murders which are strangely reminiscent of those committed by the Gemini killer - who was executed on the night Karras died. Does the killer's spirit live on, and if so in whom? Kinderman's investigation leads him to an amnesiac in a mental hospital who has recently awoken from a coma, can describe the Gemini killings in detail and bears an uncanny resemblance to Damien Karras.