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"The Exorcist III" is notable as the only installment in the "Exorcist" franchise to be penned and helmed by original novelist William Peter Blatty. Unlike its predecessors, "The Exorcist III" doesn't directly center on the possessed Regan MacNeil but introduces Lieutenant Kinderman, investigating a series of gruesome serial murders potentially connected to the deceased serial killer Gemini, whose presence still lingers, setting the stage for unsettling events in Georgetown.