Legion by William Peter Blatty

The sequel to The Exorcist, A young boy is found horribly murdered in a mock crucifixion, multiple priests found beheaded and exsanguinated; Is the murderer the elderly woman who witnessed the crime? A neurologist who can no longer bear the pain life inflicts on its victims? A psychiatrist with a macabre sense of humor and a guilty secret? A mysterious mental patient, locked in silent isolation?

Lieutenant Kinderman follows a bewildering trail that links all these people, confronting a new enigma at every turn even as more murders surface. Why does each victim suffer the same dreadful mutilations? Why are two of the victims priests? Is there a connection between these crimes and another series of murders that took place 12 years ago – and supposedly ended with the death of the killer?