William Peter Blatty, who wrote the original novel &NFi;The Exorcist&NFi_; and the Oscar-winning screenplay, writes and directs Part 3, which is based on his novel &NFi;Legion.&NFi_; When a supernatural serial killer strikes again, police detective Bill Kinderman (George C. Scott, taking over Lee J. Cobb's role from the first film) investigates. The original's Father Damien, Jason Miller, returns in a guest role.