Inspector Morse: Death Is Now My Neighbour (1997)

Rachel James is shot through her kitchen window while having breakfast early one morning. She was having an affair with Dr. Julian Storrs, an Oxford professor who is a candidate for Master of Lonsdale College. When her next door neighbor is also killed however, Morse determines that the shooting of James may have been in error. Morse also suspects that he may have been a blackmailer. Both Storrs an his rival for the Masters position, Denis Cornford had secrets that would make them suspects. Morse determines that several others also had things to hide and any one of them could have committed the murders.