Inspector Morse: The Last Enemy (1989)

When a decapitated body is found in the canal, the police must first identify the victim. The Master of an Oxford college, Sir Alexander Reece, contacts his old friend Morse to obtain assistance in locating the Deputy Master, David Kerridge, who is now four days overdue from his planned return to college. Kerridge is found battered to death in his London flat but oddly, it's also determined that the body in the canal was wearing one of Kerridge's suits. Morse and Lewis conclude that the headless body is that of Nicholas Balarat, a member of Reece's college and a senior civil servant who may have denied Reece an important appointment. However, another murder at the college sends the detectives in an altogether different direction.