Cannon was portrayed in the series as a veteran of the Korean War and a former member of the Los Angeles Police Department. He was street smart but also appeared to have an unusually high level of education outside the law enforcement field. Besides his familiarity with several languages, he showed extensive knowledge of such diverse subjects as science, art and history. Cannon was a widower, having lost his wife and son in a bomb attack while he was on the police force, as revealed in the two-hour pilot.