Inspector Morse: Deceived by Flight (1989)

Morse and Lewis investigate the death of Anthony Donn who is attending an old boys cricket match at his Oxford college in advance of the team going on a European tour. Morse knew him and had actually met him again not long before his death. The death looks like a suicide, but Morse has his doubts. So does his wife Kate, who is surprised to learn that her husband carried a loaded gun. Lewis goes undercover and joins the cricket team. He learns there is at least one couple, the Fosters, staying at the college who may not be who they claim to be. When a second murder occurs at the cricket grounds, Morse learns the true nature of the Fosters stay at the college and begins to unravel the mystery.