Carbon Costume

In Clue, Mr. Green (Michael McKean) is a State Department employee and guest of Mr. Boddy. He is blackmailed for being gay, a secret which would cost him his job. In one of the endings, he is suspected of killing the singing telegram girl in the hall with the revolver. He ultimately reveals himself as an undercover FBI agent, who actually killed Mr. Boddy in the hall with the revolver.