Wicked Games (movie, 1994)

Detective Gary discovers that his wife is having an affair. Despondent, he drinks and discusses his problem with friend Dan, a police detective. When someone in a copper mask begins slaughtering people connected to Gary's life, Dan begins suspecting Gary, whose cousin Mike had a similar slip of the gears. Dan discusses the case with eminent psychiatrist Dr. Siedow, who has a few sexually slipped gears of his own. Together they try to stop the fiend before more people are killed.