Unfaithfully Yours (1984) on Netflix

Claude Eastman, is a composer and conductor. He is married to Daniella, who is half his age. While away on a trip he told his Italian driver, Giuseppe, to tell his friend Norman to keep an eye on her, or take care of her. But his english is not too good, so Norman thought he was saying that Claude wanted him to hire a private eye to keep tabs on her. Which he did. Claude tells him that it's ok but the man Norman hired gives him his report and it says something happened while he was away. Claude, of course, tells him to throw it away but after Norman leaves, Claude tries to retrieve it and tries to read it but Daniella's there, when Giuseppe destoys it, he goes to the man Norman hired to get a copy. He tells Claude that a man went into his apartment while he was away and left at an unusual hour, and that he also has a video. Claude tells him to destroy it but shortly after leaving returns so that he can watch it. Now the video's a little fuzzy but clearly he can see that the man wears a particular type of clothing. Claude goes around checking every man he knows to see if they wear that clothing. He discovers that Max, his protege and a ladies man wears it. After confronting Daniella, she is harboring a secret but not what Claude thinks it is, so when she tells Claude that it's no big thing, Claude freaks out, and is planning to kill her and frame Max but an unforeseen circumstance disrupts the perfect plan he dreamed up.