Poirot: The Adventure of the Italian Nobleman (1993)

Poirot and his friend Captain Hastings find themselves investigating the murder of Count Foscatini, who was found in his flat. As it turns out, the dead man's valet, Mr. Graves, has been dating Miss Lemon and has been less than honest with her about his profession. As for the dead nobleman, the police believe he was being blackmailed. The Italian Embassy denies any knowledge of the man and denies that he had any official role in the country. Poirot doubts the veracity of their claims but also concludes that others are lying as well.