Sherlock Holmes and the Masks of Death (1984)

Sherlock Holmes has retired. But when MacDonald asks him to take on another case, he says yes. There have been some mysterious murders, and there are no visible causes for the deaths. At the same time Holmes gets this case, Graf Udo Von Felseck gives him another case: find a young and missing prince to prevent war between Germany and England. But Von Felseck is not as honest as he seems...