Sherlock (TV Series) - Season 1 - Episode 1: "A Study in Pink"

In this modern retelling, Dr. John Watson, a war veteran, becomes flatmates with the brilliant but eccentric detective Sherlock Holmes. Together, they investigate a series of apparent suicides linked to a mysterious cab driver. As they unravel clues, they confront a deadly game involving poisoned pills, leading to a shocking revelation about the identity of the killer: Moriarty.