Black Mass is a crime drama film based on the true story of notorious Boston gangster, James 'Whitey' Bulger. Benedict Cumberbatch plays the role of Billy Bulger, the younger brother of Whitey Bulger and a powerful politician in Massachusetts. The film explores the complex relationship between the two brothers and the extent of Whitey Bulger's criminal activities. Cumberbatch delivers a compelling performance as Billy Bulger, showcasing his versatility as an actor. Black Mass is a gripping and intense film that delves into the dark underbelly of organized crime.