Black Mass is a crime drama film based on the true story of James 'Whitey' Bulger, a notorious Boston gangster. Benedict Cumberbatch portrays Billy Bulger, Whitey's younger brother and a powerful politician. The film delves into the complex dynamics between the brothers and their involvement in organized crime. Cumberbatch delivers a compelling performance, showcasing the conflicting loyalties and moral dilemmas faced by his character. Black Mass is a gripping and gritty film that explores the dark underbelly of the criminal world.