Black Mass is a crime drama film based on the true story of notorious Boston gangster Whitey Bulger. Benedict Cumberbatch plays the role of Billy Bulger, Whitey's younger brother and a powerful politician. The film follows the rise and fall of Whitey Bulger's criminal empire and the complex relationship between the two brothers. With its gritty atmosphere, intense performances, and gripping storyline, Black Mass offers a compelling portrayal of organized crime and the blurred lines between loyalty and betrayal.