Black Mass is a 2015 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 prominent politician. The movie delves into the complex relationship between the two brothers and the web of corruption and violence that surrounds them. With its gritty atmosphere and intense performances, Black Mass offers a gripping portrayal of organized crime and its impact on individuals and society.