James Whitey Bulger, one of the most brutal gangsters in the history of the United States, managed to achieve unprecedented power. Young agent John Connolly, a rising star in the FBI's Boston office, offered Bulger protection in exchange for his cooperation. However, no one protected Boston from Whitey Bulger, a bloody killer who concentrated all the drug traffic in the city in his hands, leaving behind mountains of corpses. The deal between a federal agent and a gangster led to unprecedented corruption in the FBI and the biggest scandal in the history of this department. “Black Mass,” a chronicle of the bloody crimes of the Irish mafia, entered the New York Times and Boston Globe bestseller lists.