John Connolly and James “Whitey” Bulger grew up together on the streets of South Boston. Decades later, in the late 1970s, they would meet again. By then, Connolly was a major figure in the FBI’s Boston office and Whitey had become godfather of the Irish Mob. What happened between them – a dirty deal to trade secrets and take down Boston’s Italian Mafia in the process – would spiral out of control, leading to murders, drug dealing, racketeering indictments, and, ultimately, to Bulger making the FBI’s Ten Most Wanted List.
20世纪70年代，联邦调查局警探约翰•康纳利（乔尔•埃哲顿 Joel Edgerton 饰）招揽波士顿的爱尔兰裔黑帮头目詹姆斯•巴尔杰（约翰尼•德普 Johnny Depp 饰），为其提供黑帮线报，以联手铲除双方的共同敌人——意大利黑帮。康纳利则对巴尔杰的犯罪勾当睁一眼闭一眼。巴尔杰趁机将他建立的“冬日山岗帮”坐大，从贩卖毒品到倒卖军火无恶不作，成为波士顿史上势力最浩大、最危险的黑帮组织。 影片根据纪实文学《黑弥撒：FBI和爱尔兰黑帮不光彩合作的真实故事》改编。