On April 15, 2013 Boston, Massachusetts, Police Sgt, Tommy Saunders is pulling security duty on the annual Boston Marathon when the Tsarnaev brothers strike with their homemade bombs in an act of terrorism. In the resulting chaos as the wounded are cared for, Saunders and his comrades join forces with the FBI to get to the bottom of this attack. As the investigation continues, the Tsarnaev brothers realize that the authorities are close to identifying them and attempt to flee the city to continue their fanatical mayhem. To stop them, a police manhunt is performed that would have bloody confrontations and a massive dragnet shutting down the City of Boston to make sure there is no escape from the law.

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.