U.S. Marine Corps Force Recon sniper, Gunnery Sergeant Bob Lee Swagger, is on a mission in Eritrea with his spotter and friend Donnie Fenn. They help an allied convoy evade the enemy, but Fenn is subsequently killed in the firefight against the enemy militia forces. Three years later, Swagger, now a disillusioned civilian, is living in self-imposed exile at a secluded log cabin. At the office of a unnamed private military company in Langley, Virginia, retired US Army colonel Isaac Johnson and his employees review Swagger's combat operation report and DD Form 214. Johnson visits Swagger and requests his expertise to prevent a pending assassination of the U.S. president. Johnson gives him a list of possible assassination sites, and Swagger concludes that Independence Hall in Philadelphia is most likely. As Swagger is working with Johnson's men to find the assassin, the Ethiopian archbishop is killed instead while standing next to the president. Swagger is betrayed when he himself is shot by a corrupt Philadelphia police officer, though he manages to escape. The conspirators frame Swagger as the assassin, and a manhunt ensues. Swagger subdues an inexperienced Federal Bureau of Investigation agent, Nick Memphis, and steals his car and his service pistol crashing it into the Delaware River. He then clings to the side of a boat to evade pursuing policemen.