CIA agent and former U.S. Marine war veteran, James Silva, leads a Special Activities Division team code-named Overwatch to raid a Russian Federal Security Service safe house in the United States. Under the remote supervision of James Bishop and his team, the mission is to locate and destroy shipments of caesium before the highly radioactive substance can be weaponized. In the ensuing firefight, most of the Russians and Overwatch operative Greg Vickers are killed, but critical intelligence on the caesium is destroyed. Silva executes the last survivor, a teenager who warns him that he is making a mistake.