Jim Terrier (Sean Penn) is a former special forces soldier who, in his 50s, has become a black-op mercenary. He is part of a team deployed in the Democratic Republic of Congo in 2006, under the cover of providing security to local projects. He falls in love with Annie, a fellow expat working as a doctor in a local hospital. During this period, even though civil war has wracked the country, large multinational mining companies continue to profit from the country’s mining industry. After the Minister of Mining announces his plans to declare contracts with the mining companies unjust and renegotiate the terms, the mining companies hire Jim’s team to assassinate the Minister, to ensure their access to the rich mineral resources. Jim delivers the fatal shot from a sniper rifle and flees from Africa, leaving Annie behind. After that, Jim retires from his mercenary career.
Eight years later he returns to DRC as a charity worker to build wells. One day he is brutally assaulted by a local hit squad, but he manages to kill them all. While searching the attackers’ bodies, he finds signs that the attack was not random and that he was the target. Scared and suspicious, he flees to London to meet an ex-mercenary colleague, who reveals that Cox, their ex-boss in the Congo assassination, has formed a large international security firm offering its services to major clients, such as the Pentagon. The firm’s head wants to eliminate all of the former members of the assassination squad, as revelations of their former activities could hinder the development of the new firm, so the firm’s hit teams chase Jim around the clock, meanwhile killing his friends and kidnapping Annie.
However, Jim still keeps highly compromising materials that can reveal Cox’s role in the Congo assassination and uses it to lure Cox and his team to a bullfight in Spain, threatening to expose their complicity unless they trade Annie for the evidence. Unknown to them, Jim makes a deal with Interpol to deliver them and provide evidence to aid their ongoing investigation. Despite battling severe head trauma suffered from his violent past, Jim defeats the mercenaries sent to kill him. As he struggles to help Annie escape to safety, Cox discovers them. Jim is wounded but manages to shoot Cox, who is then gored by a loose bull. Interpol arrive and take Jim into custody, though Agent Barnes promises to do what he can to help Jim avoid doing more jail time than necessary.