A British cabinet minister is gunned down by an IRA assassin, leaving an undercover agent to track down the killer before he himself is killed. In the wake of a national outcry, Harry Brown is sent in to find out what he can, with the killer having disappeared in the city of Belfast. For Harry Brown, suspicion is cast upon him from as soon as he arrives in Belfast, during the height of The Troubles, where a single wrong move could result in your immediate danger.