A British Cabinet Minister is gunned down outside his home in London by a member of the Provisional IRA. Security protocols are activated, but the assassin evades them and successfully escapes to Belfast. In the aftermath of the incident, rash decisions are made by politicians seeking revenge, and the Ministry of Defence responds by sending Captain Harry Brown (Ray Lonnen) - a special forces soldier who has done deep cover work in hostile territory - into the Falls Road area of Belfast, notorious for civil unrest and Republican activity. Harry's mission is to infiltrate the local nationalist population, uncover the identity of the assassin, and kill him in his own neighborhood - proving to the IRA that they are not safe, even in their "own back yard".
When a Cabinet Minister is shot outside his home by a member of the Provisional IRA, the military send Captain Harry Brown to Belfast to infiltrate the local population where the assassin has fled and kill him on his own ground.
Having been accepted in Belfast, Harry plays a game of cat and mouse with the locals while the British government continue their own investigation into the assassination.
The net starts to close in on both Harry and Billy Downes in this final episode. As the fight for survival reaches its climax, innocent people are caught up in the game of cat and mouse.