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.