Gary Hook, a new recruit to the British Army, is sent to Belfast in 1971 in the early years of the Troubles. Under the leadership of the inexperienced Second Lieutenant Armitage, his platoon is deployed to a volatile area where Irish Catholics, Irish Republicanism , Ulster Protestants, and Ulster loyalism live side by side. The unit provides support for the Royal Ulster Constabulary as it inspects homes for firearms, shocking Hook with their rough treatment of women and children. A crowd gathers to protest and provoke the British troops who, though heavily armed, can only respond by trying to hold the crowd back.