It's January 30, 1972 and civil rights leader Ivan Cooper (JAMES NESBITT) is trying to organize and then lead a peaceful march and protest in Derry concerning Britain's internment without trial policy that's been in place for a year. A Protestant Member of Parliament, Ivan wants things to run smoothly and thus asks the I.R.A. to stay away. He also tells the town's young men, such as Gerry Donaghy (DECLAN DUDDY) who has a Protestant girlfriend, not to cause any trouble.
The British forces, however, are preparing for the illegal march and have decided to use it as an opportunity to arrest various residents they deem to be troublemakers. Accordingly, Major General Robert Ford (TIM PIGOTT-SMITH) has arrived to make sure that the operation, run locally by Brigadier Patrick MacLellan (NICHOLAS FARRELL), is a success.
The plan is for various armed members of the first Battalion of the Parachute Regiment to ambush those on their wanted list during the parade, and as the events draws closer, they prepare for their mission. Meanwhile, local police officer Chief Supt. Lagan (GERARD McSORLEY) tries to persuade MacLellan to call off the operation, knowing it will lead to unrest and potential violence.
As Ivan and others, including Kevin McCorry (ALLAN GILDEA), Eamonn McCann (GERARD CROSSAN) and Bernadette Devlin (MARY MOULDS), lead the march through the town, a splinter group of the parade breaks off and confronts those manning a British blockade. As words and objects fly, and as the British Paras prepare for their assault, Ivan tries to maintain the peace and avoid the inevitable bloodshed that's to follow.