Thirty years on, the scars of January 30th, 1972, are still stark on the face of the North. The political and social wounds inflicted on that day, reinfected by the travesty of the Widgery inquiry, and sustained by decades of official denial, still suppurate.
Powerful cinematic screenplay has brought some sense of it to those who are too young to remember the reality. Those who do remember can still recall the disbelief, then the shock and anger at the reports that began to flow from Derry that dark Sunday evening - and the madness that followed.
Bloody Sunday, more than any other single day, shaped the Troubles that have claimed thousands of lives, mutilated whole communities, and spread immeasurable pain and sorrow across these islands.
Other days and nights were marked by ghastly events - Bloody Friday, La Mon, Greysteel, Enniskillen, Omagh, the Dublin and Monaghan bombings - but none had the catalytic effect of the shootings in Derry. If the British government had purposely set out to ignite a 30-year conflagration it could hardly have done better.
For almost three decades, the dead of Derry, their families and community, have been denied truth. The discredited report of Lord Chief Justice Widgery fuelled the sense of injustice and frustration.
It would be impossible to measure the poison which has flowed, not just from the shootings themselves, but from the sustained policy - until recently - of concealment and denial by successive administrations.
Finally, as the Peace Process advances, the layers of concealment are being stripped away.
The proceedings of the Saville inquiry have already shed much light on the events of January 30th, 1972. The active presence of the IRA has been confirmed as has the disparate intentions of other elements.
The core question yet to be answered is why the Parachute Regiment was deployed. Who decided that the Paras - as efficient a killing machine as any to be found - were to be deployed against the marchers, the fringe of stone-throwing hooligans who would accompany them and, perhaps, the odd IRA man with an obsolete rifle, sheltering in the flats? John Hume went to the core of the issue when he asked last week at the Saville tribunal: who gave the political instructions? Answer that and the truth of Bloody Sunday will be known.
There will be those elements who will wish to keep the running sore of Bloody Sunday open for ever. There are others who argue that the focus on one atrocity and not others is selective and an unjustice to other victims and other relatives.
Many dreadful events remain unexpiated and unatoned across the years of the North's Calvary. But if the truth of Bloody Sunday is established and if responsibility is pinpointed, it will be a victory for democratic accountability and for the rule of law. Perhaps, in time, culpability for other dark deeds will be acknowledged and expiated too.
The vast majority of relatives and the ordinary people of Derry - and elsewhere - simply want truth, justice and closure. That they will get these, at least in some measure, from Lord Saville and his colleagues, seems probable.