Like a flash of lightning, the leaders' debate on RTE 1 on Tuesday night lit up one of the darkest hours in the recent history of this country. Present in the TV studio were Micheal Martin of Fianna Fail, Mary Lou McDonald of Sinn Fein and Leo Varadkar of Fine Gael.
ary Lou McDonald struggled to explain how she had misunderstood what she had been told by her close colleague, Conor Murphy, Minister for Finance, in relation to the torture and murder of a young Catholic, Paul Quinn (21).
On the face of it, there seemed to be little room for misunderstanding.
As Conor Murphy said at the time: "Paul Quinn was involved in smuggling and criminality and I think everyone accepts that."
Of course, hardly anyone does. The further claim by Sinn Fein that the IRA was not involved has simply served to undermine the credibility of its public representatives.
As it happens, on the evening of the debate, I was just completing another report on the paramilitary 'punishment' system, of which Paul was a victim.
Unusually among the thousands of such incidents down the years, the terrifying last moments of Paul's life are well-known, because family and friends dared to speak out. Most suffer in silence, as is the case of virtually all of the 85 victims from last year.
I will return to Paul and those who poured acid over his memory in a moment, but first to face up to the grim tidings from last year.
The combined total of paramilitary-style shootings and assaults from last year shows a 25% increase on 2018. A surge, in fact.
For some reason, the new IRAs have a preference for shootings. Shooting by appointment, to minimise the risks to the perpetrators, is especially favoured
It is clear that this particular legacy of the Troubles is a recurring nightmare that shows no signs of fading.
It involves loyalists and republicans. Last year, loyalists were responsible for the lion's share of the attacks, some 60%.
However, there is a marked difference between the two in terms of the types of punishments meted out.
Loyalists administering "rough justice", as Gerry Adams once termed punishment attacks, did most of the batterings, a remarkable 49 of the 67 reported assaults.
Like many forms of crime, particularly crime of a sexual nature, these are underestimates and, in all likelihood, gross underestimates.
For some reason, the new IRAs have a preference for shootings. Shooting by appointment, to minimise the risks to the perpetrators, is especially favoured.
Some will have seen the 2017 documentary film A Mother Brings Her Son to be Shot, directed by Sinead O'Shea.
It recounts graphically the terrible dilemma facing a family in a tight, working-class neighbourhood in Derry: turn up at the appointed spot to be shot, or refuse the offer and later face a back-paralysing shot to the spine.
The mother, Majella O'Donnell, duly took her teenage son, Philly, to be shot in both legs.
There is a variation on this kind of dilemma from last year which lies in there somewhere among the official statistics.
It is the case of young man from west Belfast. He was given a similarly grim invitation: present yourself for the appointment, or we will shoot your brother instead. He duly turned up and took the bullet.
There were 18 shootings of mainly young working-class men last year, or one every three weeks. All but two of these were carried out by the new IRAs. The ratio of republican to loyalist shootings was eight to one. It is not clear why this might be so.
It may be that the use of guns, rather than iron bars and cudgels, conveys the impression of a military force in action, to be distinguished from the actions of a mere rabble or some vigilante thugs.
Self-image matters in the paramilitary mindset, as we know from a number of attacks occasioned by perceived slights to a local 'commander'.
Sinn Fein centres were used to collate information on youths and others who came to their notice. Kangaroo courts were sometimes convened but more usually such niceties were dispensed with
The Paul Quinn murder, as well as the broken and mutilated bodies from last year, serve to remind us of the origins of the punishment system and the murky interface between republican militarism and politics.
These intra-community attacks go back to the 1970s. The foremost proponent of 'people's justice' was the IRA and loyalists were rather slower to get in on the act.
The IRA set up 'civil administration' units in the areas it controlled and meted out justice, as it saw it, to anti-social elements in the community.
Sinn Fein centres were used to collate information on youths and others who came to their notice. Kangaroo courts were sometimes convened but more usually such niceties were dispensed with.
Decisions were made on the basis of rumour and allegation and IRA men were despatched to kneecap, or break the limbs of, those being fingered. Should the victim speak out, worse would follow.
The chilling point is that members of Sinn Fein, using Sinn Fein centres, such as Connolly House in west Belfast, were deeply involved in human rights abuses that have no parallels elsewhere in the civilised world.
These abuses continue. In all likelihood, an attack is being hatched by an armchair commander as I write. There is no reason to believe 2020 will be any better than 2019. But the plight of Paul Quinn acts as a rallying-point for the many who oppose mutilation for the cause of Irish unity.
The circumstances, at least for younger Irish people, need to be known more widely.
Paul was lured across the border to a disused cowshed and farmyard. Two of his friends were held down in a neighbouring shed and taunted, "Can you hear your friend squealing for mercy?", as the punishment progressed.
One said later: "They were beating him. You could hear the bars bouncing off him, maybe four or five bars. He was screaming."
This lasted for 25 to 30 minutes and continued for some minutes after the young man temporarily lost consciousness.
The victim's 18-year-old girlfriend, Emma, was summoned on her mobile phone by one of the friends. She found Paul in the byre.
Paul Quinn died on the way to hospital. Every major bone in his body below the neck had been broken. He was just 21 years old. No one was ever convicted for the assault. Sinn Fein continues to deny that the IRA was involved.
Emma emigrated to Australia the following year. It took Conor Murphy 13 years to apologise for his slur on the Quinn family.
Liam Kennedy is Emeritus Professor of History at Queen's University Belfast