The findings of the investigation into the 1972 Claudy bombings - in which nine people were killed - are likely to be highly critical of both the Catholic Church and the police.
The report by Northern Ireland's Police Ombudsman is expected to confirm that the authorities at the time were aware of the suspected involvement of a priest in the atrocity widely linked to the IRA, but failed to arrest him.
Instead, it is claimed that a secret deal was done to move Father James Chesney across the border into County Donegal.
He died in 1980, without having been questioned about his alleged role, much to the anguish of people like Merle Eakin, whose eight-year-old daughter Kathryn died in one of the three blasts.
Kathryn was enjoying her summer holidays, and was earning pocket money by cleaning the windows of her parents' shop when a car-bomb exploded on the road beside her.
Whoever left it there would have seen her, but decided not to give the little girl with the sponge and bucket any warning. A short time later, Kathryn died on the street.
In an interview on the 20th anniversary of Kathryn's death, her mother spoke of her innermost thoughts and deepest pains about losing her daughter.
"Every time I go to a wedding, I think it could have been hers," she said.
She didn't mention how she felt at Christmas, at birthdays and other anniversaries. She didn't need to.
Like so many families who lost a loved one in the Troubles, every day since has been a battle.
More than 3,600 people were killed over 30 years. The Claudy report, just like the recent report into Bloody Sunday, will shine a very bright light on families who feel a sense of loss, compounded by a feeling of injustice.
For the past 38 years, rumours of Father Chesney's involvement in the Claudy bombings have been swirling through the Londonderry village.
If the ombudsman's report substantiates those rumours, there will be questions for the Catholic Church to answer.
There will also be questions for the police and politicians, though most of those involved - including the then Northern Ireland Secretary Willie Whitelaw - have either retired or died.
Unionist politicians are also expected to challenge Sinn Fein's Martin McGuinness to say what he knows about Father Chesney.
Mr McGuinness is currently Northern Ireland's Deputy First Minister, but back in 1972 he was the second in command of the IRA in Derry. Did he know Father Chesney?
In a statement in 2002, he insisted he had never met him. But that is unlikely to stop unionists like the DUP's Gregory Campbell continuing to ask the question.
Arguably, the most difficult question of all, though, is for Prime Minister David Cameron. What is exactly is the new coalition government going to do about the unresolved controversies, and hundreds of unsolved murders in Northern Ireland?
We know what he is not going to do.
On the day the £200m Bloody Sunday report was published in June, Mr Cameron told the Commons: "Let me reassure the House that there will be no more open-ended and costly inquiries into the past."
A South African-style truth and reconciliation process has also been ruled out.
The police have an historical inquiries team investigating unsolved killings, but it is limited in what it can achieve.
At a time when government money is in short supply, it is perhaps the wrong moment to be starting a debate about what more can be done to examine Northern Ireland's troubled past.
However, the Claudy report may make such a debate unavoidable. In addition to Kathryn Eakin, the eight other victims ranged in age from 15 to 65 and came from both the Catholic and Protestant communities.
The findings of the ombudsman's investigation are likely to make uncomfortable reading for the government, the police and the Catholic Church.
However, nothing will compare to the pain felt by the families of the victims of the bombs.