It's on a different scale from the grief of Omagh, but today will place a heavy burden on the Police Ombudsman, Ms Nuala O'Loan, and on the Chief Constable of the Police Service of Northern Ireland, Sir Ronnie Flanagan.
This morning Ms O'Loan will present to relatives of the victims a summary of her investigation into the police handling of the "Real IRA" bombing of August 1998, which claimed 29 lives, including that of a woman heavily pregnant with twins. Later this afternoon Ms O'Loan will publish the summary at a press conference in Belfast. It is expected to be highly critical of Sir Ronnie and the Special Branch.
There's a sense of a power struggle being enacted here between two strong personalities - that of Ms O'Loan and Sir Ronnie - who both cherish and know the value of their independence and won't easily concede any ground on that closely guarded autonomy.
At the time of writing, it appears there must be a winner and loser in this battle. And that could have very serious and damaging consequences for the new police service as it tries to find its feet.
And with unionists and nationalists lining up along traditional polarised lines to respectively support Sir Ronnie and Ms O'Loan, the fallout from this dispute could also adversely affect the political process. There is a lot at stake here.
But the fact that it is a summary and not the full report itself that is being presented today may be of some significance.
Sir Ronnie, it is understood, perceives the style and wording of the draft report as being unfairly loaded against himself, some of his senior officers and the Special Branch. The language used to make that point from his office was very strong. A PSNI spokesman said the draft report contained "significant factual inaccuracies, unwarranted assumptions, misunderstandings and material omissions".
However, should the presentation of the summary be softer in tone than the draft report then there could be some easing of the tensions between the PSNI and the Police Ombudsman. But at the time of writing, that appeared unlikely. Irrespective of the tone, Sir Ronnie is expected to face complaints from Ms O'Loan of serious deficiencies in the RUC handling of the Omagh investigation.
These will focus first on reported warnings issued to the RUC that on August 4th, 1998 - 11 days before the bombing - police were told of weapons being smuggled over the border and into Omagh for an attack on police on August 15th, the day of the explosion.
Ms O'Loan is also expected to make reference to an informant codenamed Kevin Fulton, who reportedly told a police handler two days before the explosion that an imminent attack at an unspecified location was expected from the "Real IRA". However, she may judge that this information was not sufficiently detailed to allow police act upon it.
However the main concentration in her findings is expected to be on the RUC investigation after the bombing. The findings are likely to point to serious faults and flaws in how senior RUC personnel, up to and including Sir Ronnie Flanagan and the Special Branch, handled the investigation.
And to bolster her argument she is likely to cite an internal RUC review of the investigation, which itself was critical of the police inquiries.
Sir Ronnie has not yet answered criticisms in the draft report, stating that he still needs more time to complete his response. So, in a sense, what we will have today is the case for the prosecution from Ms O'Loan with the defence case from Sir Ronnie to come later.
Sir Ronnie and Ms O'Loan, representatives of the operational and accountability sides of policing, will act utterly professionally of course as this drama unfolds. But one can't avoid detecting a degree of mutual personal animus between them. Sources say that while their dealings have always followed proper protocols, Sir Ronnie and Ms O'Loan are not in any way shy in fighting their particular corners. Both are very single-minded. But if there is no steadying hand here, this could have damaging ramfications both for the police and for the political process.
The whole emphasis in recent months has been in establishing, for the first time, a police service that has the loyalty and allegiance of both nationalists and unionists.
However, this particular struggle is now being depicted as a confrontation between unionism and nationalism, as in Sir Ronnie defending and Mrs O'Loan attacking the old RUC and the Special Branch.
Both would deny this interpretation. But with, for instance, Mr Sammy Wilson of the DUP, who is on the Policing Board, complaining of the "Ombudsman's Gestapo" and Sinn FΘin saying this is just further evidence of Special Branch waywardness, there is obvious potential for further divisions over politics and policing.
This will also be an important test of the Policing Board, composed as it is of unionist and nationalist politicians, and independents, some of whom are perceived as nationalists and some as unionists.
The challenge will be for its members to present a united front as Ms O'Loan and Sir Ronnie continue their tussle, and to prove that the board can be above this dispute.
But primarily, today is going to be particularly distressing for the bereaved victims of the Omagh bombing and those who carry the physical wounds and mental scars of that dreadful day in August 1998.
This morning the terrible memories will be further exacerbated as Ms O'Loan meets the families in Omagh to brief them on the findings and recommendations of her investigation.
It won't be easy but it is necessary, the families say. Generally they favour any action that will bring them closer to the truth about Omagh.
Gerry Moriarty is Northern Editor of The Irish Times