Unionists can not understand why after swallowing the decommissioning camel, the IRA is refusing to eat the decommissioning flies.
In other words, why it is that the IRA won't say how much of its weaponry has been "put beyond use"?
In the fall out after Tuesday, General John de Chastelain has found himself being cast in the new role as head of an 'International Scapegoats Commission'.
Someone had to be blamed for the way the deal collapsed and it is he who has taken much of the flak.
This troubled peace process has had its share of 'd' words - decommissioning, disbandment, decontamination and demilitarisation - and there have been plenty of 'c' words too - crisis, clarification, clarity and now confidentiality.
It is all right and proper within the rules. Indeed, it is there in black and white in paragraph 26 of the decommissioning scheme.
It reads: "The commission shall ensure that all information received by it in relation to the decommissioning process is kept confidential and that any records maintained by the commission are kept secure. Disclosure of information received by the commission may occur where disclosure is necessary:
to fulfil the commission's duty to report to the two governments."
There is nothing within those rules to say that information should be disclosed to meet the needs of unionists and to help build confidence within that community - confidence that the IRA is really going away.
But unionists clearly wanted something more on Tuesday - something which in their eyes would take decommissioning beyond the "vague process" in which de Chastelain and the IRA do their business.
The senior Ulster Unionist negotiator, Michael McGimpsey, had met the general a week or so before the IRA took him on his latest decommissioning journey.
In that meeting - and in writing afterwards - the arms commission was made aware of the unionist need for greater transparency.
General de Chastelain has taken much of the flak
The inventory they are now demanding is at "the lower end of the scale" in terms of their expectations.
So, on Tuesday, there was an angry unionist reaction when the general disclosed that the IRA had once again insisted on confidentiality.
Within an hour, David Trimble put the deal on hold and held back his contribution to a choreographed sequence of events.
Confidentiality equalled crisis and, live on television, we watched the deal crumble before our eyes.
But can it be salvaged?
On Tuesday, General de Chastelain told us more than we usually hear about the secret process of decommissioning.
For a start, this latest act was "considerably larger" than the previous two.
But it was all delivered in the militaristic speak of "light, medium and heavy ordnance" - a language familiar to the general but not easily understood by others - especially those listening in at Ulster Unionist headquarters.
However, if you read de Chastelain's words across into the IRA's armoury, it is probably safe to assume that he was talking about mortars, rockets, machine guns, rifles and Semtex.
His colleague Andrew Sens attempted to rescue a bad news conference at Hillsborough by saying the latest weapons to be put beyond use "could have caused death or destruction on a huge scale".
Earlier, the IRA said it had planned a further series of meetings with the arms commission.
In all of this, there were the ingredients of a good news story but it was badly told, and as a consequence the deal aimed at restoring power-sharing after November elections in Northern Ireland went on hold.
After the fall out, Sinn Fein and the Ulster Unionists are trying to make things right, but it won't be easy - especially if unionists hold to their demand for "full disclosure" and an inventory of decommissioning so far and the IRA continues to insist on confidentiality.
While some unionists believe they have been conned, there are those on the republican side who sense it is they who have been double crossed.
Where on the peace process map is the middle ground between unionist full disclosure and IRA confidentiality
Not only had the IRA engaged in a third act of decommissioning but, as part of the choreographed arrangements, Gerry Adams had delivered a speech signalling the future peaceful intentions of republicans.
It was not the hoped for declaration from the IRA that the war was over, but unionists, nonetheless, read it as a significant move towards that point.
On the republican side, there are suspicions about unionist demands - and a questioning of their intentions when they seek an inventory on decommissioning.
Is it something that would be written up on the wall at an Ulster Unionist Council meeting as evidence of an IRA surrender?
In a statement on Thursday, the commissioners said that if they were forced to disclose the inventory without the IRA agreeing to it they would judge their positions untenable.
To the outside world this may seem a petty argument over detail, but inside deeply divided Northern Ireland, and inside this place of little trust, this is an argument which won't easily be settled.
Where on the peace process map is the middle ground between unionist full disclosure and IRA confidentiality?