The official deadline was 4pm today. But yesterday afternoon, Michelle O'Neill issued a blunt statement (an "enormous bloody spanner" was how one talks delegate described it to me): "Today we have come to the end of the road.
"The talks process has run its course and Sinn Fein will not be nominating for the position of Speaker or for the Executive Office tomorrow."
In ruling out that nomination process, she also ruled out the possibility of the present talks being extended, although Gerry Adams added: "Will we be back, will we get the institutions in place? Yes."
It was a decision that took just about everyone by surprise. While the general view was that a deal wouldn't be done today, there was also a general expectation that the political equivalent of injury/extra time would be added on, leaving the parties to continue negotiating.
But if Sinn Fein isn't planning to talk today, and doesn't want the extra time, then it's up to the Secretary of State to make a decision about what happens next.
The official position is that he has to call another election within a reasonable time frame if a deal isn't done today; but factored into that decision would be his calculation about whether it would be worth encouraging the parties to go on talking if it looked like extra time would produce a deal.
But what happens if Sinn Fein really has opted out of the present process? If it isn't talking, then a deal can't be done.
Would it be willing to start further negotiations after an election? At this point we don't know; and if it doesn't give a commitment to do so, then the Secretary of State may conclude - reasonably, in my opinion - that another election would serve no purpose.
Anyway, I can't imagine he would be willing to facilitate an election simply because Sinn Fein fancied its chances of picking up the 1,200 or so votes that would allow it to eclipse the DUP as the largest party. The next step, therefore, would be a period of suspension - potentially a very long period of direct rule. Yet Sinn Fein has also said that direct rule is unacceptable. So unacceptable, possibly, that it could refuse to agree to a new round of negotiations while it was in place.
Which brings us to what seems to have become its preferred option of British/Irish co-governance.
There has been speculation (I wrote about it here back in January) that Sinn Fein has been thinking beyond an Assembly and calculating that a British/Irish arrangement - something akin to de facto joint sovereignty - would be more useful in terms of advancing its own agenda.
The problem with that calculation is that it would unsettle the DUP. It may not be keen on direct rule (fearful that the Government might push forward on issues like same-sex marriage), but at least it would be Westminster in control.
Also, I'm pretty sure the British and Irish Governments don't actually want responsibility for the political/institutional mess that is Northern Ireland; and certainly don't want it at the same time as Theresa May will be triggering Article 50 and opening up a much wider debate on the British/Irish relationship.
That debate is going to be tricky enough without both Sinn Fein and the DUP bending their ear on all sorts of other internal problems.
In a statement yesterday afternoon, Arlene Foster accused Sinn Fein of behaving as if "they were the only participants whose mandate mattered". She may have a point, because it seems to be the case that Sinn Fein resisted involving the other parties, meaning that no round table talks were possible during this round of discussions.
That said, the SDLP's Colum Eastwood claimed "rigid opposition to compromise on key issues, particularly from the DUP, has made a comprehensive resolution more difficult to reach".
It is, of course, far too early to suggest that a deal cannot be reached, but we are certainly in a very bad position right now. As recently as November 21 - when Foster and McGuinness penned their joint, very upbeat statement about working together - it looked as though the DUP/SF relationship was better than it had ever been.
Today it is worse than it has ever been - which suggests that digging themselves out of that pit may prove extraordinarily difficult. We are now in very dangerous territory. Very polarising territory.
Sinn Fein - Mr Adams in particular - is taking a huge risk at the moment, the sort of risk that could lead to the final collapse of the institutions.
He pulled the plug yesterday afternoon: pulled it on nominations and pulled it on the entire talks process. What he hopes to gain is something that seems to be known only to Sinn Fein's inner circle.
He needs to be careful - overplaying his hand, limiting the DUP's room for manoeuvre, and keeping everyone else in the dark is the stupidest type of negotiation. One thing is for sure, though. The McGuinness era is over - and I'm not convinced that Adams gives a damn about the Assembly.