(CNN) -- After three and a half years of torturous negotiations and political machinations, this was meant to be it.
Boris Johnson planned to put his new Brexit deal to a vote in Parliament, on a historic, emergency session that promised to finally bring clarity to the process.
But in the world of Brexit, nothing can be taken for granted. And sure enough, what was billed as Brexit's "Super Saturday" turned into yet another bout of can-kicking equivocation.
So what exactly happened -- and where do we go from here?
What just happened?
The government's intention was to hold a straightforward vote on Johnson's deal, signed in Brussels on Thursday.
But its plans were scuppered when lawmakers passed an amendment crafted by former Conservative government minister Oliver Letwin, who has worked to prevent the UK from crashing out of the EU without a deal.
The amendment said Parliament would "withhold support" from Johnson's Brexit plan until after the other bits of legislation required to implement it are passed.
Had Johnson won a vote on his plan on Saturday, he would have avoided the need to send a letter to the EU requesting an extension to the Brexit process until January 31. That letter is required by the "Benn Act," a piece of legislation designed to avoid a no-deal departure on October 31.The law required it to be sent by 11 p.m. London time in the event that Parliament failed to approve a Brexit deal.
But Letwin and his allies were concerned that, if the deal was approved and the provisions of the Benn Act fell away, a chaotic departure could still happen by accident on October 31 if, by then, lawmakers had failed to pass the complex set of legislation that's required to enact the Brexit deal.
Downing Street is was livid at the vote. The failure to pass his deal on Saturday means the Benn Act kicked in, requiring that extension to be requested.
Johnson had staked his political reputation on delivering Brexit by October 31, and now that's in the balance.
So did Boris Johnson ask the EU for a delay?
Immediately after the vote, the Prime Minister seemed to imply that he would not. "I will not negotiate a delay with the EU, and neither does the law compel me to do so," he said. "Further delay will be bad for this country."
But the law is clear: The government was required send that letter. There is no ambiguity -- the Benn Act even sets out the wording.
In a bad-tempered briefing with journalists after the vote, the Prime Minister's official spokesman refused repeatedly to say whether Johnson would send the letter, or whether someone else in the government would send the letter, or whether the the government would flout the law and not send the letter at all. "Governments comply with the law," was all the spokesman would say.
Boris Johnson later told EU Council President Donald Tusk by phone that he would indeed send the letter, an EU official told CNN. Tusk would then begin consultations with EU leaders on next steps, a process that could take a few days, the official said. "Waiting for the letter," Tusk wrote on Twitter.
What happens next in Parliament?
In the turmoil after the vote, the leader of the House of Commons, Jacob Rees-Mogg, indicated that the government would bring forward another vote on the deal on Monday.
"In the light of today's decision I should like to inform the house that Monday's business will now be a debate on the motion relation to Section 13 -1B of the European Union Withdrawal Act 2018 and I shall make a further business statement on Monday," he said.
Rees-Mogg was referring to a section of the Withdrawal Act that provides for a vote in the House of Commons on the result of a negotiated agreement with the European Union -- a so-called "meaningful vote." Theresa May had three of those, and lost all of them.
Ordinarily, the same provision can't be voted on twice in the same parliamentary session. That convention scuppered May's plans to hold a fourth vote on her withdrawal deal. The Speaker, John Bercow said he would rule on the matter on Monday.
Is it more or less likely that Johnson will get his Brexit deal passed?
The result of the Letwin amendment is that Johnson was robbed of a straight up-or-down vote on his Brexit deal. Had the Prime Minister been able to get the deal through the House of Commons, against all the odds, it would have been a moment of particularly sweet victory.
Downing Street aides are furious, since they believed that they had enough votes in the bag, even without the 10 MPs of the Democratic Unionist Party, whom Johnson abandoned when they refused to sign up to his deal earlier this week.
All eyes turn to Monday's vote, when the government will hope that it can demonstrate parliamentary backing for Johnson's bill. But the fact is, to get Brexit done by October 31, as the Prime Minister has repeatedly promised, he must now get all the stages of the Withdrawal Agreement Bill through the House of Commons, the House of Lords and get it in front the Queen for Royal Assent. Only then will the provisions of the Benn Act fall away.
Since he threw out 21 members of his own party for voting in favour of the Benn Act, Johnson has a majority in Parliament of mninus 40. And the Democratic Unionist Party, which nominally props up his minority. government, is furious at being ditched.
As Johnson's predecessor Theresa May found out to her cost, getting controversial legislation through the House of Commons when you don't have a majority is notoriously difficult.