There is no coming back for the Prime Minister's Brexit deal from the scale of a defeat by 432 to 202, the worst defeat by a government for more than a century.
In all normal circumstances a Prime Minister would resign when suffering such a humiliation on their central policy - and a policy Theresa May herself said today would "set the future of this country for generation".
But these are neither normal times Theresa May is not a normal Prime Minister.
It is highly unlikely that May's Tory and DUP critics will vote with Corbyn to eject her and the Government.
So after that vote, if she survives, she will endeavour to explore what kind of Brexit, if any, would command support from the Commons, via meetings she will hold with her DUP partners and "senior parliamentarians from across the house".
If those meetings "yield ideas that are genuinely negotiable" - in the words of a Downing Street official - Theresa May will then explore with EU negotiators and leaders whether they would agree to a revised Brexit (which would, as a minimum, have to include a time-limited backstop - and probably much more).
My EU sources say talks cannot possibly start until May has some confidence about what would achieve a majority in the Commons.
So we are, as the PM warned we could be a few days ago, in uncharted territory.
And given the uncertainties and the scale of negotiating and legislative challenges ahead, it is now almost inconceivable the UK will be leaving the EU on 29 March - and the question is whether the delay to Brexit would be temporary or permanent.