Prime Minister Boris Johnson faces a cross-party alliance to defeat his plans to leave the EU, deal or no-deal, at the end of October.
We are living in extraordinary times, so how are events likely to pan out?
- Can MPs put in laws to stop a no-deal Brexit?
MPs from both sides of the house will on Tuesday try to take control of the Commons.
If they're successful, Wednesday's order of business will be taken over to guarantee a time to debate a new law to block a no-deal Brexit.
Under rules known as SO24 - which stands for Standing Order Number 24 - lawmakers can ask Commons Speaker John Bercow to hold an emergency debate.
- But time is ticking, isn't it about to run out?
Time is certainly not a commodity no-deal opposing MPs have aplenty.
The urgency is even greater by the virtue of the PM's decision to suspend Parliament shortly after MPs return from their summer recession .
New laws need to be debated and signed off by both MPs and the Lords - a process that usually takes weeks but could be hurried through in three days.
Although it's not scheduled to sit on Friday, MPs could have an emergency session - it comes amid speculation the Lords could sit over the weekend to get new laws passed.
September 9 is the earliest day Parliament could be suspended, leaving MPs locked out of making new laws until October 14.
- What exactly will MPs be voting on?
The legislation put forward by a cross-party group, led by the Labour MP and Brexit Select Committee chairman Hilary Benn and Tory former Foreign Office minister Alistair Burt would require a delay to Brexit unless there was a deal or Parliament explicitly backed leaving the EU without one by October 19.
The snappily-titled European Union (Withdrawal) (No. 6) Bill 2019 also has the support of Tory former Cabinet minsters Philip Hammond and David Gauke, a sign of how the rebel ranks have been bolstered following the change in prime minister.
Under the terms of the Bill, the Government must ask the European Union for a delay to Brexit until January 31, 2020 if no agreement has been reached and MPs have not agreed to a no-deal exit.
If the European Council proposes an extension to a different date then the Prime Minister must accept that extension within two days, unless the House of Commons rejects it.
- What are they key dates for the diary?
It's expected to be a busy week in the House of Commons and Lords.
As MPs are attempting to rally support for their sides of the Brexit argument, here are the main dates.
- What has the Prime Minister said?
After an emergency Cabinet meeting, the Prime Minister used a statement in Downing Street to urge MPs not to back a "pointless" delay.
Such a move would "cut the legs out" from under the UK’s negotiating position with the EU.
It has been made clear to Tory MPs that they will lose the whip if they back the plan and, in a dramatic raising of the stakes, allies of Mr Johnson said he would seek a snap general election if Tuesday’s measure is passed.
- Will there be an election?
A senior Government source said Mr Johnson could go to the country on October 14 – unusually for Westminster elections, that is a Monday rather than a Thursday – if he is defeated on Tuesday.
For voters to head to the polls would require the support of two-thirds of MPs under the provisions of the Fixed-term Parliaments Act, but some are reportedly suspicious the PM would seek to alter the election date to delay it until after Brexit.
Meanwhile Opposition leader Jeremy Corbyn said a vote of no confidence is "very much there on the table" as he pledged to "do everything we can to stop" no-deal.
If the vote won the support of a majority of MPs, there would be 14 days for another government to be formed, otherwise Parliament would be dissolved and a general election triggered.
- Are there other ways the PM’s plans could be thwarted?
The PM faces threats from many angles, with legal challenges coming in courts across the UK.
A cross-party group of MPs and peers who want to block Parliament’s suspension will have the full hearing of their application in Edinburgh on Tuesday.
On Thursday, the High Court will consider a judicial review request from Gina Miller, the businesswoman who successfully challenged the Government over the triggering of the Article 50 process to start the Brexit countdown.
She, too, wants to challenge Mr Johnson’s suspension of Parliament.
And in Belfast, a judicial review against the Government by a campaigner arguing that no-deal could jeopardise the Northern Ireland peace process is scheduled for September 16.