WARNING: MAJOR SPOILERS FOR AVENGERS: ENDGAME
Across three hours of action and emotional pay-offs, Avengers: Endgame will probably leave you with more than a few questions.
When there's time travel involved, everything gets muddled and those tricky time paradoxes have a way of sneaking up on you and breaking your brain — I'd be lying if I said I totally get how Inception works.
The Marvel folks even poked fun at the concept by referencing a tonne of time travel movies and emphasising that the gang will have to strictly follow the rules of time travel, that is until Scott Lang realises, to his horror, that "Back to the Future is bullsh*t?!".
Now, this explainer of the time travel in Endgame is only the sense I've managed to eke, and it's certainly not gospel. Surely the folks at Marvel, or the Russo brothers will start breaking it down soon — we hope.
And I should say I went over it with increasing frustration for 36 hours, talking it out with everyone I know who had seen it, convinced it doesn't make sense, that there was a plot hole or a paradox, until my colleague Sam van Grinsven came up with the only theory that we thought would explain it, based on what's been revealed so far.
So here goes.
First some timeline establishing: Endgame opens in 2018, 22 days after Thanos' "snapture" in Infinity War. When Thor decapitates Thanos and discovers the Infinity stones have been destroyed, it's still 2018. Then Endgame time jumps five years to 2023.
At this point, Scott Lang/Ant-Man is released from the quantum realm, where he was trapped the whole time. But because time moves differently in the quantum realm, he had only been trapped, from his perspective, for five hours.
(By the same logic, Janet van Dyne, who had been trapped in the quantum realm for 30 years, should only have aged 30 hours, though she appears to have aged 30 years — however, Marvel boss Kevin Feige has hinted there are levels within the quantum realm, and for narrative purposes, it made sense to have Janet come out as someone closer to Michael Douglas' age than Evangeline Lilly's age.)
In 2023, after figuring out how to "control the chaos", the remaining Avengers decide to go back in time to steal the Infinity stones from various points in time, specifically:
— Captain America, Iron Man, Hulk and Ant-Man to New York (space stone/tesseract, mind stone/Loki's sceptre and time stone/Eye of Agamotto) in 2012 during the events of The Avengers
— Thor and Rocket to Asgard (reality stone/Aether) in 2013 during the events of Thor: The Dark World
— Rhodey and Nebula to Morag (power stone/orb) and Black Widow and Hawkeye to Vormir (soul stone) in 2014 during the events of Guardians of the Galaxy Vol. 1.
After fumbling the tesseract retrieval in New York, Captain America and Iron Man go from 2012 to 1970 from which they steal the tesseract (at that time in the possession of SHIELD) and Pym particles (we see Cap take four vials when they only need two for the return trip to 2023).
When Hulk tries to convince The Ancient One to give him the time stone, she refuses, explaining that if she lets him take it, it would split the timeline in two — the original timeline would become one in which the time stone doesn't exist from 2012 onwards, heralding disaster with the Sanctums unable to protect Earth.
Hulk promises that once the Avengers had all six Infinity stones and unsnapped Thanos' genocide, the stones would be returned to the point from which they were taken, reforming the split timelines as if the stones had never been removed.
It would've all worked, except in 2014, 2014-Thanos discovered the plan and replaced 2023-Nebula with 2014-Nebula on the return journey back to 2023.
In 2023, 2014-Nebula opened the time portal and allowed 2014-Thanos and his army (not sure how that works when they don't have any Pym particles) to invade 2023, just as Hulk successfully snaps back into existence all the creatures who had been erased by Thanos in 2018.
Hulk specifically says he tried but he couldn't bring Black Widow back from the dead. That would also be true for 2018-Gamora who died the same way on Vormir.
When 2014-Thanos and his army are erased by Iron Man in 2023, it's assumed that they've been snapped out of existence like 2018-Thanos did half the universe.
But what if that's not what Iron Man did?
This is where I was really confused for a while. Because if Captain America went back and returned all the Infinity stones, and Thor's hammer, to the moments from which they were borrowed (in 2012, 2013 and 2014), then the two split timelines would remerge as one (as The Ancient One's little demo so insistently told us) and time would continue from those moments as if nothing had changed back then.
Hydra would still steal the sceptre and create Scarlet Witch, Hela would still destroy Thor's hammer and so on, until all the Infinity stones would once again be collected by Thanos who would snap half the universe away, and the Avengers would go on the time travel mission to reverse it.
As Thanos said at the beginning of Endgame, "I am inevitable".
Except that 2014-Thanos has been snapped out in 2023, taking him out of the timeline, which in theory would change what happens from 2014 onwards. If 2014-Thanos doesn't go on to amass all the Infinity stones, then he wouldn't be on the Asgardian refugee ship to kill Heimdall and Loki, or sacrifice Gamora on Vormir.
In which case, the events of Infinity War wouldn't happen and those guys and Black Widow and Iron Man would still be alive, and old-man Captain America wouldn't find Sam and Bucky by that lake.
Uh oh. Paradox. Or worse, plot hole.
But there is a way in which it could be explained. A way for 2023 to remain the same (with Iron Man etc still dead) after the timelines were remerged when Cap returned the Infinity stones is if Iron Man didn't snap 2014-Thanos and his army out of existence.
What if Iron Man merely snapped all those 2014 characters, including the ones killed in the 2023 battle including 2014-Nebula, back to their place in 2014, effectively resetting them on their original paths?
A path in which 2014-Thanos never finds out about the 2023-Avengers' adventures in 2014.
There's nothing in the mythology of the MCU that says the Infinity Gauntlet can only snap things out of existence completely — it does have a time stone so maybe it can also reset time to what it should be in 2014.
It makes sense that Iron Man would see this as the only course of action because taking 2014-Thanos out of the post-2014 timeline completely would likely mean that his daughter with Pepper, Morgan Stark, may never have been born.
And he said very clearly near the start of Endgame he would, referencing Morgan, "keep what I found, have to, at all costs".
The cost was his life (and that of Gamora's, Black Widow's, Loki's and Heimdall's) for Morgan's.
Of course, that's all speculation. The Russos, Feige or Marvel could come out and say there are now multiple timelines or parallel universes or something completely different.
The Russos have said we shouldn't assume that just because the MCU has so far worked in a linear fashion that it will in the future.
For one thing, with all the vanished now returned, they've aged only moments when those who remained have aged five years. That's got to be reconciled in-universe, at least emotionally.
Presumably, some of those questions will be answered in Spider-Man: Far From Home in a couple of months. Feige came out last week to confirm Far From Home is now the official end of MCU's phase three and not Endgame as previously reported.
And there are those confirmed movie and TV projects involving characters who remain dead — Black Widow, Vision and Loki. We assume they're going to be prequels, but, hey, this is a superhero universe with time travelling and magic, anything could happen.
Avengers: Endgame is in cinemas now.
The Hollywood star is 70 but has no plans to retire from acting.