Avengers: Infinity War ended on a shockingly dark note, but what if the superhero team’s 2012 debut The Avengers was just as dark — we just didn’t know it at the time. That’s what an intriguing new Avengers 4 theory argues, combining some of the most popular theories around (from time travel to Tony Stark making a new Infinity Gauntlet) to cobble together what could potentially be a huge spoiler for the upcoming movie.

In this Avengers 4 theory, Reddit user ch671 asks a simple question with huge ramifications: What if Tony Stark didn’t survive his fall from space at the end of The Avengers?

Remember that scene? Iron Man intercepts a nuclear missile sent to take out the alien invasion (and most of Manhattan) and redirects it up into space where it collides with the alien ship. Then, Tony plummets back down to earth, barely slipping through a shrinking portal in the sky.

Did Iron Man die in 'The Avengers' (2012)?
Did Iron Man die in 'The Avengers' (2012)?

Or so we think.

“Tony Stark actually died when he went through the portal,” ch671 writes, “and the future Tony Stark replaced him and made it back through time at that exact moment!”

If you look closely, we never actually see Iron Man go through the portal. He’s falling through space, and then, all of a sudden, he’s back on Earth. So what if he never made it into the portal at all? Or what if he got trapped in some sort of in-between zone?

“Could those two seconds of yellow lightning have anything to do with the quantum realm/time travel,” ch671 writes. “We know from Ant-Man and the Wasp that Quantum Realm is yellowish in color, exactly like those two seconds.”

The Quantum Realm in 'Ant-Man and the Wasp'.
The Quantum Realm holds more mysteries than most realize in the MCU.

Now that we’ve mentioned the Quantum Realm it’s time to bring up time travel. It’s been all but confirmed that Avengers 4 will feature time travel as a key plot device, allowing the remaining Avengers to revisit moments from previous movies as part of their plan to undo Thanos’s Snap. Presumably, this has something to do with collecting the Infinity Stones, which ties into another popular theory that Tony Stark will make his own Infinity Gauntlet to balance out the original.

In that case, The Battle of New York from The Avengers is an obvious place to start, since, as ch671 notes, two of the Infinity Stones were present at that time: “The Space Stone (Tesseract) and Mind Stone (Loki’s scepter).”

The Avengers would need to get their hands on those Stones without throwing off the entire timeline, and Tony Stark’s unseen death provides the perfect cover. If future Iron Man can slip in at just the right time he’d create a grim (but clean) time loop without anyone else even noticing. This also offers Marvel a clever way to write Robert Downey Jr. out of future movies once his contract expires next year, while giving The Avengers a surprisingly dark ending six years after its release.

Of course, there are plenty of flaws in this theory, the primary one being how Avengers 4 Iron Man can exist in the first place if he died in the 2012 movie. But this is a superhero movie, I’m sure they can figure out some clever way to explain it.

Avengers 4 hits theaters on May 3, 2019.