Now that fans have been given a tantalizing first glimpse of Avengers: Endgame, questions, theories and opinions are flying across the Internet, thick and fast. As anticipation builds for April 2019, eagle-eyed viewers are pouring over every second of the teaser trailer for clues as to what’s next for Earth’s Greatest Heroes. One theory, however, suggests that it’s not the future that’s important, but the past.

With a snap of his fingers, Thanos wiped out 50% of the population of the universe, including Spider-Man, Scarlet Witch, Black Panther and the Winter Soldier. All of that could be undone by one of Marvel's least respected heroes, however, if this Reddit fan theory is to be believed. When the plot of a movie includes a literal stone that can alter the flow of time itself, it’s a safe bet time travel will be a factor in undoing the previous film's most tragic events.

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Reddit user ak2sup has some interesting ideas regarding the final shot of the teaser trailer specifically, in which Captain America and Black Widow are looking at footage of Scott Lang, who appears to be buzzing in at the gate of the Avengers compound. As Scott talks to the security camera, Cap asks, “Is this an old message?” Natasha doesn’t directly reply, instead saying simply, “It’s the front door.” While at that moment it feels like their reactions are simply due to their disbelief that Ant-Man is still alive (an earlier scene in the trailer lists him as “missing”), further examination of the footage suggests there may be more to it.

First, Scott mentions they met “a few years ago,” referencing the events of Captain America: Civil War. While this would seem to track with the amount of time that’s passed between that movie and Endgame, there’s something more. A close examination of the screen shows the word “archive” in the top corner, suggesting that Cap’s not so out of touch as to suggest that this might be old footage. There’s also the fact that the numbers next to it, though obscured, seem to read "1983." Thus, this theory posits that Ant-Man has somehow traveled back in time, providing a vital key to undoing the damage done by Thanos.

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In the first Ant-Man movie, Scott was shown plans of the Avengers compound and told by Hank Pym it was “one of Howard Stark’s old storage facilities.” When Ant-Man arrived, he was surprised to see that it was, in fact, the newly developed Avengers HQ. The footage in the new trailer shows an old-style gate with a lock and chain rather than the high-tech entrance we would expect, so it’s possible that Scott may have traveled back to when the building belonged to Stark and buzzed the door, not realizing when, exactly, he was.

But how would Ant-Man have been able to travel back in time? The last time we saw him in the post-credits scene of Ant-Man and the Wasp, Scott had just embarked upon a journey into the Quantum Realm when the snap happened, wiping out everyone in the real world that either knew where he was or were able to bring him back (hence why he was listed as missing). Earlier in that scene, Janet Van Dyne tells him, “Don’t get sucked into a time vortex; we won’t be able to save you.” Is this what happened to Scott? Did he get sucked into a time vortex and spit out in 1983?

The van seen behind Scott in the trailer is his ExCon van, a vehicle that just so happens to house a mobile Quantum tunnel device. Reddit user ak2sup's theory suggests that the van's presence is merely trailer trickery, much like when we saw Thor with two eyes in early Infinity War footage so as not to spoil the fact that he lost one in Thor Ragnarok, which hadn’t come out at the time. This aspect of the theory doesn’t seem entirely plausible, as the van may be a crucial aspect of the entire film if we’re to believe that a time-traveling Scott Lang is as important as it appears he is.

Avengers: Endgame logo

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If Ant-Man is able to travel back in time (albeit accidentally) by using the Quantum Realm, then this could be the plan Captain America and Black Widow are talking about earlier in the trailer. It’s no coincidence that the original six Avengers are not only still alive after the snap, but are all seen in this trailer, meaning that a reunion is guaranteed to be in the cards. Avengers: Endgame could see the original Avengers (plus Ant-Man) teaming up one last time, jumping into the Quantum Realm and taking a trip through into the past to defeat Thanos and undo everything he did at the end of Infinity War.

Avengers: Endgame will release on April 26, 2019. Directed by Joe and Anthony Russo, Marvel’s Avengers 4 stars Robert Downey Jr., Josh Brolin, Mark Ruffalo, Tom Hiddleston, Chris Evans, Chris Hemsworth, Jeremy Renner, Chris Pratt, Elizabeth Olsen, Sebastian Stan, Benedict Cumberbatch, Paul Bettany, Samuel L. Jackson, Cobie Smulders, Benedict Wong, Zoe Saldana, Karen Gillan, Vin Diesel, Dave Bautista, Pom Klementieff, Scarlett Johansson, Tom Holland and Anthony Mackie.