Despite Thor’s beloved Mjolnir getting destroyed in Thor: Ragnarok and him getting an even more powerful weapon — Stormbreaker — during Avengers: Infinity War, Mjolnir could make a convoluted return to the MCU in Avengers 4 and be wielded by none other than Steve Rogers.

Consider everything we’re about to cover as potential Avengers 4 spoilers. You’ve been warned.

On April 30, a redditor going by ilurkthingsreborn posted to the Marvel Studios Spoilers subreddit a lengthy post full of “spoilers” for Avengers 4, claiming to have an inside source. (Supposedly, their previous account ilurkthings was deleted, and with that account, they had accurately predicted a number of plot points in Infinity War via similar leaks.) By Thursday, Huffington Post had codified all of this into the following theory, which includes the bit about Thor’s hammer:

In Avengers 4 the surviving heroes supposedly travel back in time to collect the Infinity Stones for a Stark-built Infinity Gauntlet. Certain set photos have already showing Cap in his Avengers-era costume alongside Ant-Man, meaning that several of them could return to the Battle of New York in some capacity. So this actually makes a lot of sense.

Supposedly, Thor and Cap will fight Thanos directly in 'Avengers 4'.
Supposedly, Thor and Cap will fight Thanos directly in 'Avengers 4'.

The technology allowing them to time-travel will probably relate to the Quantum Realm presented in Ant-Man but also to Tony Stark’s “Binary Augmented Retro Framing.” Both have been a part of speculation so far.

But the really fun part of Avengers 4 happens when — according to the rumors — Steve Rogers has to pick up Mjolnir and use it to fight Thanos one-on-one.

“… at one point bearded Steve and Thor have a fight scene against Thanos where Thor gets blown away and Cap actually ends up weilding Mjolnir because he has finally been found worthy. However I was told that Thanos does end up killing Cap. I’m not sure what plot lines lead to Mjolnir having never broken and it does seem weird that they would introduce stormbreaker in this past movie but this is what I was told.”

Historically, only those deemed “worthy” can wield Mjolnir, so Cap wielding Mjolnir would totally be a huge deal, and it has roots in the comics. His worthiness also was hinted at back in Age of Ultron when everyone took turns trying to pick the hammer up. It wouldn’t budge for anyone until it shifted slightly for Rogers. So does that mean he’s worthy? Or a little bit worthy?

At San Diego Comic-Con 2015 a fan asked Joss Whedon, director of the first Avengers and Age of Ultron, this exact question. Whedon had the best response possible: “Did he fail? Or did he stop?” The idea was left open for future exploration.

Huffington Post’s Bill Bradley picked up on that tantalizing thread in 2016 when talking to Anthony and Joe Russo about Civil War. So is Steve Rogers worthy or not? “I don’t know that might be a …” Anthony Russo said, “that might be a question for future storytellers.” Joe added, “Might be a little too specific for us to answer.” Based on how Bradley describes the encounters, he inferred that there might be more to this tantalizing possibility. So considering we might get some kind of time travel in Avengers 4, it’s entirely possible that we’ll see Mjolnir again long enough for Captain America to use it on Thanos.