At the end of Avengers: Endgame, Steve Rogers travels back in time to return each of the Infinity Stones to the exact moment they were taken by the Avengers earlier in the film. Steve does this to prevent multiple alternate realities from existing — ones in which the stones were missing or absent from certain events.
It’s implied that Steve succeeds in doing this, but he never returns through the Avengers’ time travel machine. Instead, Steve returns as an old man and reveals that after he went back in time, he spent the next several decades enjoying his life. What Avengers: Endgame doesn’t explain, though, is whether Steve went back and reunited with Hayley Atwell’s Peggy Carter in the same timeline he’s always existed in, or went and found her in an alternate timeline.
Fortunately, one new fan theory may help clear up some of the confusion over Steve’s unseen time travel journey.
The Theory — A new Reddit post from u/Spomelo argues that Steve may have simply moved between two different timelines at the end of Avengers: Endgame — the one where he created a life for himself with Peggy and the prime reality where he had his meeting with Sam — without affecting his own past.
The Redditor believes that Steve’s time travel journey may have resembled the multiverse adventures that the characters on Agents of S.H.I.E.L.D. embarked on in the final season, which included plenty of timeline hopping. What’s more, the theory posits Steve may have even gotten in touch with some of the S.H.I.E.L.D. characters for help moving between the timelines.
Questions About Time — It seems unlikely, given just how much Marvel Studios seems to be moving on from Agents of S.H.I.E.L.D., that the culmination of Steve Rogers’ storyline in the MCU films might in any way directly reference the characters or events of that ABC series. That doesn’t mean, however, that Marvel won’t use the same timestream logic from Agents of S.H.I.E.L.D. to explain how Steve achieved his hard-fought happy ending.
As of right now, it doesn’t seem like even Marvel has a concrete answer to this mystery either. Back in 2019, the Avengers: Endgame screenwriters said they thought Steve did not live with Peggy in an alternate dimension. However, earlier this year the Russo Brothers said they thought Steve did live with Peggy in a different timeline and simply journeyed back to the prime reality to give Sam the Captain American shield.
In other words, it seems like Marvel fans can pick their own explanations for Steve’s return, at least for the time being.
The Inverse Analysis — Marvel’s Agents of S.H.I.E.L.D. dealt with time and the multiverse enough that it would make sense for Marvel Studios to incorporate some of that show’s time travel mechanics into its films. It doesn’t seem all that likely, based on the strange, uncertain way Agents of S.H.I.E.L.D. currently exists within the MCU canon, but it’s not out of the realm of possibility.
With that said, if fans are ever going to get a straightforward explanation for Steve’s time travel hijinks, there’s a great vehicle for answers coming up soon: Loki. The next Disney+ show promises to deal heavily with alternate realities and time travel, so it wouldn’t be surprising if it somehow addressed or explained the older Steve’s appearance at the end of Avengers: Endgame.
Avengers: Endgame is streaming now on Disney+.