While "Avengers 4" is closely intertwined to "Avengers: Infinity War," Marvel is keeping the details on the yet-to-be-titled fourth installment close to its proverbial chest. However, a new fan theory outlines just how things may play out and it may have something to do with time travel.

As with any superhero films, the Avengers will most likely win the war against Thanos (Josh Brolin), but Reddit user onex7805 thinks there is really no way to defeat him, not at least in the traditional sense. So instead of fighting him continuously, the Avengers will have to go back in time in order to prevent the Mad Titan from obtaining all Infinity Stones.

As the Redditor points out, there have been reports that "Avengers 4" will feature flashbacks to the 1940s, during Steve Rogers' tenure as a World War II soldier, and to the first "Avengers" movie that brought the superheroes together. It has been strongly hinted as well that the fourth installment will soft reboot the Marvel Cinematic Universe (MCU). This is supported by Marvel President Kevin Feige's statements that "There will be two distinct periods. Everything before Avengers 4 and everything after," and that the "Infinity War" sequel will serve as a conclusion to the current MCU.

The theory posits Iron Man (Robert Downey Jr.) and the team will use the Time Gem, which is capable of reversing time, to change history. As planned, it will stop certain things from happening. However, messing with the timeline will also rewrite several of the Avengers' past, stopping their transformations as superheroes, or erasing them from history altogether.

This should retire Marvel's veteran characters like Captain America (Chris Evans), Iron Man, Black Widow (Scarlett Johansson), and more without killing them. It will also soft reboot the MCU in the process like how "Days of Future Past" rebooted the "X-Men" timeline. In the end, none of the original members die, but none of them exist either. Only newbies like Ant-Man (Paul Rudd), Doctor Strange (Benedict Cumberbatch), Captain Marvel (Brie Larson), Black Panther (Chadwick Boseman), and the Guardians of the Galaxy will remain instead.

It is an interesting theory, but as some commenters point out, resolving the conflict by a simple time travel would put the 22-movie climactic buildup to waste. While some characters like Quicksilver (Aaron-Taylor Johnson) died in the line of duty, the MCU has also never had a major death so far.

It is difficult to imagine the MCU without the likes of Cap or Tony Stark. Fans have grown so attached to them, and even the actors themselves think it will be hard to say good-bye to their characters on screen. However, in order to expand and bring the franchise to new heights, tough changes should be made. Fans will have to wait and see.

"Avengers: Infinity War" releases in U.S. theaters on May 4, 2018, to be followed by "Avengers 4" on May 3, 2019.