Although Back to the Future’s ending was always oddly dark, the story only gets creepier the more I think about its ending. Back to the Future’s ending is undeniably clever in terms of how the sci-fi comedy sidesteps the complications of time travel by jumping straight into the next big twist. Doc Brown arriving from the future and telling Marty that “Something’s gotta be done about your kids!” leaves viewers with no time to really think about how Back to the Future’s timelines add up.

Before the story has even ended properly, viewers are whisked off on the next adventure and encouraged to ignore any inconvenient plot holes that might arise from the original movie’s ending. This is a necessity since thinking too much about Back to the Future’s ostensibly happy ending makes it less cheerful and more existentially terrifying. In the movie’s ending, Marty technically arrives in a version of his life that he has never inhabited before, meaning the version of his family that he lives with are complete strangers.

Back To The Future’s Ending Was Always Bleak When You Think About It

Marty Arrives In A Totally Unfamiliar Life With No Memories

The McFly family of Back to the Future’s ending have a lot more financial comfort than the family from the start of the movie, but they don’t share any of Marty’s childhood memories, any of their existing personality quirks, or really anything in common with their alternate selves from the original version of 1985. This is a chilling prospect even before viewers consider Back to the Future’s second Marty McFly, a character whose unavoidable existence makes the original movie’s ending go from unsettling to dread-inducing.

Another version of Marty leaves for 1955 just as the movie’s hero arrives in 1985. However, he can’t actually arrive in 1955 and alter the timeline further, because this would change Marty’s current reality in the movie’s ending. Not only that, but his existence would result in him then returning to 1985, prompting a third version of Marty to leave for 1955, resulting in an endless stable loop. As such, while Marty McFly must adjust to a completely unfamiliar, alien version of his family life in Back to the Future’s ending, a darker fate is presumably in store for his alternate self.

The Fate Of The “Second Marty McFly” Makes Back To The Future’s Ending Even Darker

Marty’s Time Travel Creates A Duplicate That Must Be Dealt With

While Back to the Future’s DeLorean sometimes seems to intervene to ensure that Doc and Marty don’t alter the timeline too much, the fact that Doc hypothesized one true timeline at all is bad news for this alternate Marty. For the new, ostensibly improved version of 1985 to stay the same, the second Marty must be killed while traveling to 1955 or shortly after, so he cannot change the timeline further. Some fan theories argue that Doc accounted for this and programmed the DeLorean to doom this version of the character.

However, that seems uncharacteristically ruthless for the lovable Doc. Although he is admittedly unhinged, the movie’s supporting star never comes across as malicious. Christopher Lloyd’s Back to the Future hero even gets a love interest in the third movie, so it is tough to picture him sending a version of Marty to his certain death at the end of the original movie. There is another option, although it might be just as unlikely as Doc killing Marty to avoid creating further time travel paradoxes.

As unlikely and optimistic as it sounds, it is possible that the changes to the Back to the Future timeline only caught up with the present right at the exact second that this second version of Marty was about to go to the past. If this is the case, then the main version Marty comes back at the same moment, thus effectively closing the loop. This is the most idealistic outcome, but also the one that the original movie appears to support considering the fact that the fate of the alternate version of Marty goes unmentioned.

Was There Really A Missing Marty McFly At The End Of Back To The Future?

Marty’s Duplicate Could Be Solved By A Multiverse

Closing the loop is one explanation for how Back to the Future’s ending avoids a time travel paradox. However, this is also another possibility that has been explored in a lot of time travel fiction. If Doc Brown is wrong about the one true timeline theory and there are endless timelines existing simultaneously in a multiverse of coexisting realities, this might explain how both Martys can live. Details like Back to the Future Part II’s almanac seemingly support Doc’s thesis, but this remains a credible possibility.

If Back to the Future does take place in a multiverse, the two Martys could both exist in different parallel timelines without necessarily impacting each other’s lives. Like the theory of Marty closing the loop by arriving in 1985 at the exact right moment, this theory is somewhat hopeful. However, the fact that Marty now exists in a reality where none of his memories ever happened the way he remembers them is an unfortunately unavoidable outcome of Back to the Future’s ending.