[Warning: major spoilers for The Flash Season 2 finale, "The Race of His Life," lie ahead.]
After losing his father Henry Allen at the hands of Zoom, a devastated Barry decided to travel back in time to stop the Reverse-Flash from killing his mother Nora. He achieved his goal and watched as the Season 1 finale Flash, who attempted to do the same thing in last year's season finale, disappeared. How will Barry's decision impact the current Flash timeline? Enter Flashpoint.
Flashpoint is a five-issue DC Comics series written by Geoff Johns, an executive producer on The Flash and newly appointed head of DC Films, and featuring art by Andy Kubert. While I recommend picking yourself up a copy of the incredible story, here's the basic premise: Barry Allen finds himself in an alternate timeline in which his mother is no longer dead. More importantly, in this alternate universe, most of the nation's heroes don't exist -- there's no Superman or The Flash; Wonder Woman and Aquaman are at war; Batman is Thomas Wayne, driven to the edge after the murder of his son Bruce in Crime Alley. Oh, and Captain Cold is now a Central City hero named Citizen Cold.
With the world hanging in the balance as the war between Atlantis and Themyscira escalates, Barry is the only person who can remember a pre-Flashpoint world, which means it's up to him to fix it. (But first, he needs his powers back.)
So how does this tie into Barry's actions in the Season 2 finale? In Flashpoint, it's eventually revealed by the Reverse-Flash that Barry himself altered the timeline by going back to save his mom -- which is exactly what Barry did in "The Race of His Life."
Barry's decision to save Nora will have tremendous consequences for Barry and Team Flash. For starters, it looks like there might not even be a Flash anymore. When Season 1 Barry disappeared in the episode's final moments, that was a sign of the changes to come. As for Team Flash, well, they're probably not even a thing anymore -- and neither are Barry and Iris. If Barry had never been adopted by Joe West, then Iris and Barry didn't grow up together.
Most of the heroes who play huge parts in Flashpoint don’t actually exist in the Arrowverse. Superman, Batman, Wonder Woman, Aquaman, and Cyborg all belong to DC Films, so the story would obviously change quite a bit to adapt. I also have a hard time believing The Flash would go quite as dark and nihilistic as the comics. That being said, it could also give other DC heroes a chance to make their debut on the CW series.
Think of this as Barry hitting the reset button. Characters from Seasons 1 and 2, like Harrison Wells, Eddie Thawne, Captain Cold, and Ronnie Raymond might all be in play for Season 3. And let's not forget the entire Arrowverse is susceptible to Barry's decision. Earlier this season, The Flash revealed that Robert Queen was The Arrow on Earth-Two, instead of his son Oliver Queen. Could Robert take the place of Thomas Wayne in Season 3? It's entirely possible.
Sure, it's possible that Arrow, DC's Legends of Tomorrow, and Supergirl could continue without any direct effect from Barry's timeline shift, given the fact that they operate in a different timeline altogether. In fact, we know Supergirl is part of an entirely different world. However, it seems likely that there will be repercussions for the Arrowverse at large. (Black Canary, anyone?)
Plus, with CW's chief Mark Pedowitz promising the network's most epic DC heroes crossover event ever in December, Flashpoint is the perfect plot device to get everyone together. And it could even explain Supergirl's entrance into the Arrowverse.
Either way. expect things to get very messy and extremely complicated.