SPOILER WARNING: The following article contains major spoilers for "The Flash" Season 3. Read at your own risk!

In the Season 2 finale of "The Flash," Barry Allen (Grant Gustin) did something drastic: he traveled back in time to the moment that his mother was murdered and prevented her death. That one moment, the moment that sent his father to jail and put Allen in the care of Joe West, was averted, thus completely changing the timeline around him.

We didn't get to see how the effects of that impulsive decision played out in the finale, but -- as revealed during a press event for the show at Comic-Con International in San Diego -- it will result in plenty of changes to the CW series when it returns this October.

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A new timeline has been created, referred to as Flashpoint. Barry Allen will remember his old life, but everyone around him will have changed. Pretty much every character will find themselves exploring new dynamics and emotional arcs -- and there will even be a new Flash, played by Keiynan Lonsdale. Here's a quick list of some of the big changes in store for "The Flash" as they enter Flashpoint.

• The fallout of "Flash's" second season finale, referred to as Flashpoint, will have an effect on the other shared universe CW/DC shows. "Flash" lead Grant Gustin even said that he knows of a Flashpoint change in "Arrow," which he said was a subtle one.
• When we pick up with "The Flash" in the season three premiere, a year will have passed since Barry altered the timeline and he will be loving his new life. Both of his parents are alive, Wally West is the Flash, and Barry works for the CCPD. But Barry will also get advice from another speedster about navigating the new timeline, Gustin said.
• Keiynan Lonsdale spoke about his role as the Flash of the Flashpoint timeline, saying that he's confident in the part -- maybe too confident. But, as Jesse L. Martin revealed, his identity won't be known to his father, Joe West.
• Joe West will be on the outs with his daughter Iris West (Candice Patton) because of unrevealed reasons. Patton confirmed that Iris is still a reporter in the Flashpoint timeline, which is a job that she loves portraying on screen. Martin said that his character will be at a low point, and Barry will have to work hard to get Joe out of his rut. Lonsdale and Patton both weren't sure if Joe West was still married in the Flashpoint timeline, as that hasn't come up yet in the scripts they've received. Overall, though, the West family dynamic will have changed.
• Joe West's relationship with the rest of the cast will have changed as well. While he will interact with Kid Flash, he won't know that the hero is his son, Wally. And since he didn't raise Barry Allen, the two won't be terribly close -- therefore, Joe won't know who Cisco (Carlos Valdes) or Caitlin (Danielle Panabaker) are.
• Carlos Valdes spoke about Cisco's arc in the upcoming season, saying that Flashpoint will affect the entire dynamic of the show. And while he remained mum about exactly how his Vibe powers will factor into his new Flashpoint role, he did tease that powers have a tendency to grow alongside characters.
• New cast addition Tom Felton spoke about his character, fellow Central City Police CSI Julian Dorn, saying that he will be suspicious of Barry Allen and will have a "slightly abrasive" relationship with him. He also said that while Julian will know Barry through years of working together, Barry will not be familiar with Julian due to his newness in the Flashpoint timeline.
• With "Supergirl" now on the CW, Grant Gustin expressed great excitement at the thought of Superman coming to the series (played by Tyler Hoechlin). But don't expect to see a Flash and Superman team-up anytime soon. Gustin revealed that he has not yet shared a scene with Hoechlin, and doesn't know if he actually will. "The Flash" is in production on the second episode of Season 3 right now, and "Supergirl" begins production on its second season next week.
• And while it's been established that all four of the CW's DC shows ("Arrow," "Flash," "Supergirl" and "Legends of Tomorrow") will have a weeklong crossover this season, none of the cast members yet know what it will entail. When asked what he would like to see happen in the crossover, Keiynan Lonsdale laughed and said he just hopes he's in it.

Starring Grant Gustin, Jesse L. Martin, Carlos Valdes and more, "The Flash" returns to The CW on October 4 at 8 pm EST.