SPOILER WARNING: This article contains major spoilers for "Legacy," the Season 5 finale of The Flash.
The Flash just said goodbye to Nora West-Allen. In "Legacy," the Season 5 finale, she started to disappear as a result of the changes Team Flash made to the timeline. Then, when Reverse-Flash proposed the Negative Speed Force as a solution, she turned it down and let the new timeline take its course.
Just as the team defeated Reverse-Flash, Nora's hands began to crack, with a blue light shining out from within. "A new timeline is setting in," Reverse-Flash revealed. "A new timeline that you created when you destroyed the dagger. I'm sorry, Little Runner, for trading you in like this, but I had to be sure that I could go free."
"You can still save her, Barry," he added. "The Negative Speed Force. She has to go there. It's the only place immune to timeline changes, but you have to go now. You have to go, Barry! Or we lose her forever. That's right. I've grown fond of her too. In many ways, she's shown me what it's like to have a daughter."
Without wasting any time, Barry and Nora ran straight into the Negative Speed Force. However, she didn't stay long. Despite her father's pleas to keep running, Nora peeled off and ran back to the team. "If I go back in, the Negative Speed Force will be a part of me forever," she sobbed.
Iris insisted they would find a way to extract it, but Nora put her foot down. "Mom, you can't. None of you can. It's making me like Thawne, full of anger and hate. I don't want that to be my legacy," she said. The blue cracks began to spread up her arms and over her torso. "This is all on me. All of it. My mistake. And I'm not going to make another one. Sometimes all you can do is live with the consequences. Thank you for everything." With that, she disappeared from the new timeline.
Before their final battle with Reverse-Flash, Nora left her parents a message in her journal. "Hi, Mom and Dad. If you're watching this, it means that something went wrong, but I don't want you guys to be sad. I'm not. I always wanted to be a hero, to use my extraordinary powers to help people," she told them. "That's why I came here: to meet my family, stop Cicada, help fix the Flash's legacy and save him from disappearing in the future. I believed I could do the impossible, but I never imagined it would turn out like this. I'm glad it did."
"I wouldn't change anything about my time with you, my sweet parents, the most important people to me in the world. I wish I could be there to celebrate every new chapter, to witness every success," she continued. "Just know, that no matter where I go in my life, you'll always be by my side. Because of you, I know I will never, ever be truly alone, and I will feel your love and support like a warm hug, comforting me, wishing me to be the best person I can be. Thank you for everything. For making me a hero, and for loving me even if I wasn't perfect. Please remember that I love you both and I always will, no matter what the future brings."
Seeing as the timeline has changed, Nora may not be born at all. After all, Barry and Iris had her before "Crisis," which now takes place this year instead of 2024. If Barry survives, though, a different version of her may exist in the future. Either way, Nora as she appeared in The Flash Season 5 has now been erased from existence.
Losing Nora wasn't the only consequence of this change to the timeline. Because of their meddling, the timing on "Crisis on Infinite Earths" -- the event that supposedly leads Flash to disappear -- has moved up. Now, the in-universe timeline will take place in 2019, which aligns with The CW's Arrowverse crossover plans.
Returning this fall on The CW, The Flash stars Grant Gustin, Candice Patton, Carlos Valdes, Danielle Panabaker, Tom Cavanaugh, Jesse L. Martin, Danielle Nicolet, Hartley Sawyer and Jessica Parker Kennedy.