We start the season right where we left off, in Joe Wests living room meeting Nora West Allen, future daughter of Iris and Barry Allen. As the group tries to grapple with the reality of her existance, Nora explains she's from 30 years in the future, also a fellow speedster, and goes by the name of XS, since she's always doing things in "excess" (get it?), like jumping in and helping Barry destory the Star Labs satelite in order to defeat Devoe.
From there we move to Star Labs where we watch Barry and Iris grapple with the existance of Nora and what effect her time traveling may have on the future timeline. As the group tries to figure out a way to send Nora home where she belongs, a shot on the TV shows a meta human attacking a local jewelers nearby.
When Barry heads off to face the meta (named Gridlock), Nora ends up secreatly tags along and ruins Barry's plan, not only allowing Gridlock to get away, but supposedly tainting herself with his dark matter, forcing her speed to slow and trapping her in the past.
Meanwhile Ralph has a hard time dealing with his newfound knowledge of time travel, and Iris realizes that she and her daughter aren't as closely bonded as she had hoped (and that inflation will cause coffee to spike about $40 by 2040.) Cisco nurses a hardcore hangover/broken heart combo.
Once back at Star Labs, Iris and Barry come to terms with the "new normal" of their family dynamic, and Barry puts the pieces together that Nora may not exactly be here against her will. After confronting her, Nora admits she ran from the future voluntarily, in hopes to save her father from what will be his eventual and immenant dissapearance.
While Nora reveals secrets about her fathers future, Caitlin learns about her own fathers secret past, when Ralph figures out that the certificate signed after his death is fake, and he may be connected to Caitlin's mysterious meta powers.
The shows last act rounds itself out in classic Flash fashion with the Team coming together to figure out how they can save a falling plane Gridlock has planned on crashing. They use the phasing power of all three speedsters (Hi, Wally!) to help it land safely, highlighting Barrys deep bond with Nora as he teaches her how to phase for the first time by repeating the speech Wells once gave him, seasons prior.
It all seems like the episode is going to wrap up in a warm fuzzy fashion with Nora sticking around for awhile (and Barry keeping his impending dissapearance a secret from Iris), but the tag before the credits roll gives us a glimpse into this seasons true Big Bad: a slithery looking, masked Chris Klien who hunts down Gridlock (now being taken to Iron Heights in custody) and declares that he is on a mission to kill every last meta in Central City.