Spoilers ahead for Episode 19 of The Flash Season 5, called "Snow Pack."
Season 5 of The Flash has been packed with West-Allen family drama thanks to Nora's prolonged stay in the past to hang with her parents, and her parents being cool with it... until last week's episode, when Barry learned that his daughter was working with Reverse-Flash in the future. Barry snapped and raced her back to her own time in 2049, ordering her to stay there and not even bother trying to return, because he would sense it in the Speed Force.
Unsurprisingly, Nora didn't just decide to follow her dad's orders, resume her life in 2049, and/or speed over to the remnants of Star City for an Arrow spinoff crossover. In fact, she did the precise opposite of what he would have wanted and went to Reverse-Flash for help figuring out how to get back to 2019 without Barry realizing she had raced through the Speed Force to get there. Reverse-Flash knew of a way and trained Nora in how to do it, and in doing so, he may have created the next big Flash villain... or villains.
Reverse-Flash introduced Nora to the concept of the Negative Speed Force, which fans of DC Comics may have recognized from the "Rebirth" mythology. Nora realized that Reverse-Flash has been able to travel back and forth in the timeline and from place to place without other speedsters sensing it, and apparently, this was not a plot hole or a convenience for the sake of a "Gotcha!" twist. There's a reason why Reverse-Flash can pull it off.
As the reverse of The Flash, Reverse-Flash created his own Speed Force to be able to use his speed without alerting others to his presence. Speedsters would need to tap into their darker feelings and impulses to access the Negative Speed Force, which can in turn corrupt the speedsters as well as send them zooming through time and across distance.
Nora was unsuccessful at tapping in to the Negative Speed Force for most of the episode, but in one final attempt, she experienced a flare of anger toward her parents that resulted in her bonding with the Negative Speed Force and being corrupted, glowing red eyes and everything. Nora seems to have gone full villain thanks to Reverse-Flash.
In a twist that was very unexpected for those of us who have been expecting Thawne to do something like turn Nora from the light due to his scheming and machinations, he apparently villainized Nora by accident.
After traveling back in time herself and seeing Reverse-Flash interacting with Nora, Iris came to an unsettling realization: the only person who looks at Nora like Reverse-Flash looks at Nora is Barry. Reverse-Flash feeling paternal toward Nora? I bet Barry takes that just wonderfully if he witnesses it in person.
The trailer for the next episode reveals Nora teaming up with a bunch of rogues and sporting a new look of her own, but that doesn't mean that she'll stay a baddie in the long run. Nora's turn as a villain could be little more than a one-off that teaches her a valuable lesson. We'll have to wait and see on that front.
Even if Nora is one-and-done as a villain, the reveal of the Negative Speed Force has the potential to create future big bads for Team Flash. In fact, considering that both were introduced as existing in Season 5, I have to wonder if the Negative Speed Force will be connected to the emergence of the Red Death down the line.
Or what about the "Crisis on Infinite Earths" crossover? The Flash may have recently revealed the first footage from that crossover, and I'd be surprised if Reverse-Flash didn't have a part to play in that. And how else than by using the Negative Speed Force, perhaps creating more baddies in the process?
We'll have to wait and see. Tune in to The CW on Tuesdays at 8 p.m. ET for new episodes of The Flash.