Spoilers for anyone who hasn't yet watched The Flash's penultimate Season 4 episode.
When The Flash introduces new superpowered heroes and villains, certain things have almost always been clear: a particle accelerator explosion occurred, or Barry was zapped out of the Speed Force, or some other dark matter-infused event. But after the bonkers reveal in "Think Fast," much of what we knew about meta humans may have been turned upside-down, as we learned that Caitlin Snow has had her Killer Frost powers ever since she was a kid. And that twist could very well be the most interesting and shocking reveal we've seen on The Flash this season. So let's question what it all might mean.
How did Caitlin get her powers, then? That's the bazillion dollar question right now, since there aren't any major signs for what the cause might be. The biggest clue we have lies in Caitlin's formerly repressed memories, in which she'd fallen off of a bike and was nearly hit by a truck, all while a man (presumably her father?) shouted her name. In the second look at that memory, we saw the Kid Killer Frost reveal, though any and all details surrounding those moments are unavailable. No dark matter to be seen, which might not even be important in Caitlin's case. Which leads us to the connected question...
When did Caitlin first get her powers? Since Caitlin clearly didn't have any recollection of having Killer Frost abilities prior to Savitar's arrival, it's both feasible that she's had the power since birth and that she had just gained it right in the seconds after her bike accident. The Flash hasn't introduced any characters proven to have been meta humans since birth, though there's a pretty big chance that Caitlin's science-practicing parents were responsible, especially if it was indeed her father whose voice viewers heard. (I've got a back-pocket theory that this event is tied to the timing of Nora's murder and Flashpoint, but it requires multiple coincidences.)
How did Caitlin lose her Killer Frost powers? Also a hard one to pinpoint for now, since we have no idea what happened after the crash. If Caitlin let Killer Frost loose one some random person, possibly killing them, then I would bet all my money on the elder Snow generation genetically or mentally manipulating the young girl into forgetting it, and then stopping her from being able to automatically conjure her icy personality. Considering how little we know about this family, it's also entirely possible that Killer Frost lived up to her yet-to-be-conceived name by being responsible for the death of Caitlin's father. She would have had every reason to voluntarily repress the ability if that were the case.
Does Caitlin's reveal have anything to do with Cecile's situation? Before we learned about Caitlin's long history with Killer Snow, Cecile was the first character who formed otherwise unexplainable powers in the core group. She's now the latest to experience updated changes, too; where she could once read people's minds, she can now absorb their personalities, which has potentially strange implications for the baby growing inside her. (And it would all seem overly silly if Danielle Nicolet wasn't so naturally enjoyable.) So could Caitlin's situation have anything to do with whatever changed Cecile's chemical makeup?
What does this mean for Mystery Girl's reveal? Similar to Cecile, Mystery Girl's metahuman existence now seems primed to connect to how Killer Frost came into being. That could still all get explained away with time travel and/or another Earth, but I'm currently more invested in discovering how Mystery Girl's bloodline and Caitlin's bloodline compare, as far as where their powers came from. Because if Killer Frost actually was birthed from science that doesn't require dark matter, then it's possible that's how Mystery Girl gained her super-speed, or even [literally a billion other story points].
How will Killer Frost help take down The Thinker? Considering all this is happening right when The Thinker's Enlightenment scheme is going down (or up), it seems very likely that Caitlin will regain control of Killer Frost for at least as long as it takes to help Team Flash bring DeVoe's reign of preconceived terror to an end. Of course, because this is The Flash, it seems just as likely that Caitlin might go on a retreat to "find herself: when the finale starts, only to become a series regular on Arrow Season 7. But hopefully we'll just see Thinker's satellites getting blasted by ice blasts.
The Flash has just one episode left to show us how all these plot strands come together, and the finale will air on The CW on Tuesday, May 22, at 8:00 p.m. ET. To see when all the other big shows are ending, head to our season finale rundown, and then check out our summer premiere schedule to see all the new and returning