The Season 4 finale of The Flash packed a bunch of potentially exciting mysteries right into the tail end of the episode, although arguably its biggest came right in the middle. In the midst of Team Flash attempting to project Barry into The Thinker's mind via the in-labor Cecile, the psychic meta snapped and purposefully announced: "I found Thomas; he's been this way all the time." We've been wracking our brains ever since the moment trying to figure out who was controlling Cecile, who Thomas is, and what that all may mean. Here's the best we've got so far:
Thomas Is Caitlin Snow's Father
Thomas is Caitlin Snow's believed-to-be-deceased father, although that message seems to say he's not as dead as we all assumed. Caitlin's dad, who was never given a name, is believed to have passed after losing a battle against multiple sclerosis when Caitlin was younger. Snow seemed to react with shock to the news delivered by Cecile's weird voice, which leads us to believe that she recognized the name Thomas and was startled by the fact that he was found. The question is, who would care about this enough to try and alert Caitlin Snow?
Remember how Cecile had the ability to take on personalities and read others thoughts late in her pregnancy? Good. Now, remember that Killer Frost is somewhere deep within Caitlin but unable to come out and communicate with her other self? Finally, remember that whole bit where Caitlin remembered a repressed memory where she was Killer Frost as a child? The Flash just opened up a can of worms with that moment that could mean there are gaps of Caitlin's childhood she almost certainly doesn't remember. This would explain how her father may still be alive without Caitlin knowing it, although we have no clue how Killer Frost managed to find him while trapped away inside her body.
Thomas Is Caitlin Snow's Brother
Caitlin Snow is still contacted by Killer Frost in this theory, although her message about Thomas is not referring to daddy dearest. Instead, Killer Frost is alerting her other self to the fact that she found their brother, and also that he's been "this way all the time." We'll tackle that latter part in a bit, but first, why would anyone who watches The Flash think Caitlin Snow has a brother?
Remember Earth-2 Killer Frost? She had a brother named Charlie who died and began the cycle of events that led to that Caitlin becoming Killer Frost. Seeing as Earth-2 Caitlin had a brother, is it so crazy to think that Earth-1 Caitlin has one as well? Sort of, considering The Flash has never mentioned or alluded to Snow having a mystery brother, although other shows have managed to pull off similar plot points. Should Caitlin have a brother named Thomas, he may be a meta like her, which might explain why he's always been a certain way. That would explain the second sentence of the quote, but once again, we have no clue how Frost would've found anyone in her current state.
It's Thomas Wayne, THE Thomas Wayne
The Arrow-verse will introduce Batwoman in a crossover in the 2018-2019 TV season, and The CW president Mark Pedowitz confirmed that Gotham City will be added to the map of locations relevant to all the shows. Arrow revealed earlier in Season 6 that Bruce Wayne exists in the Arrow-verse, which could mean that The Flash intends to explore another member of the Wayne family in Season 5 in a nod to the Flashpoint story in DC Comics, which features a Thomas Wayne who became Batman after his son Bruce was gunned down. The Flash skipped over a lot of the comic Flashpoint elements when it did its own Flashpoint story; perhaps Season 5 will see the show exploring that comic arc in-depth with Thomas Wayne on board.
Of course, there's some tricky stuff that would need to be explained for this to happen. Could this be a result of Nora West-Allen's own Flashpoint and a nod to the comic Flashpoint in which Bruce Wayne died and Thomas eventually became Batman? Could a Thomas Wayne from another Earth in the multiverse have a part to play? We're getting a little too far ahead of ourselves here, but a mystery person possessing Cecile and delivering this info makes a little more sense than the Killer Frost theory at present.
Thomas Is Another Entity Living Inside Caitlin
Killer Frost is unable to leave or take over Caitlin's body, which really complicates the theory she is the voice that overtook Cecile. It's going to be hard for Frost to find anything locked away inside Caitlin's mind, unless of course, she found something else locked in there with her. What if Killer Frost isn't the only entity existing within Caitlin, and she has another person in there named Thomas?
This theory explains why Caitlin was shocked, how Killer Frost was able to find someone, and perhaps how they may both know how he's always been. Perhaps Thomas is responsible for Caitlin's inability to bring Frost back out of hiding, and is keeping her captive in some way? That has the potential for a very interesting story arc for Caitlin Snow in The Flash Season 5, which is something a lot of fans would like to see. Should this be a war for Caitlin's mind, we've already seen Barry can enter people's heads and help them out with his powers. Will he have to invade Caitlin's brain to save Killer Frost in Season 5?
Thomas Is Someone From The Future
Nora West-Allen re-opened the whole time-travel element on The Flash when she came from the future for a currently unknown reason, so could Thomas possibly be from the future as well? If that's the case, why was whoever it was that possessed Cecile so dead set on delivering that message to Caitlin and Joe? Perhaps the person who sent the message didn't really have the option to deliver the message to Nora, as that person wasn't yet born!
Yes, perhaps it was the baby who was trying to send a message about Thomas. Marlize revealed that Cecile would no longer have her psychic abilities upon delivering her baby, which leads us to believe she and Joe's new baby was the psychic metahuman all along. Fast forward 30 years into the future, it's possible this psychic meta is part of Nora West-Allen's Team Flash and attempting to relay a message throughout time through her past self to her speedster niece. Joe and Caitlin may remember what Cecile said because it's so bizarre, and then recall it when the name Thomas gets brought up again. Nora fills everyone in on the whole backstory of Thomas and why he's important, and maybe Barry travels to the future to meet the adult version of Joe and Cecile's baby? It's weird, but so are most plotlines that involve time travel.
The identity of Thomas will presumably be revealed this fall when The Flash returns to The CW on Tuesdays at 8:00 p.m. ET. Those needing a good superhero show to binge while waiting for that will find all available options at our superhero premiere guide. For everything else new coming to television in the near future, visit our summer premiere guide.