Tonight's episode -- "I Know Who You Are" -- carried with it the revelation fans of "The Flash" have been waiting for all season -- the true identity of Savitar. His unmasking will change everything for Team Flash in upcoming episodes because Savitar's identity will affect each of them on a dark, personal level. The revealing of his identity also explains why Caitlin was so willing to trust him last week, why she was so quick to do his bidding. Her transformation into Killer Frost took another turn this week, as Savitar had her hunt down genius physicist Tracy Brand. Tracy is the only person who can trap Savitar in the speedforce, so both Team Flash and Team Savitar were after her this week. Joe West also took his relationship with Cecile to the next level after she said "I love you" and he got permission from Barry to tell her about The Flash and Kid Flash. Tonight's episode really challenged a lot of relationships, especially Caitlin and Cisco's, as Cisco was pushed to the brink and forced to use his powers against her. With only three episodes left after tonight, Barry and the team are really going to have to think outside the box to trap Savitar, especially now that they know the terrifying truth about his identity.

Future Genius

The Flash Tracy Brand

Tonight's episode introduced Tracy Brand ("Covert Affairs" alum Anne Dudek.) Tracy was studying theoretical physics in school when Barry, H.R., and Cisco went to find her. According to Future Barry, Tracy was the one who developed the technology to trap Savitar in the speedforce in the future. When Barry, Cisco, and H.R. caught up with her she was burning her research and ready to throw in the science towel. Tracy's dissertation had been rejected and she was ready to give it all up. Killer Frost arrived to intercept her too, so Team Flash had to save Tracy from Caitlin's icy blasts.

H.R. then tried to talk to Tracy about her speedforce theories at Jitters later, but Caitlin showed up again. It wasn't until Tracy was shown the information about her future that she warmed to the idea of working with the team. According to Tracy, she had started studying speedsters and began developing theories about the energy that their suits release. She also had a theory that the energy coming off of their bodies was also a part of something else -- something unnamed (the speedforce) -- that could be manipulated or controlled. Tracy agreed to help the team, but when Caitlin kidnapped Joe's girlfriend Cecile, Tracy had to become bait.

Not Yet a Killer Frost

The Flash Killer Frost

The action in this episode came not from Savitar, but from Caitlin, who was on a mission to kill Tracy before Tracy could built her speedforce trap. Caitlin was thwarted by Team Flash three times. First, Barry was able to use fire to deflect her at Tracy's university. Then, when Caitlin came to hurt Tracy at Jitters, Barry was able to lead her all over the city and away from Tracy. This sequence was quite incredible, as Caitlin surfed her way around Central City on ramps she created out of pure ice. Cisco could have taken her out during this chase, but he hesitated and Caitlin blasted him. Team Flash tried to stop Caitlin again while she was holding Cecile hostage. Cisco was waiting in the wings for his chance to vibe her, but she knew where he was. Cisco did vibe blast her though, in time to take a sample of her blood. Savitar rushed in a saved her, which thankfully meant both Cecile and Tracy were safe.

The transformation of Killer Frost in this episode was fascinating, especially since the newest character on the show this week was a female scientist. Usually Caitlin would have been the person to talk to Tracy about being a scientist in the future, but because Caitlin wasn't working with Team Flash this week, H.R. had to talk to Tracy. Their moments together were very sweet and it's possible we'll see a budding romance develop between those two. Hopefully Tracy isn't Caitlin's "female scientist" replacement because "The Flash" would not be the same without actress Danielle Panabaker.

Caitlin was also challenged by Savitar a lot during this episode. He taunted her for not having killed anyone yet, for not living up to her name sake. Even when Caitlin had the chance to kill, she couldn't do it. The same way that Cisco was wielding his powers for good, there is clearly still good in Caitlin. Will she go full dark, no stars if she does take someone's life in upcoming episodes? Can Julian synthesize a cure for her? Should she be cured? There are so many unanswered questions regarding Caitlin's powers and why they make her evil. Hopefully she can be redeemed by the end of the season because the show really isn't "The Flash" without Caitlin Snow.

I Know Who You Are

The Flash Barry Allen

The biggest twist in the episode came from the final reveal: the identity of Savitar. For months Savitar has taunted Barry in his menacing blue, metal suit. He has created multiple metas in Central City, he gave Wally speedster powers, he raised up a cult, he calls himself the God of Speed -- he truly is a terrifying figure. We know that in the future, he not only kills Iris but also damages Wally so bad Wally ended up paralyzed. So, who is Savitar? Savitar is a future version of Barry Allen. ZING. A lot of people called this, including CBR's own Meagan Damore, who theorized about it back in March.

So, Barry Allen. What does that even mean? Why on Earth would Barry want to raise up an army of meta humans and kill Iris? Clearly this version of Barry is insane, because there are no logical reasons for him to do these terrible things. What will this reveal to do to current timeline Barry? Worse yet, what will it do to Iris? How will she be able to handle learning that the man who loves her will one day grow into a man capable of killing her? Right now there are very few answers to be explored, because the reveal came at the end of the episode. Hopefully the final three episodes reveal what drove Future Barry to such madness that he would kill the love of his life. While it may be an interesting plot twist to make Barry both hero and villain, this whole situation needs to be resolved quickly, because no one wants to see Barry become a killer.

Cause and Effect

During next week’s episode -- “Cause and Effect” -- Barry will deal with the repercussions of discovering Savitar’s true identity. As you can see in the above trailer, Cisco’s attempts to change Barry’s memories get a bit out of hand as Barry suffers temporary amnesia.

DRASTIC TIMES CALL FOR DRASTIC MEASURES – Barry (Grant Gustin) takes drastic measures to stop Savitar. Meanwhile, H.R. (Tom Cavanagh) continues to push Tracy Brand (guest star Anne Dudek) to design the trap for Savitar and Killer Frost (Danielle Panabaker) returns with an interesting proposal. David McWhirter directed the episode written by Judalina Neira & Lauren Certo. Original airdate 5/9/2017.

Starring Grant Gustin as the Scarlet Speedster, “The Flash” airs Tuesdays at 8 pm ET/PT on The CW. The series also stars Jesse L. Martin, Tom Cavanagh, Carlos Valdes, Candice Patton, Danielle Panabaker, Keiynan Lonsdale and more.