Barry, Cisco and the rest of Team Flash seek out Tracy Brand - the physicist Barry's future self said would one day help him to trap Savitar in The Speed Force. Unfortunately, Killer Frost is looking for her as well, promising a battle between the former friends. Meanwhile, Joe's ponders his relationship with Cecile and how it can grow with half of his life hidden from her.
The Terminator (a future threat tries to kill the woman who is destined to bring about his downfall, name-dropped by Tracy Brand) and The Flash: Out of Time by Robert Venditti (basic idea for Savitar's identity),
As showy and impressive as it is, why did Killer Frost freeze HR's drink - a trick showing more fine control of her powers than she's ever shown before - when all it did was tip him off that she was close? (Caitlin's influence trying to warn him?)
After taking Tracy to STAR Labs, Barry asks Joe why he hasn't told Cecile about Team Flash. Given that all of the events of the episode take place in one night (we know this because Cecile says that she told Joe that she loved him that morning whens he visits him at his house later) when has Joe had time to talk to Cecile?
The chemistry between Anne Dudek and Tom Cavanagh is brilliant and salvages what might be an otherwise creepy subplot with HR hitting on a woman under severe duress.
Carlos Valdes and Tom Felton do a good job playing off of each other, exploding the underdeveloped dynamic between Cisco and Julian.
Jesse L. Martin is a treasure. Not a lot else needs to be said.
The sequence in which Barry saves Tracy Brand from Killer Frost's attack in the lab is a new high-mark for the show's excellent slow-motion effects work.
Ignoring that Killer Frost really should not be able to out-pace The Flash on ice-slides, the chase sequence looks amazing.
In this episode, Killer Frost shows the ability to create ice-slides - bridges of frozen water on which she can move at great speed. Ironically, while this ability is often utilized by ice-manipulating heroes and villains in comic books (Iceman from The X-Men being the most famous example.) no version of Killer Frost in the comics made use of this ability. This may have been due to the pre-New 52 Killer Frosts being heat-vampires rather than an ice-creating elemental. The Killer Frost in the Justice League cartoon, however, did have the ability to create ice slides.
While not creating ice-slides, the Killer Frosts in the classic comics did have the ability to fly - presumably by using cold air to provide lift or through some latent telekinetic ability that also allowed them to shape and manipulate the ice they created by draining the heat from objects.
At one point Tracy Brand compares herself to Sarah Connor in The Terminator. Cisco corrects her and says she's more like Miles Dyson. In the Terminator mythology, Miles Dyson is the scientist who creates the neural-net processor that leads to the development of Skynet - the artificial intelligence that tries to take over the world but is defeated by John Connor, son of Sarah Connor.
"Eppur si muove" is Italian for "And yet it moves." As HR notes, this statement is attributed to the astronomer Galileo who reportedly said this phrase after being forced to recant his research which proved that The Earth moved around The Sun rather than the reverse, which was the accepted dogma of the Roman Catholic Church at the time. Since then, the phrase has become a rallying cry for scientists whose research is held back or decried by political or religious pressure.
Tracy theorizes that Savitar's armor is made of a theoretical substance capable of dispersing heat at high temperatures. This sounds remarkably similar to how - in the modern The Flash comics - Wally West was able to create a costume of pure Speed Force through sheer force of will to protect him from the effects of friction and static build-up.
The concept of Barry Allen having to fight a future corrupted version of himself lies at the center of the New 52 Flash story Out Of Time.
Tracy Brand's dissertation was on the purely suppositional nature of extra-dimensional energy. Barry tells her - not realizing she hasn't talked with anyone about her hypothesis yet - that her work on relativistic quantum mechanics and its application to interspatial theory to manipulate matter on a sub-atomic level is groundbreaking.
Barry is able to use a spark of his speed lightning to ignite a gas torch as a weapon against Killer Frost.
Tracy Brand's theories of quantum mechanics involve ideas of wave-particle duality, quantization of energy and time- symmetric formulation of quantum theory and how the boundary conditions lead to principle causality and the psychological arrow of time.
Tracy Brand studied speedsters and theorized the idea of The Speed Force's existence based on the energy produced by a speedster in motion being more than they could generate through sheer kinetics. She theorizes this energy could be manipulated or controlled... perhaps even turned into a prison of sorts.
Barry's costume is made of vulcanized Teflon. It neutralizes any electron imbalance and prevents the friction of Barry's movements from generating a lethal dose of static charge.
"Eppur si muove" is Italian for "And yet it moves."
Tracy Brand notes that the way light reflects off of Savitar's armor is unlike any metallic compound she's ever seen.
In Fermi liquid theory, any sort of non-Fermi liquid is called "strange metal". This is a theoretical compound capable of dispersing heat at high temperatures.
Tracy theorizes that Savitar moves so fast that he needs his armor - which is made of this "strange metal" to neutralize the charge that builds up around him. This seems to be like Barry's vulcanized Teflon costume, but on a much larger scale.
Tracy further theorizes that without the suit, Savitar would just be a man with a major case of static cling. She also guesses that Savitar's own velocity could be used against him with the right device and he could be trapped in The Speed Force.
HR: So our hopes of defeating an evil speed god hinge on a grad student?
HR: ... could be worse.
(The window in the door of Tracy Brand's lab ices over and shatters. Killer Frost enters.)
Killer Frost: Admission here is so easy.
(Barry has been knocked down by one of Killer Frost's blasts. Cisco nervously approaches her.)
Cisco: So... you've gone full-on Killer Frost, huh? New threads and everything.
Killer Frost: No more pencil-skirts for me.
Cisco: (raising his hands defensively) I don't want to hurt you.
Killer Frost: You won't. But I will hurt her.
Tracy:You're interested in my theories on quantum mechanics?
HR: Your ideas of wave-particle duality. Your quantization of energy. And your time-symmetric formulation of quantum theory. And -
(Cut to the STAR Labs portable lab van, where Cisco and Julian are manning the station. Cisco is talking into a walkie-talkie.)
Cisco: - how the boundary conditions lead to principle causality and the psychological arrow of time.
HR: ... and the psychological arrow of time.
Tracy: You really know your stuff!
HR: Well... je suis... smart.
Cisco: (over HR's ear-piece) Lay off the French. And lay off the improv too, please?
(Team Flash explains to Tracy why Killer Frost is trying to kill her.)
Joe: We know it's a lot to take in.
Tracy: Well, to be fair you're basically telling me I'm Sarah Connor in Terminator.
Everyone Except Tracy: Wellll...
Cisco: More like Miles Dyson.
Julian: Caitlin could be home now. Had you stopped her, she would be here. But you didn't! You couldn't! Tell me why!
Cisco: Because I'm afraid!
Julian: Afraid of what?!
Cisco: Afraid of killing her! (holding up his hands) I'm walking around with two loaded guns here, ready to go off. I mean, what if she's hurting Barry or Joe or you? And I have to save you and I can't control my powers and I end up killing her?! She's my best friend. And I rather it be me than her.
Tracy: How did you know I was here?
HR: (clears throat) I may have done a bit of holographic stalking. I stalked you. Holographically.
Tracy: You mean, in the future, I'm still obsessed with a 500 year old Italian polymath?
HR: (laughs) It would appear so.
The Flash: I know who you are.
Savitar: It's about time.
The Flash: Yes, it is. Everything with you is about time, isn't it? The past? The present? The future? You know all of it, right? And you know everything about me! About Joe! About Wally! And Iris?! You know our strengths. You know our fears. You know how much we love each other. And you know how to use that love against us. All this time we thought we couldn't stop you because you were one step ahead. But that's not it! You don't just know what's going to happen to us. You were there. You lived it. You remember... when you were me!
(Savitar kneels down and his armor begins to unfold. Out of it steps a somewhat familiar figure. The hair is longer and dirtier and the face is scarred... but it's clearly Barry Allen)
Savitar: Like I told you.from the beginning.. I am the Future Flash.
According to the data from Future Barry, Tracy Brand will win the 2021 Nobel Prize, The Copley Medal and a Presidential commendation.
In 2021, Tracy Brand develops the technology that traps Savitar in The Speed Force.
During the events of this episode, Wally is on Earth Three visiting Jesse Quick.
In 2017, Tracy Brand is a graduate student enrolled in Central City University's theoretical physics program. She failed her dissertation and is in the process of burning her notes when Barry, Cisco and HR find her.
On Earth 19, the great physicist Einstein's first name was Norbert. Not Albert.
On Earth 19, the fried potato snack Americans call Fries and the British are Chips are called Finger Chips.
HR's drink of choice at CC Jitter's is a triple-shot no-whip mocha Flash.
Tracy Brand's drink of choice is on the CC Jitter's secret menu. It is called The Zoom - triple espresso with a shot of cayenne.
Team Flash wipes the security footage at Central City University to protect Caitlin's identity.
Team Flash tells Tracy Brand about her future and that her theories regarding The Speed Force are right.
HR claims to have written a book of motivational speeches on Earth 19 - All's Wells That Ends Wells.
The Galileo of Earth 19 also coined the phrase"Eppur si muove".
HR is familar with the writings of Galileo and knew that there is a statue of him in one of Central City's parks. It is because of this that he recognizes the landmark in one of Tracy's photos from the future.
Joe dumps Cecile just before she is taken hostage by Killer Frost.
Killer Frost is able to repeat the exact words Barry is going to use as he tries to talk sense into her. She claims this is because Savitar knows what Barry did in his past and told her what Barry said.
Savitar tells Barry that the time of his ascension is almost about to happen.
Cisco takes a blood sample of Killer Frost while she's fully mutated. Julian thinks he can use that to reverse engineer a permanent cure for her condition.
The team notes that Savitar rescued Caitlin rather than kill Tracy Brand, indicating that he needs Caitlin for something.
Joe takes off his wedding ring and tells Cecile that he loves her, promising there will be no more secrets between them. We later learn that he told Cecile about Barry and Wally's secret identities and his work at STAR Labs.
Barry figures out that Savitar is a corrupted future version of himself.
We don't get to see HR's talk with Tracy and how he convinces her to try and help Team Flash build a speed trap for Savitar.
The Bottom Line
Flawless. Absolutely flawless.