Much to the horror of everyone, Eobard Thawne returns to Central City. But defeating him might not be so easy.
- Antagonist Title: The episode is named after Barry's ultimate Arch-Enemy and the Season 1 Big Bad.
- Arc Number: "52" once again pops up. For the matter, the season's fascination with duality and second chances (2) also comes into play this episode.
- Badass Bookworm: Barry finally gets the drop on Thawne, by using his brain as well as his speed.
- Bait-and-Switch: Cisco's Psychic Nosebleed is at first implied to be because of the goggles Harry made to harness his powers being a Deadly Upgrade for him. Turns out not to be the case.
- Because Destiny Says So: Thawne became a villain because he found out that he was destined to become a villain.
- Being Good Sucks: Barry has to let Thawne go to preserve the time line.
- Break Her Heart to Save Her: Barry drives Patty away, because he's sick and tired of evil speedsters taking his loved ones from him.
- Brick Joke: A season later, and Cisco is still trying to figure out how to put a Flash suit in a ring. Made funnier by how Cisco would ask Thawne the same thing later--earlier--whatever.
- The Bus Came Back: Dr. McGee returns after last appearing in this season's fourth episode. Ditto Francine West. Most importantly, the episode deals the return of Eobard Thawne.
- Call-Back:
- The time vault and the (original/main) Reverse-Flash costume appears in this episode.
- Iris opens up about Eddie's death to Wally in order for the latter to forgive their mother.
- Barry sends Eobard back to the future by running around the Particle Accelerator, just like how he time traveled in the Season 1 finale.
- Thawne's Kubrick Stare at Earth-2 Wells (and asking him who he is) as he's let out of the cell is callback to Season 1, which Thawne spent most of impersonating Wells. Also doubles as a Call-Forward since, from Thawne's POV, this hasn't happened yet.
- Barry phases through the wall of the building to rescue Dr. McGee.
- Can't Kill You, Still Need You: Barry is content to let Thawne rot in the Pipeline, only to discover that he needs to let him play out his history or else the timeline will implode.
- Chekhov's Gag: Harry eventually snaps at the rest of the Team simply because they labeled their Earth as Earth-1 and his Earth as Earth-2 when the reverse can also be true for anyone from Earth-2. Later revelations in Season 2 note reveal that the team may have indeed screwed the numbers up and are not actually following the same designations as the comics were.
- Continuity Nod
- Barry thinks Caitlin's worried about Dr. McGee getting kidnapped, a reference to Caitlin's tenure at Mercury Labs between Seasons 1 and 2.
- McGee reminisces about the last time her tachyon device was stolen.
- Thawne threatens Dr. McGee about fixing the tachyon device with one single word: "Learn." Well, at least we know one thing Grodd's "inherited" from his father.
- Barry and Patty's farewell on the train is basically a Dark Reprise of Barry and Felicity's goodbyes during an early episode of Season 1.
- Curb-Stomp Battle: Barry's beatdown of Thawne is so brutal that Joe was actually worried he was going to beat him to death.
- Dead Person Impersonation: Harry again impersonates Thawne, although this time is to scare Cisco and cause the fear that would awaken his powers.
- Deadly Nosebleed: Poor Cisco's first clue that something has gone awry.
- Decomposite Character: Jay Garrick's Earth-1 counterpart is revealed to be Hunter Zolomon, Zoom's civilian identity in the comics.
- Deducing the Secret Identity: After Barry acts strangely towards Patty, she goes over Barry's old case files and realizes all the ones that involve the Flash saving the day include details that Barry couldn't have known unless he was the Flash. After Joe and Barry try to gaslight her, Patty calls Barry with a fake emergency while on the train to see if and how quickly the Flash shows up. When he realizes he's been caught, he stops vibrating his face in front of her, proving to Patty she was right before they part ways.
- Disappointed by the Motive: Barry is less than impressed with Thawne's reason for hating him.
- Enemy Mine: Much to Barry's anger and disbelief, he has to help Thawne return to the latter's own time to save Cisco's life.
- Event Title: There's a "returns" in the title.
- Forgiveness: Joe and Iris come to terms with Francine on her death bed.
- Freudian Excuse: Averted. We finally learn why Eobard Thawne hated Barry so much, and it clearly upsets Barry that his mother, Eddie, and several others died for completely shallow reasons.Barry: That is why you killed my mother? That's why you ruined my life? Because you couldn't be me?
- Have We Met Yet?: From Thawne's point of view this is the first time he and Barry meet - in other words their timelines are in reverse.
- Green-Eyed Monster: The reason Thawne is the monster he is is as simple as it is petty: He wants to be better and faster than the Flash. This lines up with his origin story in the comics.
- Hidden Depths: See Shout-Out to Shakespeare.
- Hoist by His Own Petard: Lampshaded by Cisco, who notes that Eobard Thawne was (once again) imprisoned in the pipeline that he helped/will help to develop, and by powers that he gave/will give to Cisco.
- Internal Reveal: Patty works out that Barry is the Flash.
- Ironic Echo: Barry delivers to the Reverse Flash a line similar to the one he received from him in their first fight.Barry: Not fast enough, Thawne.
- Jerkass Ball: An intentional example; Barry is just plain cruel to Patty in this episode as a way to Break Her Heart to Save Her (see above).
- Joker Immunity: The Speed Force saved Thawne from being unborn, ensuring that he will encounter Barry more times in the future.
- Mad Scientist: Present in Eobard's first appearance, but very evident here. He's a scientist fascinated by Cisco's powers and other scientist curiosities around him. And he's also The Sociopath and has no problem using violence as a first option.
- Meaningful Echo: Thawne says "I win again Flash," something he said (technically later in his personal timeline) earlier in season one. Seemingly doubles as his Catchphrase.
- Mythology Gag:
- Jay Garrick's Earth-1 counterpart is named Hunter Zolomon. Hunter Zolomon is known in the comics as Zoom, the second Reverse-Flash and Wally West's nemesis.
- Eobard Thawne's motivation and Origin Story of idolizing The Flash and finding out he's his biggest enemy, which drives him to become evil is taken from the Wally West storyline "The Return of Barry Allen."
- Never Give the Captain a Straight Answer: Likely the most egregious example ever. When asked about his Earth-1 counterpart, Jay ominously tells Caitlin that she had to see for herself. When she arrives we find the alternate Jay sitting on a park bench, pointed out by ours, and he explains that "Hunter Zolomon's" mother died in childbirth and he was passed around between relatives, finally being adopted and having a different name. "I found my alternate; he's adopted so he's got a different name" is really not that hard a sentence! Not only does NOTHING about that require Caitlin to come all the way to the park, Earth-1 Jay/Hunter could've left the park by then to boot.
- No Ontological Inertia: Cisco's existence is implied to be heavily tied to Eobard Thawne's.
- O.O.C. Is Serious Business: Barry gives Thawne such a brutal beating that Joe has to remind Barry not to kill him.
- Origin Story: For Eobard. Lampshaded by Harry.
- Properly Paranoid: Jay is immediately suspicious of how the Turtle seems to have died the very night he was captured. Harry is only Digging Yourself Deeper by denying Jay's accusation, even though Jay didn't say anything.
- Psychic Nosebleed: Cisco's starting to experience nosebleeds ever since he Vibed with Harry's custom-made goggles.
- Psychopathic Manchild: The main reason Thawne hates Flash. Because he saw he would never be the Hero Flash was.
- Put on a Bus: Patty leaves for Midway City to become The Coroner, since Barry wants her out so Thawne or Zoom don't hurt her.
- Rapid-Fire Fisticuffs: Barry delivers this to the Reverse Flash before knocking him out and sending him to the Pipeline.
- Ret-Gone:
- Discussed. Everyone points out that Eobard Thawne no longer exists. But Harry explains that from Eobard's POV, that hasn't happened yet — time is protecting him while he plays out his history.
- This nearly happens to Cisco, but luckily sending Thawne back to his proper time fixes things.
- The Reveal: Barry finally finds out why Thawne hates him so much: Thawne was the Flash's biggest fan so he tried to become just like him, right down to copying the lab accident that gave him his powers. Much to his horror, he found out he was destined to be the Flash's greatest enemy, so he snapped and became the reverse of everything Barry was.
- Same Character, But Different: This is the Earth-1 Eobard Thawne, just from a future where he is still at the beginning of his career.
- Saved by Canon: Thawne is this, in a Timey-Wimey Ball sort of way. He can't be killed or permanently imprisoned before he discovers The Flash's identity, goes back in time to try to kill him as a child, and subsequently gets stuck (leading to the events of Season 1). Team Flash actually manages to capture him but are forced to let him go to avoid creating a Temporal Paradox. Barry isn't pleased.
- Screams Like a Little Girl: Cisco when he sees Harry wearing the Reverse Flash suit while in the Time Vault.
- Set Right What Once Went Wrong: Averted. Harry affirms that there is no way Barry can ever save Nora because it's now a fixed point in time - or rather nothing they do to Thawne in the present will save her because it's already happened in the past.
- Shout-Out:
- Harry says that Barry needs to get "better, stronger, faster."
- Nora Allen's death being a "fixed point in time."
- Shout-Out to Shakespeare: When Team Flash are examining the Turtle's corpse in the pipeline.Cisco: He better not be pulling a Juliet. Yeah, that's right. I see plays.
- So Last Season: Zig-Zagged. Barry is now faster and stronger than Eobard, but this Eobard is from a future where he is still at the beginning of his career as the Reverse-Flash. Thawne can't use his Speed Force powers as efficiently as he will (he can't toss effective punches and doesn't know any of the wrestling moves at this point in time), but it's shown that the significant vibrating hand move was one he learned early on in his career.
- Stable Time Loop:
- Eobard's first trip to Central City is how he finds out about STAR Labs, Dr. Wells, and (eventually) Barry's identity, setting up how he will kill Barry's mom in the future.
- Also, Eobard only became the the Flash's arch-nemesis and 'opposite' because he discovered while time-travelling that he was destined to do so. And thanks to Cisco, he may have found the idea for hiding his suit in the Reverse-Flash ring.
- Subverted in the end, as Barry and company trying to imprison him for good does have an effect on the timeline...it's just a very bad one, so they have to release him.
- Suspiciously Specific Denial: Harry goes out of his way to deny having anything to do with the Turtle's death...when he wasn't really accused of it in the first place.
- Temporal Paradox: Keeping Thawne in the Pipeline has major consequences.
- Tempting Fate: Harry just have to wear the Reverse-Flash suit while on the time vault, didn't he?
- This Cannot Be!: Team Flash's reaction upon discovering that Eobard is back despite being Ret Goned.
- This Is Unforgivable!: Eobard faces the wrath of the people who was/will be affected by his actions.
- Timey-Wimey Ball:
- The show's Time Travel logic is stretched further than ever before to explain how a "temporal echo" of Eobard Thawne can still exist after his family tree was cut short. Nora's death being a fixed point in time is also a brand new supposition that could have saved everyone a lot of trouble last season. It does however explain how Future!Barry was still able to exist despite his entire timeline being changed and why he warned his other self not to save Nora.
- Not to mention, this episode freely makes use of both the Alternate Timeline and Stable Time Loop theories. Despite being a relic from an erased timeline, Eobard's experiences in this episode are somehow part of a Stable Time Loop that sets into motion the events that lead to his timeline being erased in the first place.
- Villain Forgot to Level Grind: An unusual variant; Eobard was stronger, faster and more experienced than Barry in season 1...but the one who shows up in this episode is an earlier version of him, who is meeting the Flash in person for the first time and as such has no experience fighting him. Barry, meanwhile, fought his older self last season and now has more experience and training, not to mention he actually knows who he is facing this time. As a result, when the two have a proper fight in this episode, Barry is rather quick to make him bit the dust.
- Vitriolic Best Buds: Cisco and Harry are well on their way to becoming this. They're constantly bickering and sniping at each other, but Harry panics when Cisco starts being erased from history, showing that he has actually come to care about him. They go straight back to sassing each other once Cisco recovers, though.
- Wham Line: For comic readers, The Reveal of who Jay Garrick's Earth-1 counterpart is.Jay: "His name is Hunter Zolomon."
- Worf Had the Flu: Barry defeats Thawne relatively easy this time. However, this version of Thawne is from a time period where he hasn't been the Reverse Flash for very long.
- You Called Me "X"; It Must Be Serious: Harry actually calls Cisco by his first name as the latter is about to be erased from history.
- You Can't Fight Fate: Thawne's actions in Season 1 and before it is destined to happen.
- You Have Out Lived Your Usefulness: Thawne tries to pull this on Dr. McGee, but luckily Barry saves her in the nick of time.
- You Killed My Father: Eobard's past/future sins catches up to him as Barry still hasn't forgotten what he did/will do to his mother (and father). Harry also strongly implies that he is pissed at him for what he did/will do to his Earth-1 counterpart.
