As the idiom goes, you can’t know where you’re going unless you know where you’ve been. Unfortunately for all of us not named Barry Allen, we don’t have the opportunity to travel back in time to fully understand our past.
And that’s precisely what Barry has to do in “Flash Back” as he figures out just how to make himself faster. He realizes the key to matching the speeds of the Reverse-Flash and Zoom is to turn to one of them, and so he decides to face the first man who betrayed him, Eobard Thawne.
(Wally happens to be the one who gives Barry the idea of turning to an old master in the field while at dinner with the West family. That dinner also plants the seeds of one of Barry’s other goals as he heads back in time after he hears Iris lamenting she still feels guilty for dating after Eddie.)
Cisco, Caitlin, and Barry (Harry finds the whole ordeal asinine) concoct a plan for Barry to head back in time to the era of the Pied Piper. They plan a six-hour stay, during which time Barry can assume the identity of his past self, work with Wells/Eobard Thawne on a speed force formula, and return to the present, all without greatly disturbing the time stream.
Smooth plan, right? Well, naturally things go wrong almost from the start when the mysterious offspring of a Dementor and Ringwraith appears in the time stream alongside Barry before he pops out into the season 1 timeline too early.
He catches his earlier self confronting Hartley, and after the Pied Piper knocks pre-Barry out, the visiting Barry swoops in, grabs his former self, and attempts to knock him out with a Caitlin-concocted serum. Unfortunately, he’s caught off guard (by himself), and the two fight for the serum until the season 2 Barry finally gains the upper hand, sedates season 1 Barry, and switches their emblems to avoid suspicion.
Barry tries to play it cool once arriving at S.T.A.R. Labs with Hartley in tow. He generally avoids influencing the past with his knowledge, though he does help Cisco prevent what should be Hartley’s breakout. (Perhaps it’s just been a while since I’ve watched the early episodes, or maybe it’s just the show’s desire to show the difference in the team from then to its current state, but everyone seems if not colder, then less cohesive. Caitlin is even quieter while Cisco seems almost overwhelmed at times, and knowing Wells/Thawne looms over it all doesn’t help take the edge off.) He attempts to broach the subject of the speed formula with Wells, but the so-called time wraith pulls him away from his primary objective.
The wraith attacks the police station, snooping around in Barry’s lab and at his conspiracy theory corkboard. He arrives on the scene to find the wraith leaving, but he also, for the first time, sees Eddie Thawne alive once again.
Eddie’s whole not-dead thing has Barry shaken up (as much as season 1 Joe, while working with season 2 Barry, thinks it has to do with his declaration of love to Iris). Only further knocking him off his game, Barry heads back to S.T.A.R. Labs and mentions he already saw the wraith earlier that day.
He tries to provide a reasonable explanation for where he saw it, but Wells has caught on to Barry’s game. He knocks the future speedster up and locks him in his secret room demanding answers. Seeing Tom Cavanagh back in action as Wells-as-Thawne is a delight, particularly in his confrontation here with Barry. He’s in full-on angry whisper mode as he demands Barry to reveal who he is.
And so Barry does…to an extent. He tells Thawne he’s from the future and has come back looking for the answers to the speed force equation. Thawne is worried, though. If Barry can come back, it must mean Thawne failed, so Barry spins a yarn telling Thawne he made it home but in doing so formed a singularity. Barry has returned to learn how to be faster and stop the singularity, and while Thawne is initially reticent to help his enemy, Barry mentioning he’s left a letter explaining how to stop Thawne for his former self forces his foe’s hand.
NEXT: Time’s running out as the wraith’s wrath grows