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"Well... things just got a lot more complicated, didn't they?"
Eobard Thawne to Barry Allen and Nora West-Allen

"What's Past is Prologue" is the eighth episode of the fifth season of The Flash, and the one-hundredth episode overall. It aired on December 4, 2018.



The 100th episodes of The Flash beginnings with Ralph and Sherloque marking out Orlin Dwyer. The two take a few pictures and come back to the group at STAR Labs to uncover what they found. The pair advise the rest regarding the group that he got his forces the evening of the Enlightenment and is executing metahumans in light of the fact that he censures them for the explanation his niece is in a state of insensibility.

The gathering begins talking about ways on approach to stop Cicada and Nora makes reference to they have to make a force housing gadget. They in the long run conclude that they have to go back in time so as to play out a "Period Hack," in which they'd plant a thing in the past that they'll require later on. They concur that they should plant the force housing gadget in the clinic before with the goal that they can enter the medical clinic later on undetected by Cicada.

Barry and Nora venture out through the Speed Force to return so as to when Barry went head to head versus Savitar with the goal that they can reclaim pieces required from Savitar's wrecked suit. After they return, they're before long followed out of the stream by a Time Wraith. Barry consents to lead the Wraith on a pursuit while Nora recoups the shard.

The two at that point travel back in time again to 2016 to recover the Speed Force transmitter Zoom recently utilized with the goal that Cisco can utilize the tech to manufacture the gadget. The two are halted by Zoom and lead him on a pursuit through the Speed Force. Barry and Nora drop out of the Speed Force and Nora in the end persuades her dad to remain in the time they dropped out in and find support from Eobard Thawne.

In the wake of persuading, Thawne consents to assist them with fixing the Speed Force canister recently taken. They at that point return in time again to the night the particle accelerator was first turned on. They sneak around the cellar of STAR Labs when Barry illuminates his little girl regarding his past with Thawne. Nora didn't understand that Thawne was liable for the passing of Barry's mom. The atom smasher goes off and the two utilize the canister and fixed tech to make the housing gadget. Barry phases it inside a column at the medical clinic and the two race back to present day.

Feeling that Cicada's forces are removed, Barry and group go to the clinic to go up against him. They're ready to get Cicada's blade away from him and Cisco vibes it into space. The achievement is brief since Cicada reviews the knife back to Earth and the different sides battle. In a little while, Cicada get away.

The group comes back to STAR Labs and Nora understands her diary is absent. She in the long run discovers Sherloque perusing it and he finds a section in a language he doesn't perceive. Nora says she made the language and Sherloque gives the diary back.

Nora leaves and we see that Sherloque was running an interpretation on his PC and this specific diary section being referred to peruses "the course of events is moldable." Nora races back so as to watch her grandparents talk from far off. She's watching them when Barry sneaks up behind her. The two watch them for some time before they dash off in a race.

Nora goes to Gideon's room at STAR Labs and has her hand-off a message to an inconspicuous beneficiary. When Gideon inquires as to whether there's whatever else she needs, Nora dashes off into what's to come. In the year 2049, we see Nora is working with Eobard Thawne.



Guest starring[]





Production began September 26, 2018.[1]


  • This episode is tied with Elseworlds, Part 1 as the highest rated episode of Season 5 with a rating of 9.0 on IMDb.
  • The episode's title is a reference to a famous line from the William Shakespeare play The Tempest.
  • Each main antagonist of the series' first five seasons appears in this episode.
  • Grant Gustin compared this episode to the Back to the Future film series. In both cases, characters travel to the past, revisiting previous scenes and observing younger versions of themselves.[2]
  • At the beginning of the episode when Ralph Dibny and Sherloque Wells are sitting in a car snapping pictures of Orlin Dwyer, Ralph asks how many pictures Sherloque's taken. Sherloque says, "I've shot like a hundred." This may be a nod to the fact that this is the hundredth episode of the series.
  • The dates Cisco Ramon writes on the board are the dates previous episodes aired.
  • As Barry Allen and Nora West-Allen begin to time travel into the past, Ralph plays the Huey Lewis and the News song "Back in Time", most likely another reference to Back to the Future.
  • The times Barry and Nora traveled to are from the following episodes:
  • Eobard mistakenly refers to Nora as "Dawn", a reference to Dawn Allen, Barry and Iris' daughter in the comics in the original timeline. He also says, "at least you still have one." This may be a reference to Barry and Iris having two children in the comics, the Tornado Twins: Dawn and Don Allen. However, in the context of the show, Eobard is more likely referring to how he killed Nora's namesake and Barry's mother, Nora Allen.
  • When Thawne is trying to figure out who Nora is, he guesses the names of three heroes:
  • It is revealed that Eobard somehow knows of Savitar, as he has already seen the latter's face to make fun of it.
    • Eobard's "pizza face" comment is similar to Cisco's insults to Savitar from "Finish Line", in which Cisco suggested to Savitar that he could make something to "fix that thin-crust pizza you call a face" while also referring to him as "Two-Face".
  • Sherloque and Eobard compliment Nora as a "clever girl". These were the famous last words of Robert Muldoon from Jurassic Park.
  • A young Grodd is shown, when Barry and Nora travel back in time to S.T.A.R. Labs, to the night when the particle accelerator exploded in 2013. His cage was seen in "Pilot", "Plastique", and "Grodd Lives".
  • When Nora asked why they didn't just speed into the Time Vault, Barry says it's because Thawne has been planning this night for years and if they used their speed, he'd feel it. Nora asks, "Like a disturbance in the Speed Force?" This is just like Obi-Wan Kenobi in Star Wars, when he felt "a disturbance in the Force".
  • The way Eobard Thawne as Harrison Wells extends his flat out hand, to shake hands with Cisco, is similar to the erased timeline in "Out of Time", when Harrison reveals his true identity as Eobard to Cisco before killing him by phasing his hand through his chest. The music in the scene is also based on the original scene's musical track, "Dead to Me".
  • At one point, Gideon was about to say that Nora is the fifth recruit of a rebooted Legion before Barry interrupted her. Similarly, in the "The Trap", Gideon was about to say that Barry is the founder of an organization before he interrupted her.
  • Barry tells Nora why Thawne killed his mother in the context as he was told by the Reverse-Flash in "Fast Enough".
  • When Barry and Nora return to the present, Ralph asks, "Did you even go?" (since they returned to the moment they left). Caitlin Snow asked Barry the same question when he returned to the present after running back in time in "Flash Back".
  • While translating Nora's journal, Sherloque discovered the phrase, "The timeline is malleable." This line was previously said by Rip Hunter in the DC's Legends of Tomorrow episode "Star City 2046".
  • Barry and Nora visit the Allen house to see Henry and Nora Allen prior to the latter's murder. Nora asks if Barry ever thought about stopping it, where Barry admits, "Every day." This already happened in "The Race of His Life" and "Flashpoint", in which he created Flashpoint.
  • Rick Cosnett (Eddie Thawne) was originally going to appear in this episode.[3]
  • Despite being credited in this episode, LaMonica Garrett only appeared in the end of this episode, which also served as the opening scene from "Elseworlds, Part 1" shown as a teaser. The scene also features John Wesley Shipp as The Flash of Earth-90, thereby confirming The Flash 1990s television series existence within the Arrowverse after "Welcome to Earth-2" which featured the multiverse.


  • There are a few inconsistencies to the past seen when Barry and Nora travel back in time:*
    • When Iris shot Savitar in "Finish Line", he fell lying face-up. In this episode when Barry and Nora travel back to that night, Savitar was lying face-down after Iris shot him.
    • After Zoom kidnaps Caitlin, Cisco runs and calls out to her. In this episode, he is shown looking from behind a closed door, which wasn't closed during the events of "Versus Zoom".
    • When Barry and Nora travel back to the events of "Versus Zoom", Iris checks on Barry after Zoom steals his speed. However, in the original episode, Iris checked on him before that happened.
    • The hairstyle Eobard Thawne was sporting is completely different to the one he was seen with in "Flash Back".
      • Furthermore, his hairstyle matched with his original likeness, unlike his Wells' disguise.
    • On the night of the particle accelerator explosion, Cisco's hair is far longer than it was in the original time frame.
  • Zoom doesn't appear to recognize that Barry traveled back in time; when alerted to Barry and Nora's presence via their usage of the Speed Force, he didn't ask how Barry had his speed back, which he'd taken from the younger Barry moments earlier. After Barry lost his speed in "Versus Zoom", he didn't regain his powers until three episodes later in "The Runaway Dinosaur".
    • However, it's possible that Zoom had simply deduced that Barry and Nora had come from the future.
  • The timeline is now even more messed up due to the Time Wraith that showed up when Nora and Barry went back to the night of May 23, 2017 (Savitar's defeat) to get a shard of Savitar's armor. The Time Wraith followed them to the day Zoom stole Barry's speed and grabbed Zoom when he went after Barry and Nora. Zoom was taken by the Time Wraith at the wrong time; he was originally captured in "The Race of His Life".
    • However, the Time Wraith could have simply removed Zoom from the Speed Force and returned him to his proper place in time with his memory of the encounter with Nora and future Barry wiped, thus preventing any significant changes to the timeline.
  • The episode's official synopsis states that Sherloque takes his concerns about Nora to Iris. In the episode though, he discusses his findings with Cisco, not Iris.
  • After fixing the Speed Force transmitter for Barry and Nora, Eobard sees that Barry's past self from "Flash Back" has woken up in the Time Vault, but a moment after this Barry is shown to still be unconscious.
  • The amount of time it takes Barry and Nora to sneak into the cortex on the night of the particle accelerator explosion appears to be less than the amount of time that passed between Eobard's press conference speech and the accelerator's launch based on what was shown in "Things You Can't Outrun".
    • It's possible that more time passed between the press conference and Barry and Nora's entry into the hall outside the cortex, but it was simply not shown in the episode.
  • Eobard, as Harrison Wells, is powerless as stated by Gideon, but is seen to possess some leftover speed as evidenced when he flicked his hands, red lightning was emitted from his fingers.


  1. It's possible that all changes to the past shown when Barry and Nora went back in time are the result of ripples caused by their time traveling or, in the case of anything prior to 2016, Flashpoint.