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Quote1 It's why you didn't want me to come with you, isn't it? It's not because it was dangerous, or because of the timeline, but because you didn't want me to know these awful things about you so it's not what I would remember most when I went back. Quote2
Nora West-Allen

What's Past Is Prologue is an episode of season 5 of The Flash. It premiered on December 4, 2018.

Synopsis for "What's Past is Prologue"

Appearing in "What's Past is Prologue"

Featured Characters:

Supporting Characters:


Other Characters:




  • Mardons' Airplane (Destroyed) (Cameo)
  • S.T.A.R. Labs Mobile Research Unit




  • This is the 100th episode of The Flash.
  • Team Flash's story continues in the Elseworlds crossover which begins in the next The Flash episode, "Elseworlds, Part 1".
  • Barry and Nora travels back in time to many past episodes:
    • The night of the Particle Accelerator Explosion from "Pilot";
    • The day Barry returned to the events of "The Sound and the Fury" to ask for Thawne's help in enhancing his speed from "Flash Back";
    • The day that Zoom stole Barry's speed in "Versus Zoom";
    • The last standing between Team Flash and Savitar in "Finish Line";
  • Eobard Thawne mentions that Barry's daughter was called Dawn in the original timeline.
  • Thawne knowing about Savitar implies that his own timeline was also altered as a consequence of the Flashpoint because he didn't exist in the original continuity of Earth-1 as well as Thawne's original future.
  • Zoom is seen being dragged into the Speed Force many months before his capture in "The Race of His Life". However, this doesn't seem to affect the timeline in a major way for unknown reasons.
  • The Thawne from 2049 is the same iteration that fought Barry during the Earth-X invasion.
    • His hair turning blonde once again implies that the effect of his appearance-stealing device eventually wears off.
  • The origin timelines of Danica Williams and Libby Lawrence will never be revealed in any Arrowverse episode/story.
  • This episode also reveals that a version of the Legion of Super-Heroes exist in Nora's Future.


See Also

Recommended Media

  • None.

Links and References

  • None.


  1. 1.0 1.1 The Flash: The Legends of Forever
  2. The Flash: Johnny Quick
  3. The Flash: The Tornado Twins