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"Cisco told me – or showed me – that you all haven't been a team in a long time. And I know that I'm the reason for that. Iris' death shouldn't have driven me away from you all. I mean, it should've driven me closer. This isn't what she would want. But I'm here now to tell you that no matter what happens in the past, I will not abandon you."
Barry Allen bringing Team Flash back together in the future

"The Once and Future Flash" is the nineteenth episode of the third season of The Flash, and the sixty-fifth episode overall. It aired on April 25, 2017.




Special appearance by

Guest starring




Promotional images



  • This episode aired on April 25 and takes place in 2024, the date on which the Flash is said to vanish in a Crisis, as published in a newspaper in the Time Vault.
    • However, the date Barry arrives in the future is February 3, 2024.
  • The title is a nod to an infamous inscription purported to be on the tomb of the legendary King Arthur in Le Morte d'Arthur by Sir Thomas Malory.
  • The title of this episode is a reference to the 1958 novel The Once and Future King by T.H. White, as well as the comic book The Flash #79, which was entitled "The Once and Future Flash".
  • While hiding in the Pipeline, H.R. slides under the closing door and retrieves his drumstick in the same manner that Indiana Jones does for his hat in Indiana Jones and the Temple of Doom.
  • While hiding from Killer Frost, H.R. and Cisco sing "Swing Low, Sweet Chariot", an African-American spiritual popularized by Eric Clapton.
  • In the future of this timeline, Barry and his friends' fates are revealed:
    • In the battle that Cisco vibed between him and Killer Frost earlier in the season,[1] she managed to freeze and shatter his hands, effectively depriving Cisco of his powers. Later, Cisco replaced his hands with mechanical prosthetics.
    • Killer Frost is arrested and incarcerated at Iron Heights Prison, with Julian taking care of her.
    • Wally went after Savitar by himself after Iris' death. Unfortunately, he lost and his spine was shattered, rendering him paraplegic. The aftermath of the fight sent him into a great shock for 7 years.
    • Joe doesn't get over Iris' death and regularly visits her grave.
    • H.R. is a celebrated author, having written a book titled The Streak vs Mr. Reflecto and reinvented CC Jitters into "HR Jitters".
    • Barry stopped being The Flash sometime after he defeated Savitar. He shut down S.T.A.R. Labs and began living there, abandoning his friends and leaving them without support.
  • This episode shares many similarities with the DC's Legends of Tomorrow episode "Star City 2046"​:
    • Both episodes take place in the future and feature an older broken hero (Barry in The Flash and Oliver Queen in DC's Legends of Tomorrow) living as a recluse in the remnants of their old hideout.
    • In the heroes' absence, a group of villains control their respective cities.
    • The heroes return to action when their former teammates inspire them and make them realize that their respective cities will always need them.
    • The episodes end with the heroes reforming their team and cleaning up their old hideout.
    • In both of these potential futures, someone has lost a limb and uses prosthetics to compensate; In 2046 Star City, Oliver is missing one of his arms (cut off by Grant Wilson) and uses a mechanical arm. In 2024 Central City, Cisco has lost both of his hands (shattered by Killer Frost) and uses a pair of mechanical hands.
  • This episode marks Tom Cavanagh's directorial debut.
  • This episode marks the first appearance of The Flash's new suit, which Barry wears the following season.
  • This was the first episode to feature Killer Frost but not Caitlin Snow in any capacity.
  • When he is face-to-face with Killer Frost, Julian has a lighting-bolt scar on his forehead, much like Harry Potter. Tom Felton portrayed Draco Malfoy in the Harry Potter film series.
  • Iris is mentioned to be born on June 24, 1989. This is exactly one year after Candice Patton's real-life date of birth.


  • Iris' birth date is shown on her tombstone to be June 24, 1989. However, Eddie Thawne stated that her birthday was "two months from now" in the portion of "Flash Back" that took place during the time period of "The Sound and the Fury", which aired in late January and presumably took place around the same time in-universe. This would place Iris' birthday sometime in March or April.
  • In 2024, H.R.'s face is pictured on his book and its promotional material, despite the general public knowing "Harrison Wells" to be the man who murdered Nora Allen.
  • When Barry was in 2024, he referred to himself as being from 2017. However, when he got home and H.R. asked him which year he went to, Barry said that he traveled eight years into the future instead of seven.