"Oh Flash. Come to save the day. Good! Now I can get rid of you too."
"Caitlin. You can fight this."
—Caitlin Snow and Barry Allen[src]
"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.


Barry travels to the future to find out Savitar's still unknown identity in the hopes of saving Iris. Upon his arrival in 2024, Barry encounters future versions of his Team Flash friends, who, following the death of Iris, have become very different people, profoundly impacted by their showdown with Savitar. It will be up to Barry to infuse a sense of hope back into the team, as he proves to be the hero his future friends have been waiting for. Meanwhile, back in 2017, the hunt for Killer Frost continues.[1]


  • 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.
  • 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, she managed to freeze and shatter Cisco's hands effectively, depriving him of his powers. Later, he replaced his hands with mechanical prosthetics.
    • Killer Frost is arrested and placed in a meta-human prison with Julian as her doctor.
    • Wally is revealed to have gone after Savitar by himself after Iris' death. Unfortunately, he lost and his spine was shattered. The aftermath of the fight sent him into a great shock for 7 years.
      • It's presumed Savitar revealed his identity as a time remnant of Barry to Wally, which the latter was unable to cope with.
    • Joe doesn't get over Iris' death and regularly visits her grave.
    • H.R. is a celebrated author with a book titled "The Streak vs Mr. Reflecto" and reinvents CC Jitters into HR Jitters.
    • Barry stops being The Flash sometime later after he defeated Savitar. He shut down S.T.A.R. Labs and abandoned his friends, 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 Allen 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 city.
    • 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 and uses a mechanical arm. In 2024 Central City, Cisco has lost both of his hands and uses a pair of mechanical prosthetics.
  • 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.


Promotional images



  1. Flash Spoilers: "The Once and Future Flash" Description - FlashTVNews