"Cause and XS" is the fourteenth episode of the fifth season of The Flash, and the one-hundred-sixth episode overall. It aired on February 12, 2019.


After Iris lands in serious danger, Nora races to save her mother. Barry puts the finishing touches on the meta-human cure, leaving Cisco with a rare night off so he decides to take Kamilla Hwang on a date.[1]


  • The episode's title is a play on the phrase "cause and effect". Coincidentally, that very phrase was the name of an episode in season 3.
  • This is the first episode since "Seeing Red" and the third since "The Icicle Cometh"​ to feature Cecille, despite Danielle Nicolet being credited as a series regular. Furthermore, in this episode, Cecille appears but doesn't say anything.
  • Nora resets the timeline 52 times (53 if the time where no one gets killed is counted), a reference to the famous DC number 52.
  • Cisco states that giving the cure to Cicada in a month would be very fast for them to stop a villain. This is a fourth-wall reference to the fact that it takes a full season for Team Flash to defeat each main antagonist.
  • Barry teaches Nora about time travel, using the example of a coffee cup being like the space-time continuum, breaking whenever you travel through time, closely quoting what Jay Garrick had told him about the consequences of time travel in "Paradox"​. 
  • The animation when Nora runs back in time is somewhat similar to the animation of Earth-90's Barry Allen being thrown through time in The Flash​​.
  • The events of this episode are very similar to the events of the DC's Legends of Tomorrow​​ episode "Here I Go Again"​, in which Zari Tomaz dreams that she's stuck in a time loop, reliving the same hour over and over again with the Waverider exploding at the end of each loop. Here, Nora ends up being able to run only one hour into the past to keep anybody on Team Flash from getting killed by Cicada.
    • In addition, in "Here I Go Again", before Zari realizes she's stuck in a time loop, she feels as if she's experiencing déjà vu. In this episode, due to the fact that his powers allow him to remember things that have happened to him in erased timelines, Cisco gets the feeling that he's having déjà vu.
  • The first time that Cisco goes on his date with Kamilla (before Nora resets the timeline for the first time), he says that the company he works for is called Ramon Industries, a possible reference to the company he owned in the Flashpoint timeline.
  • It's revealed that Kid Flash and Cicada both have drinks served at CC Jitters named after them.
    • In all of the instances where Cisco goes on his date with Kamilla, a man named Ian orders a Cicada, but in the last iteration of the timeline (where none of Team Flash gets killed), he orders a Kid Flash instead.


  1. "The Flash - Episode 5.14 - Cause and XS - Press Release" - SpoilerTV
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