Warning: This article contains spoilers for The Flash season 5, episode 13.
The latest episode of The Flash season 5, "Cause and XS," saw Nora West-Allen break all the rules of time travel in order to prevent one of Team Flash being killed by Cicada. With Barry Allen stuck in the Speed Force for an hour, Team Flash was more vulnerable than ever before; and it fell to Nora to protect them, reversing time until she somehow managed to save everyone from the threat of Cicada.
Even though Nora ultimately saved the day, Cicada seems to be getting disturbingly close to Team Flash. He's successfully identified Iris as the journalist who broke into his house in the previous episode, and he knows she works with the Flash and the other heroes. He may not be a genius on the level of the Mad Thinker, but Cicada is clearly no fool, and it's just a matter of time before he puts the pieces together. If Team Flash don't stop him soon, then he'll stop them.
Given history was rewritten 52 times this episode, at first glance it's tempting to dismiss this as just a "filler." But in actual fact, "Cause and XS" is a vitally important chapter in The Flash season 5 - all because of one key detail. Let's explore the key questions raised by The Flash season 5, episode 14.
8. Why Is Thawne Working With XS?
The partnership between Thawne and Nora in The Flash season 5 has always seemed to be an unlikely one, and it's safe to assume that the villain is manipulating Nora to his own ends. "Cause and XS" offered an important hint as to what Thawne's goals really are; it seems he's persuaded Nora that the way to save her father from his disappearance is by destroying Cicada's dagger. It's reasonable to assume that, in reality, destroying the dagger will change own Thawne's past - in his favor. That dagger is actually a powerful potential weapon. Any meta in close proximity to it loses their powers - including speedsters like the Flash and Thawne. It's possible that in Nora's timeline, that dagger leads to one of Thawne's greatest defeats, and he's attempting to rewrite it.
7. If Team Flash Win, Will This Move Up The Crisis?
If Nora succeeds in destroying the dagger, will she be responsible for causing her father to disappear sooner rather than later? The Flash has always been headed towards an adaptation of the classic "Crisis on Infinite Earths," a story in which Barry Allen sacrificed himself to save his world from an interdimensional threat. That was teased all the way back in the pilot episode, when the Reverse-Flash contemplated a newspaper from 2024 with the headline "Flash Vanishes in Crisis." The show has given a lot of subtle hints and clues over the years, confirming that Thawne himself is a key part of the Crisis.
There's one wrinkle: the Arrowverse is heading for the Crisis sooner rather than later, with "Crisis on Infinite Earths" now confirmed as the 2019 Arrowverse crossover event. Viewers have theorized that Nora's presence in the present will somehow accelerate the Crisis, meaning it happens in 2019 rather than in 2024. This may explain how; perhaps Nora will succeed in her goal, destroying the dagger and changing time, but somehow leading to her father facing this interdimensional threat five years early.
6. Will There Be Any Consequences From Nora's Time Travel?
As Barry Allen explained to his daughter at the end of "Cause and XS," time travel has unpredictable consequences. Whenever a speedster attempts to rewrite history, it breaks the fabric of the time-space continuum, and nothing is ever quite the same again; at worst, the speedster creates an entire alternate universe, as seen in The Flash season 3's "Flashpoint" arc. So will there be any unexpected consequences from The Flash season 5, episode 14? Nora seems to have gotten away with all her time travel escapades so far, but that doesn't rule out repercussions from her 52 attempts to change the past.
5. Why Did All The Timelines Take Exactly An Hour?
While "Cause and XS" serves an important purpose in the overarching arc of The Flash season 5, giving Nora another reason to distrust Thawne, the plot is frankly rather contrived. It's altogether too convenient that every one of the timelines plays out in an hour, meaning Nora's father doesn't return from the Speed Force in time to affect how things work out. That's particularly the case in the timelines where Cicada raids Iris' office, sees her family photos, and tracks down and murders Cecille. This feat is all the more impressive when you remember that Cicada didn't know the Flash was unavailable, and had no idea he was working to a clock.