The Flash season 3, episode 21 recap: “Cause and Effect”


After discovering Savitar’s true identity, the Flash erases his own memories in order to stop the villain from being created.

“Cause And Effect” picks up where last week’s episode, “I Know Who You Are” left off, with the reveal that Savitar is really Barry Allen. Or to be more specific, a time remnant of the Flash. We’re given an example of the Flash creating a time remnant when he battled Zoom in Season 2. Once Flash went back in time and made Flashpoint, it changed everything.

We find out the future version of Flash sent time remnants against Savitar. The God of Speed allowed one of them to survive, which eventually goes on to become him. Hopefully, that wasn’t too confusing. Anyway, this remnant was shunned by #TeamFlash and is dubbed an aberration.

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Savitar tells Flash that a god feels no pain, and he only needs two more things to turn himself into one. The first being Iris West’s death in order to drive Barry to become Savitar. As for the second thing, Savitar is keeping that to himself for now.

The Flash has an idea to kill himself to prevent Savitar from being born. The villain has a comeback for this, however; the more you time travel, the more the rules don’t apply to you. An example is Eddie Thawne’s suicide not stopping Eobard Thawne from becoming the Reverse-Flash.

At this point, Barry’s heard enough out of Savitar and levels a speed force-induced uppercut to him. It becomes a two-on-one fight once Savitar’s armored suit joins the fray and he escapes. Back at S.T.A.R. Labs, Barry tells #TeamFlash what he’s learned. Cisco Ramon chimes in with the revelation that when the Legends of Tomorrow found a message in the Waverider from Future Barry saying not to trust himself, he was referring to Savitar.

Cisco draws a diagram illustrating how Savitar was created: Future Barry created a time remnant, which Savitar allowed to live so it could, in turn, travel to the past to become him while he’s trapped in the Speed Force. Joe West poses an excellent question, “Which came first, the time remnant or Savitar?” Cisco calls it a closed loop with no beginning or end.

The team has an idea on how to stop Savitar, but it revolves around the idea of erasing Barry’s short-term memories so Savitar won’t have a clue what’s coming. Unfortunately, all of Barry’s memories are erased instead. After the process, he doesn’t recognize any of his family or friends. They have to show him his driver’s license to prove he’s actually Barry Allen, or as his license reads, Bartholomew Allen. There’s even a quick joke about Wally West and Barry being brothers, which causes Barry to glance at the difference in their skin tone.

We get to check in on HR Wells and Tracy Brand as she works to develop the method to trap Savitar in the Speed Force. There’s a little bit of flirtation among the two of them. Meanwhile, Barry’s memory loss comes at a bad time as he’s called into court to testify against a criminal he helped put away. Just as his memory has disappeared, so has Savitar’s. Cisco comes up with some telecommuting glasses to give Barry during his testimony, with the idea of feeding him the answers through the glass lenses. This works for a few moments until Barry’s sweat short circuits them.

Killer Frost appears at S.T.A.R. Labs to find out what’s happened to Savitar. We discover that since Savitar doesn’t remember who he is, he won’t go on to eventually give Wally his powers, so no more Kid Flash. Killer Frost calls this “cause and effect,” which is the title of the episode. Meanwhile, Iris takes Barry back to their apartment. Even without his memory, he still wants to do good in the world. The couple shares a smooch, which is enough to trigger Barry’s powers.

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Back at S.T.A.R. Labs, Killer Frost works with Cisco and Julian Albert for a method to return Barry’s memories to him. Cisco tries telling a touching story about the old Caitlin to get to Killer Frost, which appears to work, if only for a few moments.

While this is going on, Barry is geeking out over his “newfound” powers. Iris confesses to Joe that part of her doesn’t want Barry to get his memory back. She’s enjoyed seeing the burden of being the Flash off his shoulders. Joe explains that even though Barry still has the qualities that make him who he is, it still isn’t the real Barry.

A fire breaks out in a high-rise building, thanks to the criminal that was freed in the courtroom earlier. The Flash heads out to help, but with his mind still fuzzy, isn’t able to help much. Iris gives Barry’s mind a kickstart by telling a story of the first time Barry was brought to the West home after his mother’s murder. This is enough to return Flash’s memories, along with Savitar’s.

The Flash and the renewed Kid Flash tag team the blaze, put the fire out, and apprehend the criminal. With everything back to the way it was, Killer Frost says bye-bye to her former friends. Julian begs her to stay, but Killer Frost says she never loved any of them.

Fear not, because HR and Tracy have created a Speed Force Bazooka to use against Savitar. The only downside is they need a special energy source to make it work. And as the episode closes, we see it’s guarded by the one and only King Shark.

Next: Catch up with a recap of 'I Know Who You Are'


The highlight of “Cause And Effect” was the opening confrontation with the Flash and Savitar. We received a ton of answers on how Savitar came to be, and how Flashpoint and time remnants played a factor. Time travel is enough to make your head hurt if you think about it too much, so its best to not ask too many questions.

Closing Thought

I believe we only have two more episodes before Season 3 concludes. Next episode brings the return of King Shark and Captain Cold. Not much time remains to give a fitting ending to this epic story. But, hopefully, the people behind-the-scenes won’t disappoint.