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"Part of him is. He said it was like looking in a mirror, and he was right. But not just the way that he looked. It was... it was his eyes. The pain that was inside them. I've seen that in myself. When I think about how my parents died so violently. Sometimes I want to repay that violence with more violence. I wanna make someone else hurt as much as I do."
"But you don't ever do that. You're not him, you're a good person."
"I know, but it's in there, you know. That's in me. That power, that pain. That's where Savitar comes from. From loss. From losing you.
Barry Allen and Iris West on Savitar

"Cause and Effect" is the twenty-first episode of the third season of The Flash, and the sixty-seventh episode overall. It aired on May 9, 2017.



Barry comes face-to-face with Savitar, whom he had deduced to an evil future time-remnant of himself. Savitar reminds Barry of the first remnant he created to defeat Zoom and save the multiverse. It was because of his duplicate's sacrifice that his happy life would've continued until Barry created Flashpoint and changed everything. Though 2024 Barry had created multiple time remnants that died fighting Savitar, he neglected to mention to present Barry that the lone survivor was shunned by the future Team Flash because he was an aberration. Eventually, Savitar came to the conclusion that if he became a god, all the emotional pain he felt would be buried. Now all he needs to do is kill Iris to drive Barry so far into the dark that Savitar can be born, but declines to mention the second thing, saying it'd be ironic to mention it.

Barry threatens to commit suicide to erase Savitar from existence but his opponent argues that time travel is not so simple, reminding that the same happened to Eddie Thawne yet Eobard still lives; as far as Savitar is concerned, the more one time travels, the less the rules apply. Though Barry points out that the two of having this conversation means they're changing the future. However, Savitar is convinced that his ascension is inevitable and promises that once he has control over all of time, Barry would be the one who is abandoned and forgotten.

As Savitar turns towards his arm, Barry delivers a quick uppercut and gets him in a headlock, threatening to kill him on the spot. Savitar boasts that his suit is cooler than his as the armor suddenly comes to life and throws Barry away. Savitar then quickly re-enters his suit and starts running in a circle. Barry does likewise and they both throw lightning at each other. The two attacks collide, causing an explosion that throws both combatants back. By the time Barry recovers, Savitar had already fled.

Barry returns to STAR Labs and tells the remainder of the team what he learned. Cisco deduces that the message the Legends found on the Waverider warning against trusting Barry Allen was actually a warning against Savitar. He then draws on the board to explain Savitar is the creation of a closed loop.

Wally then questions why Savitar, a duplicate of Barry and possessing his feelings and memories, would want to hurt Team Flash. Barry sidesteps the question to ask HR to get Tracy to double her efforts on the Speed Force weapon.

Iris approaches Barry in the Speed Lab and the two have a snappy conversation about what communicating with Savitar resembled. Barry advises Iris that Savitar was made from the torment that Barry has endured his life — the loss of his mom, the loss of his dad, and the loss of Iris. Cisco at that point surges in and discloses to them he has a thought.

Cisco shows Barry a machine he's assembled, one that will remove Barry's ability to create new memories, given that Savitar can remember everything he does. Among Cisco and Julian, the two clarify that in principle, deleting Barry's memories should render Savitar incapable of thwarting them.

Cisco powers up the machine and Barry experiences a concise arrangement of his past memories. After Julian asks how he's doing, Barry out of nowhere acknowledges he doesn't recall that anybody in the room, soliciting "Who are every one of you?"

Barry proceeds on a short befuddled digression, Julian and Cisco conclude that Barry is experiencing a type of amnesia.

Cecile calls Joe and notices that she needs Barry at the police office to help manage a crisis; Joe and Iris choose they'll take him while Julian and Cisco remain behind to take a shot at an answer.

HR strolls into the room where Tracy Brand is as yet taking a shot at the Speedforce trap and after a short second where the two almost share a kiss, they step back and proceed with work.

At the police division, Cecile examines a case wherein Barry needs to affirm for the arraignment and Joe clarifies the motivation behind why Barry can't affirm. With Iris and Barry off to get food, we see Killer Frost approach Savitar.

Savitar isn't reacting and when thumping on his suit, Savitar snatches her by her throat and pins her against the divider. It's uncovered that Savitar doesn't have the foggiest idea who he is, demonstrating that Cisco's amnesia machine worked.

Iris and Barry are having an espresso at Jitters when Iris imparts to Barry a portion of the pastimes he has, trying to get his memories back. Iris clarifies her energy since it appears Barry is upbeat.

Barry gets called to the town hall when Cisco and Julian burst in and give Barry a pair of glasses. Barry is called to the stand and it's shown that the glasses display text that Julian types from a computer.

With Cecile addressing him, Barry responds to her inquiries, using information that Julian types. The glasses in the long run impede with Barry incapable to respond to the inquiries, the judge excuses the charges against the respondent.

Back upon their landing in STAR Labs, Julian, Cisco, and Wally are met by Killer Frost, who appears to have removed Wally's speed. She reveals to them that she'll help get his speed back on the off chance that they help her with something.

Iris and Barry are back at their place and Iris clarifies a few of the photos he's in. The two offer a kiss, which activates Barry's powers, leading him to speed around their lounge before stumbling over the love seat. He asks Iris, "What just happened to me?"

Iris and Barry head back to STAR Labs where they join the others and Killer Frost. Killer Frost clarifies that Wally lost his powers because Barry lost his memories, causing a similar issue with Savitar.

Cisco, Julian, and Killer Frost go to work in the lab, when Cisco starts revealing to Julian an anecdote about how they worked with Ronnie on the atom smasher. A troubled Killer Frost turns her back to the next two, at that point proceeds to complete Cisco's sentence.

Joe and Iris are trying Barry's forces when Iris makes reference to that she's never observed Barry this happy. She takes note of that despite the fact that this is an alternate variant of him, it's still Barry. Joe sets up a brief answer, contending that Barry has recently had 28 years worth of memories and the memory-less Speedster isn't the individual they've come to know and love.

The man who got off free in light of Barry being not able to affirm — Heatmonger — starts to light a place of business ablaze. Barry choose he needs to go out and save the individuals stuck in the building. On the scene, Cisco stuns Barry's cerebrum trying to kick off his mind trying to give him his memories back.

Cisco understands that the "gas is in the tank," and they simply need to turn the start. Iris at that point jumps in the group correspondences framework and starts experiencing their past. Barry sees another memory montage, his memories are back.

It slices to a fast scene with Savitar, his memories are back now as well.

Presently with his powers back, Wally joins Barry and the two put out the workplace fire and put Heatmonger in handcuffs.

Back at STAR Labs, the individuals from Team Flash start testing Barry on little goodies just he'd know. He breezes through the assessment.

Killer Frost starts leaving when Barry, Cisco, and Julian stop her. Julian notices that he can fix her, conceding he adores her. Killer Frost chomps back saying that she doesn't cherish him, nor any of different individuals from the group. She leaves in the elevator and for a split second, we see her eyes switch back to Caitlin's, only for a second.

Iris notices to Barry about how she enjoyed him being glad for once and Barry makes reference to that the torment and haziness is just what his identity is. The two start kissing when HR strolls in, saying they need to come see something.

It's uncovered that Brand that has finished her Speedforce trap, however it's uncovered they'll require more energy than what's available in the Sun. The scene closes with King Shark having been revealed as the attendant of the energy source they need.



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  • Cisco mentions the Star Trek: The Original Series episode "The Enemy Within" in which Captain Kirk is split into good and bad personalities.
    • H.R. mentions having Star Trek: Voyager on his Earth, to which Cisco claims to hate spin-offs. This is likely a tongue-in-cheek joke, considering the fact that The Flash is a spin-off of Arrow.
  • Cisco refers to Barry as "Steel Magnolias", referencing the 1989 film, Steel Magnolias.
  • After losing his memories, Barry asks to be called "Bart", a reference to Bart Allen, who is Barry and Iris' grandson in the comics.
  • Barry is revealed to have been a huge fan of anime in high school, with Iris mentioning that Dragon Ball Z was one of his favorites.
    • Coincidentally, this episode aired on the Japanese-recognized holiday "Goku Day".
  • Rather than "the Flash", Barry suggests that they call him "the Streak", a name which was first used to identify him in the first season of the show.
  • Mick Rory is mentioned at the CCPD as being "off the grid", indicating that the police do not know of his whereabouts. This alludes to Mick currently time-traveling with the Legends.
  • Even though Hartley Rathaway was seen to have made amends with Team Flash following the events of "Flash Back", Cisco still refers to him as a "dick" in this episode.
  • Barry's birthday is revealed to be on March 14, 1989 according to his driver's license.


  • According to Barry's driver's license, it says that he renewed it on March 10, 2014. However, Barry was in a coma from the time of December 11, 2013 to September 2014, so he couldn't have renewed it during this time, assuming that it has to be renewed in person (unless a military member or dependent) like in real-life Missouri that Central City is placed in.
  • Tracy states they require 3.86 terajoules (3,860,000,000,000) of energy to power the Speed Force bazooka, which Cisco claims is more than the energy of the sun. This is vastly inaccurate, as the sun releases 384.6 yottajoules (384,600,000,000,000,000,000,000,000) of energy every second.
    • 3.86 terajoules is also less than the approximate output of a nuclear power plant running at full capacity for two hours.
  • As Savitar's armor begins to attack Barry, Barry's mask is removed. However, shortly prior to the armor stepping on Barry, his mask is seen back on his face.
  • Closeups of Killer Frost's forehead show an obvious line of about 5 mm below her hairline where there is no Killer Frost makeup, as it's not properly blended.
  • Iris' flashback to the West house on the night Barry's mother died is slightly different from the version shown in "Fast Enough", "Flashpoint" and Versus Zoom, which in turn originated from a deleted scene in "Pilot". In the original scene, Iris comes down the stairs while Joe and Barry are at the foot of the stairs, and Barry is wearing a backpack; in this episode's scene, Iris is sitting on the stairs when Joe and Barry enter the house, and Barry is not wearing a backpack.