Tonight's episode picks up right where last week left off, current Barry and Savitar-Barry are seen having a discussion in the street.
Savitar reveals he's a temporal anomaly and a quick fight between the two breaks
Barry gets back to STAR Labs and tells the rest of the crew the identity of Savitar. The group starts brainstorming ways on how to stop Savitar.
Iris approaches Barry and the two have a quick discussion about what interacting with Savitar was like. Barry informs Iris that Savitar was created from the pain that Barry has suffered through his life — the loss of his mother, the loss of his father, and the loss of Iris. Cisco then rushes in and tells them he has an idea.
Cisco shows Barry a machine he's built, one that will take away Barry's memories. Between Cisco and Julian, the two explain that in theory, erasing Barry's memories should make Savitar cease to exist.
Cisco powers up the machine and Barry goes through a brief sequence of his previous memories. After Julian asks how he's doing, Barry suddenly realizes he doesn't remember anyone in the room, asking "Who are all of you?"
Barry continues on a
Cecile calls Joe and mentions that she needs Barry at the police department to help deal with an emergency; Joe and Iris decide they'll take him while Julian and Cisco stay behind to work on a solution.
HR walks into the room where Tracy Brand is still working on the Speedforce trap and after a brief moment where the two nearly share a kiss, they back away and continue work.
At the police department, Cecile discusses a case in which Barry needs to testify for the prosecution and Joe explains the reason why Barry can't testify. With Iris and Barry off to get food, we see Killer Frost approach Savitar.
Savitar isn't responding and when knocking on his suit, Savitar grabs her by her throat and pins her against the wall. It's revealed that Savitar doesn't know who he is, showing that Cisco's amnesia machine worked.
Iris and Barry are having a coffee at Jitters when Iris shares with Barry some of the hobbies he has, in an attempt to get his memories back. Iris explains her excitement now that it seems Barry is happy.
Barry gets called to the courthouse when Cisco and Julian barge in and give Barry a pair of glasses. Barry is called to the stand and it's shown that the glasses show the text that Julian types into a computer.
With Cecile questioning him, Barry answers her questions, via the text Julian types into his laptop. The glasses eventually short circuit and with Barry unable to answer the questions, the judge dismisses the charges against the defendant.
Back upon their arrival at STAR Labs, Julian, Cisco, and Wally are met by Killer Frost, who seems to have taken away Wally's powers. She tells them that she'll help get his power back if they help her with something.
Iris and Barry are back at their place and Iris explains several of the pictures he's in. The two share a kiss, which ignites Barry's powers once again and he zooms around their living room before tripping over the couch. 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 explains that the reason that Wally lost his powers is because Barry lost his memories, causing the same problem with Savitar, which rendered Wally's powers useless.
Cisco, Julian, and Killer Frost go to work in the lab, when Cisco begins telling Julian a story about how they worked with Ronnie on the particle accelerator. A bothered Killer Frost turns her back to the other two, then goes on to finish Cisco's sentence.
Joe and Iris are testing Barry's powers when Iris mentions that she's never seen Barry this happy. She notes that even though this is a different version of him, it's still Barry. Joe puts up a prompt rebuttal, arguing that Barry has previously had 28 years worth of memories and the memory-less Speedster isn't the person they've come to know and love.
The man who got off free because of Barry being unable to testify — Heatmonger — begins to light an office building on fire. Barry
Cisco realizes that the "gas is in the tank," and they just need to turn the ignition. Iris then hops on the team communications system and begins going through their past. Barry sees another memory montage, his memories are back.
It cuts to a quick scene with Savitar, his memories are back now too.
Now with his powers back, Wally joins Barry and the two put out the office fire and put Heatmonger in cuffs.
Back at STAR Labs, the members of Team Flash begin quizzing Barry on little tidbits only he'd know. He passes the test.
Killer Frost begins walking away when Barry, Cisco, and Julian stop her. Julian mentions that he can fix her, admitting he loves her. Killer Frost bites back saying that she doesn't love him, nor any of the other members of the team. She leaves in the elevator and for a brief moment, we see her eyes switch back to Caitlin's, just for a second.
Iris mentions to Barry about how she liked him being happy for once and Barry mentions that the pain and darkness is simply who he is. The two begin kissing when HR walks in, saying they have to come see something.
It's revealed that Brand that has completed her Speedforce trap, but it's revealed they'll need more power than what's available in the Sun. The episode ends with King Shark having been revealed as the keeper of the power source they need.
MORE FLASH NEWS: Killer Frost Turns Up At STAR Labs In 'Cause And Effect' Photos / What if The Flash's Savitar Reveal Is More Complicated Than it Seems? / Could HR Wells Hold the Key To Saving Iris on The Flash? / [SPOILER] Revealed as Savitar on The Flash
Based on the characters from DC, The Flash is from by Bonanza Productions Inc. in association with Berlanti Productions and Warner Bros. Television, with executive producers Greg Berlanti (Arrow, Supergirl), Andrew Kreisberg (Arrow, The Flash), Sarah Schechter (Arrow, DC’s Legends of Tomorrow) and Aaron and Todd Helbing.
"Cause and Effect" airs Tuesday, May 9 at 8 p.m. ET/PT.