‘The Flash’ Season 3 Episode 21 Recap and Review: Cause and Effect

The Flash season 3 episode 21
Grant Gustin as Barry Allen and Candice Patton as Iris West (Photo: Katie Yu © 2017 The CW Network)

“See, that’s the thing about time travel, Barry. The more you do it, the less the rules apply to you,” says Evil Barry (Grant Gustin) to the real Barry Allen as he reveals how he came to exist and why he wants to kill Iris (Candice Patton) in season three episode 21 of The CW’s The Flash. The episode begins right where episode 22 ended with Savitar revealing himself after Barry figured out he’d been fighting an evil version of himself all this time. Savitar reveals he’s a time remnant that Barry himself creates four years in the future to fight Savitar and that Savitar let him live so he could become Savitar in the future. (Confused yet?)

After Barry trapped Savitar in the Speed Force, everyone on Team Flash basically abandoned the time remnant making him feel lost, alone, and angry. That’s when the time remnant realized that “God feels no pain” and that all he needed to become a god was to kill Iris which would push Barry into the darkness and toward becoming Savitar. Barry threatens to kill himself but evil Barry reminds him that even though Eddie killed himself to get rid of Eobard Thawne, he’s still out there and that cause and effect is a tricky thing.

Evil Barry reminds Barry none of this would be happening if he hadn’t played god and created Flashpoint. Barry attacks evil Barry and is winning until evil Barry shows him that his Savitar suit can work without him in it and the suit attacks Barry. Evil Barry jumps into the suit and the two speedsters charge each other like bulls, slamming into each other and hitting each other with lightning. All the attack does is knock the wind out of them and set some bushes on fire before Savitar races off.


At S.T.A.R. Labs, Barry reveals the identity of Savitar to Team Flash, but Wally (Keiynan Lonsdale) and Joe (Jesse L. Martin) are having a hard time understanding it (they’re not alone!). Cisco (Carlos Valdes) explains it to them using the whiteboard, saying it’s basically an endless loop Barry has created that they need to break by stopping Savitar.

Wally asks how they can stop Savitar since he knows everything Barry knows. That gives Cisco the idea of altering Barry so he’ll temporarily stop making short-term memories allowing them to get one step ahead of Savitar. Joe and Iris are nervous about it, and Joe points out that Caitlin (Danielle Panabaker) is the brain expert and medical genius of the team. However, Barry says he trusts Cisco and they should try it. (Barry and Cisco made sad, regretful faces when Joe brought up Caitlin.)

With Julian’s (Tom Felton) help, they try their little experiment on his brain which unfortunately doesn’t just erase his short-term memory but a very large portion of it. Barry now has amnesia and comes to, asking, “Who are you people?” and wondering if he’s at the dentist. When they tell him he’s at S.T.A.R. Labs, he gets upset asking if they are experimenting on him. Julian admits they have…but with his consent. Cisco tries to get him back in the chair but Barry, now fearful, refuses until Iris tells him they are his friends and family. She tries to convince him by showing him photos of them together. (This scene is laugh out loud hilarious with Grant doing some great work here as innocent and goofy Barry who prefers to be called Bart.) Just as Team Flash’s gaining Bart’s trust, Joe gets a text that he and Barry are needed back at the CCPD. Iris and Joe take Barry to see what the emergency is while Cisco and Julian work on fixing Barry.

At the CCPD, Joe, Iris, and Barry learn from Cecile (Danielle Nicolet) that Barry needs to testify in court this afternoon against a pyromaniac named Heat Monger because Barry was the CSI who worked the case. Joe goes to court to try to call in a few favors to get it delayed while Iris talks to Barry who feels guilty about not remembering. He asks her if they have been planning their wedding and she sayst they’ve been busy. When he asks what they’ve been doing, she doesn’t tell him about Savitar or the fact that he’s The Flash because she’s enjoying seeing Barry without all the emotional scars and weight he carries from his past.

Meanwhile in Savitar’s lair, Killer Frost (Danielle Panabaker) is getting impatient. She reminds Savitar his ascension is soon and if he doesn’t come up with a plan to beat Team Flash, neither one of them will get what they want. However, as Killer Frost talks, Savitar remains kneeling and silent. “Hello, anyone in there?” asks Frost, tapping on his armor which causes him to jump up, grab her by the throat, slam her up against a wall, and ask who she is. Frost chokes out, “What’s wrong with you?” and Savitar replies, “Who am I?”

Barry ends up in court having to testify but Cisco and Julian have come up with a Hail Mary, making special tech glasses for him to wear. Julian can type the in-depth scientific answers Barry has to give during his testimony and he’ll see them on the inside of his glasses. This fails miserably as the sweat from Barry being nervous shorts out the glasses leaving him without answers in the middle of the testimony. Without Barry’s testimony, Heat Monger is released.

As Cisco and Julian are talking about what a failure that was, they enter S.T.A.R. Labs and are met by Killer Frost. Wally tries to attack her but realizes he doesn’t have his powers anymore. That’s because Savitar has also lost his memories and never went through with the plan to give Wally his powers – hence more cause and effect. Frost has figured out what they did to Barry and suggests if they want to fix him, they will do as she says.

At their apartment, Barry’s feeling terrible about letting Heat Monger off but Iris tells him it’s not his fault. He looks around, admiring their apartment, and asks who the couple in the photo are not recognizing his own parents. Iris tells him who they are but lies to him and says they died unexpectedly but peacefully. They kiss and that’s when Barry’s powers kick in. He moves super fast and falls over the sofa, asking, “What just happened?!”

In another part of the lab, H.R. (Tom Cavanagh) is trying to help and inspire Tracy (Anne Dudek) who’s struggling with a mental block in figuring out how to build the “Speed Force Bazooka” as H.R. has titled it. They also realize they both enjoy coffee to relax and that they’re falling for each other.

Joe, Barry, and Iris enter the main cortex of S.T.A.R. Labs and Barry’s excited about his powers and learning he’s The Flash. Unfortunately, Cisco, Wally, and Julian look serious and gloomy and Barry says that’s a buzzkill. Killer Frost says she has that effect on people and Joe pulls his pistol, but Cisco says she’s here to help. She tells them she can get Barry’s memories back and that will get everything back on track. Wally says that means Savitar will kill Iris and Frost replies, “Life is full of tough choices.”

In the medical bay, Frost tells Cisco he never should have tried doing this to Barry without Caitlin, and Cisco tells her to stop talking about herself in the third person. Cisco then tells Julian a story about when he, Caitlin, and Ronnie pulled an all-nighter working on the particle accelerator to try to reach Frost’s inner Caitlin. It works, and she quotes what her deceased husband yelled as he tried to get the machine to work. Cisco tells her that all the memories he cherishes the most have her in them, every single one. Frost becomes uncomfortable and moves away, telling him to focus and that she doesn’t want to be there any longer than she has to be.

Iris admits to Joe she doesn’t want Barry to remember his tragic past. She’s never seen him so light and happy, but Joe reminds her this isn’t the Barry she fell in love with or the Barry he raised. They need their Barry back with all his life experiences.

The Flash season 3 episode 21
Keiynan Lonsdale as Wally West, Danielle Panabaker as Killer Frost and Tom Felton as Julian Albert (Photo: Jeff Weddell © 2017 The CW Network)

Heat Monger attacks a high rise office building and Barry says he can’t let this happen. Barry wants to stop him but he doesn’t remember how to use his powers. As Barry arrives on the scene, he tells Team Flash he doesn’t know how to help the people inside. Frost tells them to use the device she and Cisco created. It will send a signal to the sensors in his suit to shock Barry‘s brain, zapping his memories back. They do it and Barry yells out in agony. He tells them through his com that he still can not remember. Frost tells them he needs to focus on a visceral memory. Iris finally does the right thing and tells him about the night his mother was murdered and how she comforted him. Barry’s mind clicks and he gets all his memories back. With that, he and the newly restored Kid Flash (Savitar’s memory also returns) put out the fire, saving the people inside the building and catching Heat Monger.

Back at S.T.A.R. Labs, Barry is quizzed by the gang and they’re satisfied he has his memory back. Joe says they can get back to stopping Savitar and Frost, who’s been watching and listening, says with a smirk on her face, “Good luck with that,” as she walks out.

As she’s waiting for the elevator, Cisco, Barry, and Julian catch up to her. She turns and asks if they want to fight and Cisco says no. Frost tells them there’s no way to avoid fighting her and Barry replies by saying, “Sure there is. Stay with us. We’re your friends. We’re your family.” Frost looks as though she’s listening to Barry for a moment but then turns to go to the elevator. Julian steps up and tells her to wait, that he’ll find a cure. She turns and tells him he tried and failed and Julian swears he’ll try again. He’ll never stop trying until he finds one. “Caitlin, I love you,” says Julian and Frost looks at him with surprise and just a touch of emotion before regaining her icy, cold composure. She replies, “I don’t love you, Julian, I never did. I never loved any of you.” Once the elevator doors close, Frost’s eyes turn from crystal blue to Caitlin’s lovely brown for a moment as Caitlin tries to take control. Frost fights Caitlin off and her eyes go back to crystal blue. (Come on, Caitlin, don’t stop fighting!)


Iris asks Barry if Frost is gone and he tells her she is and that he’s afraid they’ve lost her. Iris reassures him they’ll get her back, just like they got him back. She apologizes for not telling him earlier about his parents, but admits she loved seeing him so carefree and happy. Barry tells her he had that happiness in Flashpoint with his parents being alive, and he could have stayed there but it meant he would lose Joe, Cisco, Caitlin, Wally and even her. He explains he needs his pain and suffering and dark past to make him a better hero.

H.R. gathers Team Flash to show them what Tracy has created. They’re almost done with the Speed Force Bazooka but to power it they need 3.86 Techno Jewels…basically more power than the sun. The last scene shows the Dominator’s mind-control crystal being guarded by King Shark.

The Flash Season 3 Episode 21 Review:

Bright, lighthearted, and funny, season three episode 21 titled “Cause and Effect” is a much needed break from the intense and at times dark tone of the series. It injects back into the show what’s been missing since season one ended – the humor of The Flash – without becoming silly.

Grant Gustin proves just how versatile an actor he is by giving three strong performances in this episode. First as Barry Allen who’s determined to stop Savitar, save Iris, and bring back Caitlin from Killer Frost. Second his evil time remnant who’s filled with anger, hate, and sadness and wants to do to Barry what was done to him – break him. Third is innocent, carefree Barry or Bart (as he likes to call himself) who shows what Barry would be like without all the emotional scars and pain he carries. It’s this Barry that both Iris and the television audience are drawn to because of his likeable boyish nerdy charm and also the fact when he realizes he has powers he still wants to save lives. It serves to reinforce that at his core Barry Allen is a hero.

Another stand-out performance in this episode is delivered by Danielle Panabaker as Killer Frost. It’s amazing how Panabaker is able to subtly show the inner conflict going on in Frost as she struggles with Caitlin trying to come back. The scene where Cisco tells Julian the story of Caitlin’s husband Ronnie losing his temper as they worked on the particle accelerator and Frost’s eyes become softer as she finishes the line of the story is touching. Another great scene is where Julian tells Caitlin he loves her and for a few seconds Frost looks touched and surprised only to force herself to lie and tell he, Cisco, and Barry she doesn’t love any of them. It won’t happen but Panabaker deserves award recognition for her outstanding work this season.

With the Speed Force Bazooka in need of the alien crystal for power, it looks like Barry might have to actually steal it from its location with the help of an old nemesis turned ally, Captain Cold (Wentworth Miller).

GRADE: B

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