Supergirl & The Flash: Worlds Finest Recap With Spoilers

03/28/2016 09:00 pm EDT

In the DEO, a doctor runs tests on a very upset Siobhan while Winn and Supergirl look on. Winn is worried about Siobhan, and who she might be. Supergirl is frustrated that the public still does not trust her after the red kryptonite incident.

The Doctor explains to Winn and Supergirl that Siobhan let out a soundwave so powerful that it cushioned her fall off the building (in the previous episode). But she is definitely human, no alien. Siobhan wants answers, and storms off angrily when the Doctor can't provide her any.

Winn catches up to Siobhan, who is furious that he never told her about knowing Supergirl or the DEO. He tries to offer comfort, claiming he will not abandon her. Suddenly, Siobhan sees images of a banshee, and she walks away from Winn. On her way out, she finds Lucy interrogating the imprisoned Livewire, and hears Livewire mention Supergirl and Cat Grant.

In Cat's office, Cat and Kara admire some very fancy cupcakes. Cat teases Kara about wanting one of the cupcakes and being afraid to ask for one, which swiftly morphs into a metaphor for Kara's lack of action in winning over James. Cat advises Kara to make James jealous. And in typical Cat form, refuses to share her cupcakes.

Siobhan walks down a busy sidewalk when she gets another vision of the banshee in her head. She suddenly changes directions.

At CatCo, Siobhan emerges from the elevator. Winn tries to stop her before Cat sees her in the building, but Siobhan shoves him aside and continues into the office. Cat orders Kara to call the authorities, but Kara tries to reason with Siobhan instead. Siobhan screams at Kara, her soundwave knocking Kara unconscious and sending her flying out the window. Suddenly, the Flash speeds up the side of the building, catches Kara, and makes it all the way to an open field before stopping.

Once they stop, Kara wakes up. She takes flight back to the city, but lands again when she sees The Flash running under her. They question each other and realize that neither of them have heard of the other, nor had Kara heard of any of the heroes of Central and Star City. Barry realizes he is in the wrong universe.

In the vacant officer at CatCo, Winn and James walk in on Kara and Barry getting to know each other. Winn immediately understands Barry's explanation of the multiverse and even helps describe it to a confused and sullen James. Barry also demonstrates his power by getting everyone ice-cream. When Kara and Barry head out for doughnuts, Winn calls James out for being jealous.

Cat calls Kara into her office before she can leave, and Barry, Winn, and James quickly follow. Cat has a picture of The Flash saving Kara, and she insists this new hero is competition for Supergirl. She also names him The Blur, much to Barry's chagrin. Cat sends all of the men from her office and tells Kara that James is clearly jealous of Barry, and she should keep it up.

Siobhan goes to a magic/crystal shop owned by her Aunt Sinead. She tells Sinead about the images of the banshee, and Sinead explains that the women of their family were cursed by a banshee long ago. It makes them all unpleasant people, and gives them the powerful scream once they are wronged. The catch is that they have to kill the person who wronged them, or else the power will take their souls. Siobhan doesn't know how she can kill Kara with both Cat and Supergirl protecting her. Then she remembers Livewire.

At the DEO, the sound of an enormous scream erupts, shattering the glass of Livewire's cell. She electrocutes her guards.

Kara goes into Cat's office to tell her that Livewire escaped. Kara wants Cat and Carter to go into hiding, but Cat refuses to run. She still trusts Supergirl to protect her. So Kara goes back to the vacant office to ask Barry for help.

The Flash speeds through the DEO while Supergirl and Winn watch. Lucy and several soldiers with guns show, but Supergirl vouches for The Flash. Barry pulls off his mask and explains he is a CSI, so Supergirl sets him up in Alex's lab.

Livewire finds her favorite beer in a cooler in an abandoned warehouse. Siobhan is there, and suggests they team up to get Supergirl, Cat, and Kara. After seeing a demonstration of Siobhan's powers, Livewire agrees. Provided Siobhan has a makeover.

James shows at the DEO, but starts to leave when he sees Supergirl with Winn and The Flash. Lucy catches him, and encourages James to go for it with Kara.

Barry figures out a way to track Livewire, and has found the warehouse. Barry and Winn want to build a trap, but Supergirl insists they can't wait, so she and The Flash head out.

Supergirl and The Flash arrive at the warehouse, where they are confronted by Livewire. The Flash tries to hit her with lightning, but she simply absorbs it and zaps him. Supergirl starts to join the fight, but a massive scream causes her eardrums to bleed. She recognizes Siobhan, who is sporting a very different look, including painting her face silver and to resemble the banshee from her visions. Going by the name Silver Banshee, she joins Livewire. Supergirl and The Flash hold them off, but The Flash realizes they won't win this time, and they leave.

On the balcony at CatCo, Kara apologizes to Barry for rushing him. She explains how she lost the city's trust and is now rushing and making mistakes trying to earn it back. Barry suggests she slow down and stop trying. He went through something similar, and the only thing that made it better was time. Kara can't fix this problem, but it will fix itself on its own.

James looks for Kara, but Winn explains she went to the DEO with Barry. Cat is also looking for Kara, when Livewire appears, and zaps James before he can use his watch to call Supergirl. Silver Banshee joins her, and Winn steps in front of her, begging Siobhan to be a better person than this. She won't look at him at first, but after letting him beg and plead awhile, she throws him back with a scream.

Barry shows Kara some earplugs he made them to protect their ears from Silver Banshee, when they get a call from James. Livewire and Silver Banshee kidnapped Cat. Livewire suddenly appears on all the screens at the DEO, telling Supergirl and The Flash to come to the park if they want to save Cat.

Livewire shoots off her electricity in the park, clearing the crowds away from where she and Silver Banshee have Cat handcuffed to a bench. Livewire threatens Cat, who begs for her life. Livewire can't believe Cat would beg, but Cat is sincere, not wanting her sons to be left without her.

Supergirl and The Flash show up. Silver Banshee screams at them, but the earplugs work. Livewire climbs the electric wires of a building to the roof, and The Flash follows quickly. They fight, with her eventually knocking him out.

Meanwhile, Supergirl frees Cat before fighting Silver Banshee. The crowd continues to watch the fight, which Livewire quickly rejoins. Seeing a helicopter overhead, Livewire aims at it. Supergirl flies in front of the copter and takes the blow. She falls to the ground, weakened. Several members of the crowd step in front of Supergirl, protecting her. Livewire points out that they hated her yesterday. But they were moved by her efforts to protect them and refuse to move. Livewire doesn't care, and plans to hit them all, when she is suddenly doused with a huge stream of water. She loses control of her electricity and accidentally zaps Silver Banshee. Both villains go down.

It is revealed that the water came from a firehose, operated by the same firemen who Supergirl helped a few weeks back when she was exposed to red kryptonite. One of them goes up to her and explains it was their turn to help her. The Flash joins them, only to realize the fight is over.

Once more, the news loves Supergirl, as is seen on the screens at CatCo. Winn, James, and Kara discuss how Barry shoed the police how to incarcerate metahumans like Livewire and Silver Banshee. Kara credits James for teaching her that even bad guys deserve justice. Cat walks up to them, and reveals that she knew all along that Barry was The Flash, and strongly intimates that there is no hiding who you are from her by pretending to be normal.

Back in the field, Barry explains that if he and Kara both run as fast as they can and she then throws him, it should make enough speed to create a breach for him to go back home. He also advises her to go for it with James. They hug, and then race, ending with her flinging him through a breach.

James comes to Kara's apartment, and she talks about the multiverse, how the worlds are separate because they vibrate at different frequencies, but if they vibrated the same, they could be together. Kara kisses him, but James does not react at all, just stares with a blank face while she freaks out. Then he walks from the apartment, still not speaking.

At Non's hideout, it is reported that myriad is now in effect. Non is pleased that Astra's plan is happening.

Back at Kara's apartment, she looks out the city onto the street. Hundreds and hundreds of blank faced people walk in unison. Like an army.

Have you seen Dawn of Justice yet? If so, go rate it in the ComicBook.com Movie Database for a chance to win your very own Armored Batman figure!

Batman v. Superman: Dawn of Justice is now playing in theaters.

Disclosure: ComicBook is owned by CBS Interactive, a division of Paramount. Sign up for Paramount+ by clicking here.