On the Nov. 9 episode of Supergirl, Kara tests her powers against one of Superman’s greatest enemies. Can she succeed where Superman has failed?
Supergirl is interviewed by Cat Grant and accidentally spills that Superman is her cousin. Kara leaves immediately so she won’t tell any more secrets.
The next morning, Kara gets breakfast at a coffee shop with her sister. James comes in to get coffee and Kara laughs too hard at his bad joke making Alex realize that Kara likes him. Alex reminds her to stop telling people who she really is for safety’s sake. The television in the café mentions that Supergirl is Superman’s cousin. Kara looks sheepish.
At the office, Winn asks Kara what she was thinking. She says Cat tricked her. Cat calls Kara to her office. Kara asks her if she thinks Supergirl wanted her relationship to Superman to remain a secret. Cat says she’s writing an expose on Supergirl to be published in her magazine. Kara is to plan a party around it.
A horribly scarred man watches the Supergirl story on the news. He puts on mechanical armor and shoots a nuclear fireball at the television.
Hank reprimands Kara at the DEO for giving the interview. Alex asks her why she gave the interview. Kara said it was to help James and also to help her figure out who she really is. An agent calls a code grey. There’s a multiple car collision, but no sign of alien activity. Kara heads out immediately.
At the scene of the accident, Supergirl helps a bus driver get out of her vehicle. After putting her on a stretcher, Kara is hit with a fireball. She gets up and asks the man what he wants. He says he wants Superman to suffer by losing everything. Kara fights him, damaging his suit. He can no longer shoot fire, so he flies away before she can capture him.
Hank says the Daily Planet called this villain Reactron. They don’t know who he really is, but he’s been trying to kill Superman. They’ve had many public fights with neither coming out on top. Kara asks Hank how they stop him, but he says they don’t. Reactron is human, not an alien, so it’s not the DEO’s jurisdiction. Hank tells her to call her cousin for help.
Back at work, Winn asks Kara and James to follow him. He’s set up an unwanted office with high tech computers to help Supergirl fight crime. He’s set up an algorithm to scan the city for changes in radiation from Reactron’s suit. James tries to convince Kara to call her cousin, but she says it will make National City look like an easy target. He says Reactron almost killed Clark once, making Winn realize that Superman is Clark Kent. Kara says she needs to be defined by her own victories and losses.
Maxwell Lord is inspecting a new levitating train at his laboratory when Reactron breaks through the ceiling. Reactron says he’s looking for someone with a background in nuclear fission and grabs the lead scientist. Max convinces Reactron to take him instead. Kara sees the break-in on the news and heads for the lab. They tell her Max was taken.
Twenty-four hours later, Maxwell is still missing. Kara has no idea how to find him. She distractedly continues to make party plans. Alex visits and offers her help finding Max. Winn takes them to the new office.
Alex scanned the highway with the DEO satellite and isolated Reactron’s nuclear signature. She says it’s powered by an element that can only be found in one place – a nuclear power station where terrorists tried to start a meltdown five years ago. Superman prevented the core from going into overload, but two engineers supposedly died – Ben and Melissa Kroll. Ben Kroll somehow survived the radiation and became Reactron in order to take revenge on Superman for letting his wife die.
Kroll is holding Max prisoner in a junkyard. Max tells Kroll he could help find a way to heal him and let him live a normal life. Kroll says he had a normal life, but it didn’t work out. He tells Max to repair the suit or he’ll kill him.
Kara comes in to Cat’s office saying she read the Supergirl article. In the article, Cat says that Supergirl embodies the worst traits of the Millennial generation. Kara tells Cat that Supergirl isn’t like that. Cat says when Supergirl ends up in hot water, she’ll call her cousin like other Millennials call their parents to bail them out. Kara says Supergirl just needs a chance to prove herself.
James comes in and makes an excuse for Kara to leave. Once they’re outside, he says Winn found a specific mold that grows after a nuclear accident. He’s tracked Kroll to the junkyard. James tries to convince her to just save Max and not fight Kroll. She tells him that Kroll is human and she’ll talk to him like she’d want to be spoken to. If that doesn’t work, they’ll fight.
Kara finds Max in a building at the junkyard. When she unties him, Kroll shoots her with nuclear fire. Max runs off. Kara tells Kroll that his wife wouldn’t want him to hurt anyone. He says Ben Kroll is dead thanks to Superman. He wants Superman to lose someone too. They fight and Kara loses. She ends up passing out right after seeing her cousin step in to save her.
Kara awakes in her apartment a few hours later, looked after by her sister and James. James says Superman had to go. On the news, Max thanks Superman for saving him. Kara asks how Superman knew she was fighting Kroll and James admits he called him. She says it feels like James doesn’t believe in her and asks him to leave. On his way out, he says he’s sorry she’s mad, but he’s not sorry she’s still alive. Kara tells Alex she is supposed to save Superman, not the other way around. How can she become a hero if Superman has to keep saving her? Alex says someday she’ll save him. Kara realizes she’s supposed to be at Cat’s party. Alex gives her a dress she picked from the DEO closet.
At the party, Cat sees Kara and asks her where the magazines are for framing. Winn says Kara was up late autographing the magazines with Cat’s name. Cat is appeased and walks away while Kara thanks Winn. Winn asks her for a dance. She agrees.
Cat approaches Max and says she’s surprised he came. He asks her to dance. They flirt while they move. He asks how she managed to interview Supergirl. Cat says she flew straight to her because she knows she’s powerful. On that note, Cat leaves the party early.
Hank is wandering a hallway at the DEO. His eyes glow red and he says Alex’s name. He finds her in her office and asks what she’s doing. She admits she’s helping Kara. She says she can no longer differentiate between humans and aliens, especially when her sister’s life is at stake. He asks who else knows and she says no one. He says he wouldn’t want them getting any ideas and then asks how they can defeat Reactron.
James asks Winn if he can cut in. James tells Kara he doesn’t like how they left things. He says calling Superman had nothing to do with her. He calls him when he gets scared. He was afraid he was going to lose Kara. She says he has to care enough to let her fly her own path and trust in her. Reactron breaks through the roof looking for Supergirl.
Kara runs off to change and Reactron approaches Max. As Supergirl, Kara knocks Reactron aside and tells Max to get somewhere safe. Kroll shoots down a stone support beam that almost crushes Winn, but Kara catches it. He’s tries to shoot her while she’s busy, but James steps in. He tells Kroll that he’s Superman’s best friend and Kroll should start by killing him. James runs off with Reactron in pursuit.
Alex and Hank call Kara and tell her that she can deactivate the suit by pulling out the core, but it has to be surrounded in lead, to keep it from having a nuclear meltdown. She melts a statue and sticks her hand in the molten lead to dry.
Kara flies outside and knocks Kroll to the ground so James can get away. Kroll throws her and starts to shoot her with a fire beam, but she uses her free hand to deflect it. When he gets close enough, she uses her lead hand to yank the core from his suit. He collapses. Kara tells James he could have been killed. He says he knew she’d save the day.
At the DEO, Kara thanks Hank and Alex for helping her. Hank says it won’t be the last time. Alex asks what Kara wants to do to celebrate. Kara suggests a movie, but Alex tells her to go find James.
Kara goes to James’s office to talk to him, but he’s not alone. Lucy Lane, his ex-girlfriend, introduces herself. She’s Lois’s little sister. James says he’ll catch up with Kara later. When she leaves, Lucy tells James that she doesn’t like the way they ended things and asks to take him to dinner. He agrees. Kara is crushed.
On Kara’s computer, she finds an instant message from Clark. She thanks him for saving her. He says it won’t happen again. He tells her she’s doing great and she thanks him.
Alex and Kara get together for Chinese food at Kara’s apartment. Alex read Cat’s article and tells Kara that beneath the disdain, Cat respects Supergirl. Alex is proud of her for doing things even Superman couldn’t do. They hear a siren and Kara takes off to help.