The episode opens on DEO guards escorting a humanoid-looking alien with facial features like something out of Babylon 5 through the corridors in chains.
The alien breaks his chains and, after knocking out the guards, tears into the main control room before Supergirl comes to incapacitate him. During the fight, she gets a call from Alex, who is frustrated because Kara promised she would be there. Kara tells her that she will be, and then continues the fight. When she finally bodyslams the alien and tells Henshaw that "he was tough," Henshaw tells Supergirl it's a she. Kara asks for the rest of the day off.
At Alex's apartment, she's freaking out. She's worried that her mother will be upset that Kara has come out as Supergirl -- but when Eliza comes in, she's happy to see Kara, and she's proud of her. She's still a little less impressed by Alex.
Leslie Willis, a deejay, is broadcasting from a basement, complaining about Supergirl -- much to Winn's and James's annoyance. Even Cat is unimpressed, switching off the radio.
At the office, Kara and Winn are talking about their Thanksgiving plans: Winn is going to go home alone and watch Orphan Black. Kara says he has to come to her place instead.
Cat has pulled Willis into the office and tells her to leave Supergirl alone. When Leslie objects, Cat tells her that she's being transferred to the traffic chopper becuase Cat isn't willing to buy her out of her contrac to fire her. Willis warns her against it, then leaves as the lights flicker.
At a bar, Kara invited Jimmy to the Thanksgiving dinner, but Jimmy has plans with Lucy out of town.
Alex comes, and is still worried about her mom. Kara tells her she should tell her mother about her job at the DEO but Alex says absolutely not.
Willis's traffic chopper hits turbulence, and the pilot wants to turn back but Willis refuses. When it starts to spin out of control, Supergirl saves it -- but when she takes Willis's hands, a bolt of lightning hits both of them.
At the hospital, Cat feels guilty for having put Willis in the traffic chopper, although she doesn't want to admit it to Kara. Before leaving, she tells Willis to get up.
At Alex's apartment, Eliza tells her to turn the TV off. She tells her she doesn't understand how Alex can allow Kara to put on the costume. She says she thought she could count on Alex to look out for Kara. Alex leaves to go back to work.
In a flashback, Eliza brings Jeremiah Danvers inside, and as soon as they're gone, Kara takes Alex out for a flight.
Back in National City, Eillis is out of the hospital and walking around with lightning coming off her hands. When a man accosts her in an alley, she unconsciously blasts him with electricity and gets a rush from it.
At Thanksgiving dinner, things are awkward between a drunk Alex and Eliza, who is obviously a big fan of Kara. Kara leaves the table to take a quick call from James, who says he's stuffed and a little bored. Kara tells him to have fun with Lucy, and he says happy Thanksgiving.
Back at the table, when Winn starts asking Eliza about work, which prompts Alex to come clean about the DEO. Eliza chastises her, including questioning whether she thinks Jeremiah would be proud of this.
After Alex and Winn leave, Kara asks Eliza why she's always been so much harder on Alex than on Kara. Before Eliza can answer, Kara gets a call from Cat that she has to answer.
In the flashback, Jeremiah yells at the teenage girls for going on a flight. As they're being yelled at, there's a knock at the door and Jeremiah tells them to go upstairs. He answers the door, and it's Hank Henshaw.
At CatCo, Cat has a conference call to Beijing and nothing is working. Kara tries to work on the computer, but when Kara says she thinks they need Winn, all the lights go out. Leslie, now calling herself Livewire, is broadcasting straight to Cat's TV bank in her office. She then appears in front of Cat, and starts firing off electricity. Kara rushes Cat into a corner to hide, and then Cat sends her twenty floors down to get security. As Livewire confronts cat, Supergirl jumps in front of a blast, offering to help Leslie. During the fight, Livewire feeds off Supergirl's vision powers, and then attacks an elevator Cat finds herself in. Supergirl flies down the elevator shaft to save Cat.
At CatCo, Henshaw and Kara watch coverage of Livewire-related blackouts. Henshaw figued out that it wasn't the lightning, but the way the lightning got focused through Kara's body, that created a supervillain. They strategize about how to beat her, with Henshaw offering up a weapon from the DEO's armory.
After Henshaw leaves, Cat tells Kara to go home. After a brief talk with Cat about mothers and daughters, in which Cat reveals she is who she is because of her disapproving mother, Cat says she feels like it's her fault Leslie became Livewire -- that she rewarded Leslie's bad behavior instead of holding her to a higher standard because it gave them ratings.
At home, Alex goes to check on Eliza, who apologizes for what she said about her dad -- that Alex always makes the hard choice. Alex asks why Eliza was so hard on her, and not on Kara. Eliza said she just wanted Alex to be better than her, but that didn't mean she didn't love her -- that Alex has always been her supergirl. Alex apologizes for lying about the DEO, and Eliza says there's something she needs to tell both of the girls. Before she can say anything more, Alex gets a call and goes to take care of something at work.
At CatCo, Cat is drinking wine when Supergirl arrives. Cat says she'll help draw Livewire out if Supergirl will help her catch the baddie.
At the DEO, they give Kara a trap to use against Livewire.
At CatCo Plaza, Cat broadcasts, calling out Leslie. She invites her to "where it all started," and they meet in the stret where Cat had discovered Leslie. After briefly trying to reason with her, Livewire blasts at Cat. Supergirl comes to the rescue, and while Livewire briefly gets the best of her, making it impossible to use the DEO's trap, Supergirl touses her with water from an underground pipe, knocking Livewire out.
Back at CatCo the next day, she gives Winn leftovers. Winn admits that his father is a terrible person, who's in prison, and he's grateful for having been included in her holiday. He kisses her on the cheek. Just then, James and Lucy show up. James asks if she's okay, how Kara is doing, and she says she's glad to have him back.
She heads into Cat's office with a number of paparazzi photos. Cat opts instead to run some positivity with a photo essay on people who volunteered at soup kitchens. As Kara goes off to take care of that, Cat tells her that after learning about her parents' death and her life with a foster family, Cat wants to know more about her.
At home, Eliza Danvers tells the girls that Jeremiah's death wasn't in a plane crash, that she never believed that even though it's what "they" told her.
In a flashback, Henshaw and company want to take Kara away. Jeremiah instead offers himself up to work for the DEO. He knows everything there is to know about Superman, and he'll turn over that research but they have to leave Kara alone. Henshaw tells him, "Welcome to the DEO."
Eliza tells them that her husband died working for Henshaw.
Back at the DEO, Henshaw congratulates Kara on her capture of Livewire. Both of the girls stonewall him, and Alex says they have to find out what happened to Jeremiah. Kara agrees.