Supergirl, Mon-El, and the DEO go to Julia Freeman's house and surround the place. Winn confirms that there's one heat signature inside, and Supergirl kicks down the front door. The DEO goes in and Winn says that Julia is in a back room.
Hank and Mon-El find Julia singing along to her headphones. Supergirl recognizes Julia from her dream of the Worldkillers, and gets her attention. Julia recoils in fear, wondering why they're there, and Supergirl tells the others to stand down. She realizes that Julia doesn't know why they're there, and Julia begs her not to let the DEO hurt her. Alex aims her gun and tells Julia not to move, and Julia transforms into Purity and unleashes a blast of sonic force. The house explodes around the team, and Mon-El saves one agent from a fling poker. Purity unleashes sonic screams at the agents, and Supergirl blocks her with a wall of ice. Hank passes through the wall, and when Supergirl shatters the ice, they realize that Hank has put power-dampening handcuffs on Purity.
Sam finds Lena at her L-Corp desk, and Lena says that she can handle things at L-Corp. Her friend figures that Lena doesn't believe that she's up for the job, and Lena assures Sam that she doesn't have to keep proving that she's good at job. She orders Sam to take the day off and be with Ruby.
At the DEO, Winn shows the others the Kryptonian data cache crystal that they found in Julia's home. They figure that they can use it to pinpoint the Worldkillers' headquarters, and Mon-El asks Supergirl if she's okay. Winn says that Purity's sonic blasts are specifically designed to work on Kryptonians. Alex figures that Supergirl is off and suggests that they run tests. Once the others leave, Supergirl says that it's not the sonic blast that's bothering her.
Mon-El asks Hank to loan them a part from his spaceship to fix the Legion cruiser. Winn wants to see it, and Hank reluctantly agrees.
Supergirl tells Alex that Julia asked her for help and was scared, but Alex figures that Julia was lying to get close enough to Supergirl. Her foster sister suggests that if she can get Purity to become Julia again, and Alex agrees but says that when it fails, they'll do it her way.
Supergirl and Alex enter the brig and Supergirl tries to get through to Julia. Purity says that "Julia" isn't her name, and insists that she is justice. Supergirl says that she'll call her Julia and wants to talk to her, and Purity says that they don't understand yet but Alex does. Alex tells her that Purity might think that she's smarter and smarter than her, but Alex will eventually find out everything about her. Supergirl continues trying to get through to Julia but Alex doesn't think that it can work.
Sam gets Ruby up at school to take her ice skating.
Hank takes Winn and Mon-El to the garage where he keeps his spaceship, disguised as a car. Mon-El explains that they need a Moran battery to generate the fuel cells on theirs, and Hank removes it.
Supergirl reviews Julia's birth records and discovers that she's an orphan. Purity says that Julia was fun to play, and there never is a "Julia Freeman". When she and the Worldkillers arrived, they knew that masks would be necessary. Supergirl shows her a photograph of Vinita, her best friend for a decade, and points out that Julia saved her life. Julia emerges for a moment, and then Purity says that she doesn't about humans. She promises to tear out Supergirl's soft parts, and Alex tells her that she'll never get the chance. Purity says that she'll kill Alex next, and Supergirl takes Alex outside to talk privately. She asks why Alex is fighting her, and Alex says that Purity is toying with her. Alex warns that Supergirl's attitude is naïve, and Supergirl's feelings are costing them lives. Supergirl wonders why Alex has become hard and cynical, and Alex tells her that cynicism is keeping the rest of them alive and she's just trying to do her job... and now they're going to do it her way.
On the cruiser, Mon-El installs the Moran battery, and Imra comes in and says that she and Brainiac-5 haven't had any success with an alternative. Mon-El snaps at her and Imra says that she's just speaking the truth. Winn quickly excuses himself, and Mon-El tells Hank that there's no use continuing.
Alex demands to know where Reign is, ad Purity finally chuckles and says that she can see that Alex wants to hurt her because she's hurt and it's not getting better. Supergirl tries to pull Alex away, but Alex angrily tells her to shut up Purity says that Alex had her chance for happiness and lost it, and Alex walks away. Supergirl says that she will make sure that Purity is just a thing and Supergirl won't let her destroy anyone else.
Sam and Ruby continue skating.
Winn goes back to his lab and sees Alex pacing angrily. He hugs her and asks what happened, and Alex insists that she's good. The Kryptonian data crystal glows and Winn goes over to examine it.
Purity mutters in Kryptonian that the Worldkillers will destroy the world, and Supergirl promises to defeat them.
The data crystal continues glowing.
Sam's eyes glow red and she stops. When Ruby turns around to find her, she discovers that her mother is gone.
The crystal flares and burns out the DEO's power. Purity shatters her cell, knocking Supergirl unconscious. She walks through the DEO, blasting anyone in her path, and goes to the workshop to get the crystal. When she grabs it, a blast of energy knocks Winn back. More DEO agents arrive and Winn blasts them and then flies out of the building.
Mon-El is examining the ship specs when Hank comes in with Martian alcohol. He invites Mon-El to join him, and they drink. Hank says that he's familiar with marital spats, but Mon-El doesn't want to talk about it. Undeterred, Hank persists and Mon-El says that he and Imra didn't choose to get married. They married to unite the different planetary factions, and Mon-El was still mourning Kara. Eventually their feelings deepened and Mon-El grew to love Imra. He's had to keep a distance from Kara despite his feelings, and there's been friction between him and Imra. Hank talks about how he and his wife shared their thoughts and feelings, and tells Mon-El that sharing is part of marriage. He advises Mon-El to let Imra in if he loves her. Hank receives a text that Purity has escaped.
Ruby calls Lena, who comes to the rink. They talk and Ruby describes the trip that Sam took and afterward didn't remember. Ruby figures that something is wrong, and Lena assures her that she'll find an answer.
Winn tells the team that Purity is in the subway and Mon-El is glad to help them. Supergirl tells Alex that she isn't underestimating Purity again, and Winn gives them sonic dampeners that will negate Purity's sonic frequencies.
Reign goes to her Fortress, and the Dark Kryptonian says that Purity has awakened and Reign must guide her. However, she warns that Reign must bring Purity to the Fortress before the DEO takes her away.
Purity boards the subway train, still holding the crystal, and hears Kryptonian chanting in her head. As she get sup, Supergirl flies in and Purity tries to blast her. The sonic dampener negates her power, and Supergirl knocks her out of the train and onto the tracks. Alex and Mon-el are waiting and wearing the sonic dampeners as well, and J'onn emerges from the wall. Purity blasts the floor, knocking all of them into the station below. The Worldkiller then attacks the station pillars, forcing J'onn to grab the shattered support pillar while Mon-El and Alex get the bystanders out.
Supergirl and Purity fight, and Mon-El goes to help Supergirl. She knocks him back and then grabs Supergirl by the throat and says that she's going to make Julia watch while she kills her. Supergirl begs Julia not to let Purity hurt her, and Julia briefly regains control. Alex runs over and calls to Julia, saying that she can see Julia inside and tells her to fight. Julia and Purity fight for control of the body, and Julia finally collapses.
Reign flies in and Alex opens fire on her. The villainess shoves Alex to the floor and starts crushing her with her heel. Julia yells at her to stop and offers herself. Supergirl tells her not to, but Reign greets Purity as her sister and says that they will find Pestilence and then they will be unstoppable. Reign flies off with Julia as J'onn finishes restoring the pillar.
Back at the DEO, the doctors confirm that Alex is okay. Winn reports that they lost track of Reign and Julia, and Alex suggests that Julia can hold out. Supergirl suggests that they're supposed to save Worldkillers rather than beat them.
At the Fortress, the Dark Kryptonian tells Julia that she doesn't have to be afraid. Julia freezes, screaming that she doesn't want it, and the hologram tells her that her wakening has begun.
Mon-El returns to the cruiser and finds Winn and Imra working to restore the power source. Winn suggests that Mon-El let him take it out for a test drive. Imra points out that Mon-El didn't call her to the fight, and Mon-El apologizes for how he's been acting. She says that she say the look in Mon-El's eyes when he looked at Supergirl, and it was the same way he looked at Imra the first time he told her that he loved her. Imra wonders if Mon-El is still in love with her, and he admits that he doesn't know. She thanks him for being honest, and Mon-El promise that he will always be honest with her. He says that they'll work through it, and Imra tells him that it's time for her to tell him the truth about why the Legion is really there.
At the bar, Kara and Alex drink and Alex assures her foster sister that they're okay. She says that she thought breaking up with Maggie would get easier, but it isn't. Alex admits that she's scared and weak, and that's why she's lost hope. Kara explains that she got through the heartbreak of losing Mon-El and Alex is stronger than she is, and figures that there is another person out there for Alex.
Sam returns to Lena's office and Lena assures her that Ruby is fine. When Sam wonders if Ruby was scared, Lena says that they all are and asks if she remembers what happened. Sam doesn't, and is surprised to learn that Ruby realized there have been other times. Lena says that she reassured Ruby, but Sam is furious that Lena told her anything. She says that no one makes those decisions but her, and orders Lena to remain silent. Reign takes over for a moment, and they realize that Sam had another blackout. Lena says that she knows what's wrong with her and she's going to make her better.
Written by Gadfly on Feb 6, 2018