Aboard the Daxamite flagship, Superman grabs Supergirl and throws her across the bridge. He says that they are his people and he won't let her harm them, and Supergirl slams him back. Rhea explains that she used Silver Kryptonite against Superman when he came after her. She explains that Superman sees his worst enemy, Zod, when he looks at Supergirl. Supergirl tries to get through to him, but he unleashes his heat vision and she uses her own to block his blast.
Superman slams into Supergirl and knocks her into a building in the city. When she tries to help two bystanders, Superman throws her away. Outside, he grabs her and carries her into space.
At the DEO, Alex registers Superman's presence on the scanners. They arrive as Supergirl and Superman slam back into the city. The two cousins punch each other repeatedly, and Supergirl finally knocks Superman out. Alex runs to her sister, assuring her that she's there.
Kara wakes up to Mon-el in bed and she talks about the necklace that her mother gave her before she sent her to Earth. She suggests that they stay in bed a little while, and Mon-El tells her that she's in the Fortress.
Gasping for breath, Kara finds herself lying in the Fortress, next to Superman. Alex is there and tells her that she passed out and Alex brought both of the Kryptonians there. Superman wakes up and is back to normal, and Supergirl hugs him.
Lena is in her apartment drinking when Lillian comes in. Lillian wonders how Lena let Rhea fool her, and Lena says that she was desperate enough for validation to take it from the first mentor she found. Her mother apologizes and says that she wanted to be a better mother to her. However, every time she's had a choice to choose something else, she's chosen that. Lillian admits that she has justified the worst behavior for the best causes, but points out that her concerns were real. She suggests that she might have been wrong supporting the wrong child to stop the aliens. Lillian hands her a metal box and explains that Lex created it to destroy Superman. If Lena can adapt it then she would be the Luthor who saved the world.
At the Fortress, Supergirl tells Superman what happened. He points out that he was at full strength and Supergirl beat him, and Supergirl says that they have to figure a way to defeat rhea. They ask Superman if he has a weapon, and he says that there is something in the archives about the early wars with Daxam. They find a reference to Dakkam Ur, and Superman says that it's old but it might work.
Later, the trio returns to the DEO. Mon-El introduces himself to Superman, who figures that he's a good guy if Supergirl is with him. Winn tells them that J'onn is unconscious but stable, and they've cleared all Daxamite soldiers from the building. Supergirl tells them about Dakkam Ur. Mon-El objects, but Supergirl warns him that it's the only weapon they have. An alarm goes off as the Daxamite ships charge up, and Supergirl tells Winn to contact Rhea.
As Rhea prepares to fire, Supergirl contacts her and invokes Dakkam Ur: a trial by combat between just the two of them, for the fate of her people. Rhea accepts her challenge and says that they duel in four hours. The ships power down their weapons, and Mon-El says that Supergirl is going to end it. He asks why Superman can't fight it, and Superman points out that Supergirl just defeated him and she's the champion of Earth. Supergirl tells Mon-el that she needs him strong.
J'onn lies in his coma and Megan comes in and says that his friends need him because the great fight is coming. When he worries that he isn't strong enough, Megan kisses him and tells him to wake up... and Hank wakes up. He tells Alex that Megan was there, and Alex starts to bring him up to date.
Supergirl watches the newscasts about Dakkam Ur, and Hank comes in and says that they need to contain it. He tells them that they don’t want an army of innocent civilians around when Supergirl fights Rhea.
At CatCo, Cat is in her office writing stories. Kara and Clark come in and Clark asks how he can help. Cat tells him to talk some sense to James because he's been going around fighting the Daxamites. She wonders where Kara has been, and tells her to go out and report. Kara says that Supergirl gave them an exclusive interview in return for Cat toning down the sensational tone of the battle. Cat says that people are finally starting to stand up, and Clark turns on the charm to convince her. The CEO asks Kara if she thinks Supergirl is ready for it, and Kara says that Supergirl told her that she is. Cat tells them to go out and tell Supergirl that they're all rooting for her. As they leave, they get a request to see them.
Supergirl and Superman fly to L-Corp and find Lena and Lillian waiting for them. They explain that the device would radiate the atmosphere with kryptonite. Lena says that she can convert it to irradiate the atmosphere with a trace amount of lead, enough to make it toxic to Daxamites. Even Mon-El would have to leave Earth, and Supergirl tells them to start working.
Back at the DEO, Supergirl and Superman tell the others about the device. Mon-El tells them to use it if Supergirl, and Supergirl insists that they won't have to use it because she's going to beat Rhea. Hank sends Winn to L-Corp to assist the Luthors, and Mon-El says that he's going with Supergirl to be her second when she fights Rhea. Supergirl asks Superman to spar with her until the fight.
In the training room, Supergirl tells Superman that if she beats Rhea then she gets to keep everything that she's built for herself and wanted. Superman tells her that he's always fighting for Lois in his heart, and the people they love are another superpower. He tells his cousin to keep them with her and they hug.
Supergirl and Mon-El fly to the rooftop and Rhea and her second teleport in. They confirm the sakes of the Dakkam Ur, and the two women charge at each other. As Supergirl takes Rhea down, Daxamite fighters open fire on the city. Rhea says that her gods are only concerned with her victory, and Supergirl tells Mon-El to go and be a hero. After a moment, he takes off.
Hank changes to his Martian form, and he and Superman fly off to help the people.
Rhea invites Supergirl to hit her, and Supergirl does so. Rhea reveals the kryptonite in her body and says that she's carried it across galaxies.
Winn and Lena finish the device, and Lillian tells them to end it on. When Winn objects, Lillian shoves him aside and takes the device. Lena explains that she gave the remote to Supergirl, and suggests that they call the DEO to notify Supergirl.
Daxamite soldiers attack Mon-El, who takes them down. Meanwhile, Superman and J'onn are getting the people to safety when more Daxamites teleport down. Alex tells Superman that more soldiers are attacking the hospital.
Rhea knocks the weakened Supergirl through the building and back up to the roof. The queen sees Superman using his heat vision on the Daxamite ships, and tells her second to get Superman.
Cat and James look out on the city from Cat's office. The Daxamite knocks Superman in through the window, and he knocks him out of the building.
M'gann knocks the soldiers attacking J'onn aside. White Martians land and M'gann says that they're friends. The Martians attack the Daxamites.
Supergirl continues fighting, but Rhea punches her and says that she will destroy city after city until Earth is gone. The Kryptonian catches her next blow and fights back despite the Kryptonite, and promises that she is going to protect her world. Rhea says that they will keep coming whether she lives or dies. Mon-El arrives and Alex tells Supergirl that the Daxamites have locked on to every school and hospital in the city. Supergirl looks at Mon-El, who nods. She takes out the remote and apologizes to Mon-El, and then pushes the button.
The Device activates and lead sprays into the atmosphere. Rhea and the invading Daxamites start choking, and the soldiers quickly teleport up to their ships and fly into space.
Mon-El starts to choke, and Rhea begs him to save her. He reminds her of how she killed Lar, and Rhea calcifies. Supergirl asks Alex what to do, and Alex tells her that the entire atmosphere has been infected. Mon-El tells Supergirl that it was worth it, and Supergirl asks Alex to do something for her. She then takes Mon-El to the survival pod. Mon-El tells her that wherever he goes, he'll be better because of her. He promises that he's going to be the man that she thought he could be, and Supergirl tells him that he's made her so happy. She gives him her necklace to keep him safe and says that she loves him. They kiss and Mon-El then gets in the pod and leaves Earth.
That night at the DEO, everyone celebrates. Supergirl looks out on the city and Superman joins her. He says that he has to get home, and Supergirl insists that she did the right thing. Superman admits that he's humbled by her and doesn't think that he could have made the same choice. He tells his cousin that she's stronger than he ever will be, and flies off.
Megan tells Hank that there are a lot of White Martians who agree with her philosophy. She says that she felt him fall away mentally, and they kiss. Megan says that she can stay for a while and they walk away.
Alex joins Supergirl and tells her that she felt broken. Then Supergirl forced her way into her home and told Alex that she was proud of him. Alex says that it was something to hold on to, and tells Supergirl that she's proud of her. Supergirl tells her to be with Maggie, and she doesn't have to act like everyone else's world has stopped. Alex asks what Supergirl needs that moment, and Supergirl tells her to never let Maggie go before flying off. Maggie comes out and hugs Maggie, and assures her that Supergirl will be okay. Alex asks Maggie to marry her, and Maggie smiles.
The next morning, the news reports that Lillian is taking responsibility for ridding National City of the invaders. Kara visits Cat and wonders why she's frowning. Cat is amused when Kara says that she had a boyfriend, and Kara explains that it didn't work. She thought that she could have a happy relationship but is beginning to wonder if that will ever happen. Cat tells her that the pain will go away eventually, and says that what makes women strong is that they can feel vulnerable. She says that Kara has accomplished great things with her articles, and her prose has improved. Cat assures Kara that she's on a hero's journey, and will soar over it just like she would. Sirens sound in the distance and Kara says that she has to go. She thanks Cat and walks out, and Cat tells Supergirl to go get them.
Outside, Kara changes into Supergirl and flies off.
Mon-El flies through space, looking at Kara's necklace. A rift in space opens before him, drawing the survival pod in.
35 Years Ago... The Day Krypton Died
Kal and Kara are launched into space. Elsewhere on the planet, a group of robed Kryptonians place a baby into a third pod. One of them feeds the baby a bit of their blood. They confirm that "it" should survive the journey and grow strong on Earth, and then it will reign.
Written by Gadfly on May 24, 2017