Kara teams up with her former friend Lena to try and stop Lex and Leviathan. Meanwhile William is in danger and held prisoner by Eve.
Tropes:
- An Offer You Can't Refuse: Gamemnae makes it clear that Andrea has no choice in killing Supergirl, threatening her father's life.
- Apologetic Attacker: Eve is very sorry about having to shoot William.
- The Atoner:
- Lena is out to make up for her crimes, and, while naturally hesitant, Kara eventually comes around and the two of them start mending their relationship.
- Also Brainy, realizing the full extent of his mistake to ally with Lex, decides to stop putting up with his bullshit and try and sacrifice his life to save his friends.
- Big Bad Duumvirate: Lex is shown working together with his mother Lillian during The Stinger.
- Call-Back: "Reporting 101. When you get kidnapped, you know you're on the right track."
- Cliffhanger: The episode (and due to the Pandemic, the season) ends with Gamemnae being revealed to be Not Quite Dead and forsaking her human disguise, while Lex meets up with Lillian to use the shrunken Leviathan members for an unknown purpose.
- Cooldown Hug: After convincing Andrea not to kill Supergirl, Lena pulls her friend into a hug.
- Cut Short: Due to filming of episode 20 being abandoned, this now becomes the season finale.
- Easily Forgiven: Subverted. Kara does believe Lena's remorse and guilt are genuine. But after everything Lena did throughout the Season, Kara's also understandably not in a forgiving mood; she outright tells Lena she can't give her absolution. They only finally take the first steps to bury the hatchet in order to stop Lex — but it's still clear it's going to take a lot of time and effort to rebuild their friendship.
- Evil Cannot Comprehend Good: Lex admits that he didn't actually expect Brainy being willing to kill himself to stop Leviathan even if he foresaw the possibility.
- Evil Is Petty: Whatever J'onn said to provoke Rama Khan enraged him enough that Rama Khan decides that, once Leviathan is done with Earth, he wants to go after Mars next.
- Faux Affably Evil: Gamemnae starts out friendly as ever while asking Andrea to repay Leviathan's favors, only to quickly move to threats when Andrea hesitates at the idea of assassinating Supergirl.
- Flat Character: Tezumak and Sela basically act as supporting muscle for Rama Khan; neither has any lines and the audience gets no sense of their personalities.
- Friendship Moment: Lena and Kara make their first steps towards fixing their friendship at the end of the episode.
- Forgiven, but Not Forgotten: Kara's guilt over lying to Lena only goes so far; while willing to accept her help, Kara is still angry about Lena's long list of crimes against her, and eventually tells her off for it.
- From a Single Cell: Rama Khan, Sela and Tezumak regenerate from piles of ashes.
- Glamour Failure: Gamemnae briefly shows her true form when Lex catches her communicating with the mysterious leader of Leviathan, and after her plans are foiled, her human skin is completely blown off, revealing the robotic form underneath.
- Go Through Me: Lena doesn't let Andrea pass through her to kill Supergirl.
- Heal It With Fire: Supergirl cauterizes William's gunshot wound with heat vision so he won't bleed out before they get to the hospital.
- Heel–Face Turn: Lena cements hers here, protecting Kara's identity in front of William, and saving a helpless Kara's life when Andrea is sent to assassinate her.
- Heroic Sacrifice: Brainy marches into Leviathan's ship to bottle them, knowing that he'll end up succumbing to the ship's radiation field.
- Heroic Second Wind: Kara, after getting the Kryptonite suit and her friends coming to her rescue, proceeds on turning the tables on Rama Khan, Sela and Tezumak. Unfortunately, they promptly regenerate.
- Heroic Willpower: Brainy manages to hang on and complete the shrinking process despite the strong radiation field causing him great agony.
- Hidden Villain: Compared with Greater-Scope Villain. Gamemnae answer to a mysterious, female superior.
- In the Hood: As a vigilante, Alex copies Green Arrow's costuming style, including his hood.
- Internal Reveal:
- Andrea learns about Gamemnae being a part of Leviathan and gets her powers activated.
- Nia learns that Brainy has been working on defeating Leviathan after receiving a clearer vision, when she previously suspected him of being in cahoots with them.
- I Shall Taunt You: J'onn psychically insults Rama Khan to draw him out while Supergirl talks everyone out of Obsidian VR.
- Last Episode, New Character: The other two members of Leviathan (Tezumak and Sela) are finally introduced, but neither has any lines. Not to mention, they all have a boss we don't get to know just yet; presumably that's for next season.
- Left for Dead: Brainy is left to die due to his radiation exposure, while Lex makes off with the canister containing the Leviathan members.
- The Man Behind the Man: It is once again brought up that there's a true leader of Leviathan above Gamemnae, who remains The Unseen for now.
- Mundane Solution: Kara and Lena get around the problem of Kara not being able to use her powers without alerting Rama Khan to her location by simply taking the bus to L-Corp.
- Nice Job Breaking It, Hero: Lex reveals to Brainy that he anticipated his conscience wouldn't allow him to kill Supergirl and he was counting on him shrinking down the members of Leviathan for an unknown purpose.
- Not Quite Dead: Gamemnae seemingly overloads and crashes when Brainy bottles the other Leviathan members, only to get back up shortly after.
- Playing with Fire: Tezumak has the ability to control fire.
- Pop-Culture Pun Episode Title: To Mortal Kombat.
- The Power of Trust: Three scenes of trust are shown back to back. The female Brainiac 5 shows Brainy she trusts him, while Lena does the same with Andrea and Supergirl does with the people in the virtual reality.
- Pragmatic Villainy: When Supergirl tries to talk everyone out of Obsidian VR, Gamemnae panics and wants to hit the kill-switch early. Lex talks her out of it because unless they hit at least 50% saturation, the remaining human population will immediately turn on them, not to mention the fact that she'll be seen as a failure by her boss.
- Properly Paranoid: Rama Khan activates the ship's radiation field and keeps it up when Lex is shown the ship, as he doesn't trust that others may find their way to it now that Lex knows.
- "The Reason You Suck" Speech: Kara tells Lena off for her previous duplicity and attempt to follow up on the Non Nocere project even if Kara hid her identity from her to protect her from being targeted. While understanding of her being sorry, Kara told her she wouldn't absolve her.Lena: Please Kara, I'm sorry. Okay, I truly believed what I was doing was helping people.Kara: I told you I don't want to talk about the past.Lena: Oh, come on, you can scream at me if you like. I know I deserve it. I know now that working with Non Nocere was a mistake. That working with Lex was a mistake.Kara: This isn't about Lex! This is about J'onn and Alex and all the other people that could've been killed today because they are on my team. Don't you understand that?Lena: No, I do. Of course I do.Kara: No you don't. You have never understood what it means to share a secret identity with someone. How much danger that puts them in. You never even understood that I kept my identity from you because I wanted to protect you! And I know, I know that I hurt you by waiting so long to tell my truth, but what about all the ways you hurt me? You pretended to be my friend for weeks just so you could manipulate me. You stole from me. You convinced me to steal for you. And then, then you even, you used Kryptonite on me. I made one mistake, one mistake that was only ever meant to protect you, and in return, all you did was hurt me in every way imaginable.Lena: I'm sorry.Kara: I know you are. But if you came to me looking for absolution, I can't give it to you.
- Shock and Awe: Sela has the ability to control lightning.
- Shout-Out: Nia compares the decoy plan to the opening of Harry Potter and the Deathly Hallows; Kara isn't impressed, since Hedwig and Mad-Eye Moody both died during the plan in the book.
- Shrink Ray: Brainy shrinks down Rama Khan, Sela and Tezumak, possibly at the cost of his own life due to the ship's defense mechanism.
- Skyward Scream: After Gamemnae awakens from almost being killed by Brainy's shrink ray and sees her plan go up in smoke she burns out of her human form and screams in pure rage.
- Spotting the Thread: William is very quick to notice that Eve is Trapped in Villainy and tries to appeal to her. Unfortunately, she still (albeit reluctantly) proceeds to shoot him, and had Supergirl not saved him, he would've died.
- Take Our Word for It: The audience doesn't hear the telepathic message J'onn sends to Rama Khan, but whatever it was, it definitely succeeded in provoking him.
- Talking the Monster to Death: Lena manages to talk Andrea down from killing Supergirl.
- Throw the Dog a Bone: Poor Eve finally manages to get something of a happy ending, with her mother being rescued.
- Trailers Always Spoil:
- Set photos gave away the fact that Lena and Kara would team up months before the episode aired.
- Jon Cryer said in an interview several weeks before the episode aired that due to the production shutdown, the scenes with Lex being defeated weren't filmed and as a result he gets away with his plans.
- Uncertain Doom: Lex leaves Brainy for dead on Leviathan's ship, but the episode ends before confirming Brainy's fate one way or the other.
- Villain Ball: Surprisingly, Lex of all people grabs it when he leaves Brainy to die (i.e. leaving the possibility that he still might survive somehow) of the radiation in Leviathan's headquarters instead of finishing him off while he's weak.
- Villainous Breakdown:
- Gamemnae has a huge one at the end of the episode, after she almost dies and realizes her plans are ruined with her burning out of her human shell and screaming into the air as the TV's behind her explode.
- Lex has one when he realizes that Brainy shrank Leviathan before they could kill Supergirl with him screaming at him that they were so close to killing off all immortal aliens. He quickly calms down though after taking the shrunk Leviathan members and just notes that he will kill Supergirl himself.
- We Need a Distraction: Since Rama Khan can sense Kara wherever she goes the Superfriends decide to have J'onn and M'gann shapshift into Supergirl and distract Leviathan so that she and Lena can get to her lab so Lena can build a new Kryptonite suit.
- What Happened to the Mouse?: After Lena talks her down, Andrea disappears.
- The Worf Effect: Kara and her friends are hopelessly outmatched by Rama Khan, Tezumak and Sela, who will endlessly regenerate no matter how many times they're "killed", and are basically only able to distract them. Had Brainy not shrunken them down, the three would have killed them.
- Xanatos Gambit: Lex anticipated that Brainy wouldn't stick to the plan and would instead shrink Leviathan. Once Brainy does so, Lex shows up and takes the canister so he can use it to kill Supergirl himself.
- You Are Better Than You Think You Are:
- Both Alex and Lena encourage Supergirl that she is strong enough to wake up billions of people from Obsidian Platinum.
- Kara then proceeds to encourage all the users to be stronger and resist the temptations of the program, successfully waking them all up.
