Pestilence's plague is unleashed on National City, causing friction between Kara and Imra on how to handle the situation. Meanwhile, Lena is still trying to find a way of exiling Reign from Sam permanently.
Tropes:
- Celebrity Paradox: Played With. Winn made A Nightmare on Elm Street reference and Katie Cassidy (Dinah Laurel Lance) played the Decoy Protagonist in the 2010 remake, and co-starred with Clancy Brown. However, there is yet an Earth-38 Laurel nor a Earth-38 Eiling to appear and the film franchise is yet to be mentioned on the Earth-1 shows.
- Downer Ending: All three World Killers are released and united under Reign.
- Even Evil Has Loved Ones: The World Killers seem quite attached, calling each other sister.
- Evil Cannot Comprehend Good: Pestilence doesn't understand why Supergirl would want to protect innocent civilians.
- The Extremist Was Right: Unfortunately, Imra's approach is somewhat proven as the right one in the end, especially since Pestilence is not an innocent woman forced into evil by her Split Personality, unlike Purity and Reign.
- Failure Hero: Imra tells Kara that the reason why the Blight plagues the future is because Kara failed to stop Pestilence.
- Fish out of Temporal Water: Brainy has no idea what social media is. According to Mon-El, that's because it's a relatively short-lived fad that dies out before the Legion's time.
- From Bad to Worse: M'rynn's dementia has got to point where he and J'onn are having the same conversation every day; occasionally he realizes it.
- Glamour: Brainiac 5 has a personal image inducer that allows him to appear human, briefly freaking out the DEO until he clarifies things. Winn sees right through it.
- A God Am I: Pestilence says this about herself when mentioning that people say surgeons have a god complex.
- Headbutting Heroes: Imra and Supergirl clash a few times throughout the episode, due to their different approaches on how to handle Pestilence.
- Hope Spot:
- For a moment, Supergirl seems to get through to Grace by mentioning her oath to do no harm. Then Grace pivots to how being a surgeon has made her more cynical about the world, making it clear she doesn't want to be saved.
- Lena's experiments bear fruit and she has isolated the mechanism by which Sam changes into Reign. Unfortunately, Purity and Pestilence are on their way, so Lena doesn't have the opportunity to act on it before Sam is taken.
- Internal Reveal: Supergirl and the DEO find out that Sam is actually Reign.
- It's Personal: Imra tells Kara at the end of the episode that she had a sister who was killed by the Blight, hence her determination to destroy Pestilence.
- Locked Out of the Loop: The real mission of the Legion was to kill Pestilence, not stop her. Mon-El is obviously furious on how his teammates have kept him in the dark.
- Manly Tears: James gets quite teary while Winn is sick, musing about his life and being afraid of death.
- Marquee Alter Ego: Brainy’s image inducer gives him this
- The Needs of the Many: This is how Imra justifies killing Pestilence. One life today is millions saved in the future.
- Nice Job Breaking It, Hero: Imra's attempt to kill Pestilence end up triggering the resurgence of Purity, who comes to her sister's aid and cures her. Then they find Sam in Lena's lab.
- Not Brainwashed: In contrast to Sam/Reign and Julia/Purity, Grace is aware of what she does as Pestilence and likes it, as it gives her the power to take the lives of those she thinks deserve it.
- Pragmatic Hero:
- Imra is willing to kill Pestilence to save her future from the Blight.
- Despite seeing how painful and traumatic her procedure is on Sam, Lena nevertheless insists on continuing, as she fully believes it is the only way to save her friend.
- Pay Evil unto Evil: Pestilence targets the board of a health insurance company for denying care to those who need it.
- "The Reason You Suck" Speech: A downplayed and rather sympathetic one from Imra towards Kara, who desperately tries to describe the horrific effect the Blight had on her future, making countless innocent people suffer and how Kara's approach will do nothing to change that.
- Redemption Rejection: Grace plainly turns Supergirl's help down, because she loves being Pestilence.
- Red Herring: At first we're lead to believe that the girl who handed out cookies is Pestilence, but then she's found dead in her apartment, a victim of Pestilence.
- Revenge by Proxy: After Sam resists Reign's temptations one too many times, the latter threatens to brutally kill Ruby once she is free.
- Rousseau Was Right: Kara desperately wants to prove it with Pestilence. Imra doesn't want to give her the chance. Judging by Grace's comment that being a surgeon made her more cynical, Imra may be in the right here, at least with Grace/Pestilence.
- Shout-Out:
- When Brainy asks Winn who scratched him, the latter trolls him by describing Freddy Krueger.
- Supergirl compares J'onn to Yoda when he gives her an advice.
- Take That!: Mon-El and Brainy take a shot at Millennials, or rather the kind of Millennials who share their whole life on social media with random strangers, describing it as a mercifully short-lived fad. It doubles as Self-Deprecation as both actors are Millennials themselves (who, as celebrities, are on social media).
- Thou Shall Not Kill: Supergirl firmly states her adherence to this, and Mon-El says the Legion should, too, since their ideals were based on Supergirl. Brainiac 5 and Imra are willing to cross that line if it means stopping the Blight in the future.
- Token Trio: The three World Killers are played by actresses of Latina (Reign), African-American (Purity) and East Asian (Pestilence) descent.
- We Can Rule Together: In a sense. Reign gives Sam an offer to join her, framing it as an escape from her meaningless life. Sam doesn't bite, so Reign threatens her daughter, instead.
- Wonder Twin Powers: The World Killers enhance each other in close proximity. Purity saving Pestilence allows the latter to fight off the injection that would have killed her, and the two joining with Reign paralyzes the heroes on the spot, presumably an amped-up version of Purity's power.
