Plot
With the arrival of the third Worldkiller, Pestilence, Kara and Imra butt heads over how to go about dealing with the crisis. When Alex and Winn fall prey to the disease unleashed by Pestilence, the two heroines will put aside their differences to save the day. Meanwhile, Lena continues her analysis of Sam and tries to find a way to stop her transformations into Reign.
Influences
The Supergirl comics of The New 52 era (idea of World Killers)
Goofs
Wouldn't killing Pestilence before she becomes The Blight trigger a paradox, since she'd never exist in the future for The Legion to develop a cure for her?
Imra's previously reverential attitude towards Kara has been suddenly replaced with an attitude about her being "too naive", so as to force a conflict between them based on something beyond the Mon-El love triangle.
Ignoring Imra's issues with Kara, her failure to coordinate with the DEO seems out of character as well based on her past characterization.
We were told in previous episodes that the 31st Century has few historical records regarding the 21st century. How then can Imra be so sure that Kara's plan to stop The Worldkillers by appealing to their human halves will fail when she doesn't know what Kara's original plans were or what her presence is doing to alter the past? It could be that The Worldkiller's presence wasn't originally known until it was too late for Supergirl to do something!
You'd really think Brainiac-5 would know enough about basic medicine to know how vaccines work and how The Blight cure probably wouldn't work on the earlier plague Pestilence generates.
Even if they don't think Pestilence's virus is airborne, shouldn't everyone in the DEO lab be wearing scrubs and masks? Even if the non-humans can't be infected, they could still be acting as carriers.
Shouldn't they also be keeping James Olsen out of the lab where the sick, possibly contagiousm people are?
Performances
Mehcad Brooks hasn't always had a lot to do on this show, but the middle section where he lends a dying Winn an ear and then talks to Lena about her secret work offers a welcome bit of honest humanity in an episode that's a bit too heavy on forced melodrama.
Super Trivia
Pestilence strongly resembles a Worldkiller from the original New 52 Supergirl comics called Perrilius. Perrilus had the power to generate toxins and poisons, killing those around her.
Technobabble
The Blight is preceded by mass wildlife death and plant life, crops rotting in the ground itself.
It has a short incubation period and is 100% fatal and extremely contagious.
The dead birds Alex examines show no signs of having any disease, yet they all underwent catastrophic organ failure.
Imra's plan is to weaponize the cure for The Blight in her DNA and use that to kill Pestilence before she becomes a major threat.
Brainiac-5 has a personal image inducer which he uses to make himself look human.
The symptoms of The Blight include high fevers and bloody noses.
The genome of Sam's DNA is rewritten whenever Reign is triggered. Lena theorizes that there is a special enzyme that triggers this change and that it can be isolated and eliminated.
Sam's transformation into Reign seems to be brought about by a pain response, Lena triggers the transformation with 500 volts of electrical current.
All of the victims of Pestilence show signs of having been scratched. This backs Alex's theory that The Blight is passed through blood - not through the air or person-to-person contact.
The dark valley of Sam's dreams is a parallel dimension her mind goes to when Reign takes over her body. With Lena repressing Sam's ability to transform physically, it stopped Reign's ability to manifest fully in the real world. This enabled Sam and Reign to speak to one another and for Reign to deliver a warning that someone was coming for both of them.
Alex's analysis of Winn suggests that the scratches don't manifest until the rest of the symptoms do and the only trace evidence she could find was a mild anesthetic.
Brainiac-5 claims that the odds of stopping The Blight from existing by killing Pestilence are 98.459% The odds of stopping Pestilence by appealing to her humanity are 52.744%.
The Blight vaccine doesn't work on the Pestilence plague because it is not technically the same virus but the ancestor of it. This means they need a sample of Pestilence's DNA to adapt the cure to save Winn.
When Supergirl last fought Purity, Winn was able to identify the frequency of Purity's sonic scream. This enabled him and Braniac-5 to program the DEO satellites to scan for that frequency and alert them once it was detected.
Dialogue Triumphs
Alex: We have a lead on a treatment.
Doctor Grace Parker: You do? Already?!
Winn: Well, we work really fast on account of being really smart. (laughs)
Doctor Grace Parker: Some people find humor charming during stressful circumstances.. I find it's a mask for a lack of confidence.
Winn: (forced chuckle) Well, I find that... I have no retort.
Brainiac-5: Winn. You're a slightly smarter than average human. Tell us you remember who scratched you.
Winn: (mock gasp) Oh! There was a guy with the gloves! And the knives! And the burnt face!
Brainiac-5: Go on! (To Kara and Alex) This sounds like a very promising lead. (To Winn) What else do you remember?
(Kara is biting her lip. Alex looks annoyed as Winn continues to ham it up.)
Winn: Oh, so scary, man! I couldn't even look at it!
Alex: It's Freddy Kruger!
Brainiac-5: You know him too? Eureka!
Kara: It's a character in a movie.
(Winn laughs.)
Brainiac-5: Facetiousness. My greatest weakness.
Kara: Do you think I'll get through to Pestilence?
J'onn: There's no way of knowing. You just have to try.
Kara: That's not what Yoda would say.
J'onn: (scoffs) Oh, yeah. Yoda. "Do or do not." He was wrong about that one.
(Kara chuckles lightly.)
J'onn: You know, these days... I don't know what my father will remember. I wake up and have the same conversation with him every day. I keep at it because sometimes he remembers that we've had that conversation before, and we actually laugh about it. I keep trying. I keep talking. So that he can find those moments of clarity. And laugh. Just because something is hard, doesn't mean it's impossible. You break through impossible every day. You inspire the rest of us to do the same.
Kara: You're a good son. And thank you.
Brainiac-5: Are you two having a marital conflict which I should stay out of, or is this a work-related quandary where my intellect might be of use?
Mon-El: Some decisions can't be made with a math equation.
Dialogue Disasters
Imra: Whatever you do in this time to try and stop her fails. You fail. So if I get the chance, I will end this.
Pestilence: They say that surgeons have a God complex, but it's simple. I am a god!
Continuity
The early evidence suggests Pestilence to be a woman named Adelaide "Addy" Swanson who works in the National City Mayor's Office. She is famous for her lemon poppy-seed cookies. She is later found dead of the plague by Supergirl.
Kara refers to the confrontation with Purity in 313 and how that went badly because they were too aggressive.
Winn somehow recognizes who Brainiac-5 is when his image inducer is active.
The mayor, chief of police and five city councilman of National City are among the first human victims of Pestilence.
Sam tells Lena about her reoccurring dreams of a dark valley. She says that this time she saw it was a real place and Reign was there. Lena says this dark valley is a parallel dimension where Sam's mind goes when Reign takes over her body.
Imra says she has no reason to listen to anything Supergirl wants to do because clearly whatever she wanted to attempt in the past to stop The Worldkillers failed.
Mon-El says that Imra sent The Legion on this mission for reasons of vengeance, but does not specify what that means. He does reveal that Imra is hiding her real reasons for wanting to kill Pestilence from Kara.
Winn talks about making peace with his mother in 314.
Social media does not exist in the 31st century. Brainiac-5 finds the concept "delusional".
Pestilence is revealed as Dr. Grace Parker - first in her class at Metropolis School of Medicine, now an emergency surgeon at National City General Hospital.
As of this episode, Pestilence only has the power to retract her fingernails and creates some kind of venom. Her touch can also cause plant-life to wither and die. She appears to have some degree of enhanced durability as well. At the end of the episode, she is revealed to have super speed.
Purity is somehow able to negate whatever Imra injected Purity with to kill her. Still, the needle gives them the DNA sample they need to create a cure for Pestilence's plague.
Imra had a sister named Preya, who died of The Blight. She was quiet and stuck to herself. This is why Imra was so determined to kill Pestilence.
Together, all three World Killers can unleash a psychic attack that renders great pain in the people around them along with a blinding light.
Reign is also revealed to have the power to will a costume to will around her.
Untelevised Adventures
Brainiac-5 apparently nearly caused a riot when he went out in his normal form and attempted to buy apple cider vinegar from a Piggly Wiggly.
The Fridge Factor
It seems like most of Imra's real issues with Kara are sub-textually about her worrying about Mon-El wanting to be with Kara rather than Pestilence.
The Kryptonite Factor
Honestly, most of the problems in this episode would have ended in about five minutes of Imra would just be honest with Kara.
The Bottom Line
Largely bland filler up until the last two minutes. As has been typical this season, the best moments of the episode were those dealing with the character interactions and the personal subplots rather than everything to do with The Worldkillers. The Worldkillers really aren't that interesting as a concept (there's a reason why they were never used again after their initial appearance in the second Supergirl arc in the New 52 era) and there's nothing here to make us care about Dr. Grace as an individual like there was in the episode with Purity. Throw in the nonsense with Imra fighting with Kara just to add drama for the sake of drama and you have one flat, but not painfully awful, episode.