Last week on Supergirl, Lena Luthor revealed that she has been examining Sam and reveals the truth to her CFO, that she was Reign the World Killer. Sam doesn’t realize it as she blacks out when she goes on her murderous sprees. Only when she shows Samantha video of her as Reign does she start to connect the dots. Even though Lena promises her that she will help Sam her overcome her evil alter ego, Lena’s got her work cut out. Mon-El tries to train Kara on using her uniform as a weapon, but thanks to M'yrnn having a psychic breakdown, the negative energy affected Kara (as well as the rest of the DEO). Mon-El did tell Kara about the Legion’s true mission, to stop one of the World Killers name Pestilence, who is responsible for the death of countless people in the future.
This week, we get to see Pestilence in action.
Last week ended with countless dead birds and served as a canary in the coal mine for this week’s episode. The Legion and the DEO realize that this third World Killer will be a big problem if her powers continue to manifest and grow. Irma wants to kill her once they discover who she is. Kara, always about “truth, justice, and the American way” doesn’t want that to happen. She feels that if they reach Pestilence’s human counterpart, they can talk her off the ledge and stop her before she starts. However, it’s already starting as countless people in National City are starting to become sick.
At a quarantine zone, the team discovers that the people who became sick got sick as the result of a scratch. However, Pestilence could be anyone. Irma wants to set up a force field and trap everyone within the quarantine zone, but this proves to cause more of a panic than the outbreak. This is the first time that she and Kara but heads in this episode. This causes a rift amongst the Legion as well. Brainiac (who is using an image inducer to look normal) theorizes that if they kill Pestilence, there’s a 98% certainty that they will avoid the plague in the future. If they don’t and just use their super DNA to make an antidote, it’s still only a 50% chance of success. To make matters worse, Winn in starting to show sickness as well, meaning that he was scratched by the mysterious culprit. After Winn gets suck, so does Alex.
Meanwhile, Lena is continuing her analysis of Samantha to learn more about Reign and how to stop her. This forces her to torture her friend, which sends her to another dimension where she actually runs into Reign. Reign tries to psychoanalyze Samantha saying that letting go is the best option as he life didn’t have much meaning anyway. Being Reign would be the best thing that she can do. This makes Samantha hesitant to continue the experiments. But at Lena’s insistence, she continues to work with her.
That’s when the Deo discovers that Pestilence is none other than the doctor who was supposedly trying to stop the outbreak. Kara tries to appeal to doctor Grace, but even her human side is on board with becoming a World Killer. While they stop her from poisoning a group of insurance executives (who Grace says deserve to get deathly sick), Kara gets scratched and starts to get sick as well. Lucky for the group, they were able to obtain some of Grace’s DNA in the scuffle, enough to make an antidote. At the last minute, Purity comes and rescues Pestilence.
Just then, the sensors go off at the DEO as they now know where the two World Killers are heading to next. Kara, Mon-El, Irma, and J'onn arrive at Lena Luthor’s lab where they discover what she’s been doing to Samantha. Just as they arrive, so do the other World Killers who then proceed to beat all of them and rescue Samantha, revealing to Kara that he good friend is in fact, her mortal enemy.
Next week, all three World Killers are together. That can’t be good!
