The DEO manages to track down one of the Worldkillers — Purity. Meanwhile, Sam takes some needed time off from L-Corp, but her break doesn't turn out how she hoped.
Tropes:
- Arranged Marriage: Mon-El reveals that this is how Imra and he came together. Over time, it evolved into a Perfectly Arranged Marriage (or so he believes), but after being reunited with Kara, he has very conflicting feelings.
- Badass Boast: Courtesy of Purity:"I am the scalding light. I am the flood that sweeps away sins. I am the word and cry of justice."
- Big "SHUT UP!": When Sam learns that Lena told Ruby that she is sick, she gets mad and eventually tells her "Silence!" as Reign before regaining her senses.
- Cliffhanger:
- The episode ends with Lena finding out that Sam is Reign. Considering the two-month hiatus between this episode and the next, that's quite a note to leave it on.
- Shortly before that, Imra reveals to Mon-El that the Legion has a secret mission he was kept in the dark about and implies that she has been deliberately repressing his feelings for Kara.
- Drunk on the Dark Side: Compared to Reign, who only shows grim determination, Purity is clearly having a blast while using her powers.
- Failed a Spot Check: Apparently not one person in a crowded ice rink sees Sam take off flying.
- Forced to Watch: Unlike Sam, who isn't aware of what she does as Reign, Julia is able to perceive what she does as Purity, if only when Purity lets her. This ends up biting her, as doing so allows Alex to reach Julia and convince her to take control from Purity.
- Good Cop/Bad Cop: Kara tries to appeal to Purity, while Alex (at first) constantly threatens her.
- Hannibal Lecture: When Alex tries to intimidate Purity, she quickly turns the tables on her, correctly deducing that Alex only acts this way because of her inner anger and fear, causing her to storm out of the room and break down in Winn's arms.
- Headphones Equal Isolation: Julia is so into her music that she does not notice a SWAT team breaking into and searching her house!
- Heroic Sacrifice: Julia gives herself to Reign to stop her from killing Alex.
- "I Know You're in There Somewhere" Fight: Attempted over the course of the episode with Purity in an attempt to draw Julia out. It finally works near the end, but then Reign shows up and Julia turns herself over to spare Alex.
- Internal Reveal:
- The DEO finds out that the World Killers have split personalities.
- Lena finds out how long Sam's been having black-outs and disappearing, and later learns that Sam is Reign.
- Jerk Justifications: Alex breaks down at the end of the episode, citing her pain and loss after the breakup with Maggie she relives everyday for her aggressive behaviour.
- Keeping Secrets Sucks: Imra and Mon-El are having a hard time due to Mon-El not talking to Imra about his lingering feelings for Kara.
- Load-Bearing Hero: Purity breaks a subway's support beam, forcing Mon-El and J'onn to hold it up. J'onn tells Mon-El he can hold it by himself, allowing Mon-El to join the battle.
- Locked Out of the Loop: Imra has been keeping the true purpose of the Legion's mission from Mon-El. Whatever it is, he probably won't be happy.
- Make Me Wanna Shout: Purity's power allows her to control vibrations, either over a wide area or concentrated into a powerful scream.
- Nice Job Breaking It, Hero: Alex's overly-aggressive behavior towards Julia when they first show up at her house wakes up Purity, and it takes the rest of the episode for them to get through to Julia once more.
- Nice Job Fixing It, Villain: As she's choking out Supergirl, Purity admits that Julia can see and hear everything that's going on. That is promptly used against Purity to break her control and put Julia back in charge.
- Oh, Crap!: Purity has a big one when her powers don't work on the heroes due to Winn's countermeasure.
- Plug 'n' Play Technology: Averted here. Despite the Legion ship and J'onn's shapeshifting car running on similar power sources, simply wiring them together fails because the Martian battery is calibrated differently than the Legion battery.
- Pop-Cultural Osmosis Failure: J'onn can hear loud headphones during the house raid and muses, "Is that Lisa Loeb?" A puzzled Mon-El replies, "I thought the target's name was Julia Freeman."
- Rabid Cop: Alex is extremely on the edge for most of the episode, outright threatening Purity that she is about to be vivisected!
- Rousseau Was Right: Kara is adamant that she can talk Purity into letting Julia out. She's right.
- Self-Deprecation: Mon-El comments on how much of a sexist he used to be and how it led to him and Kara butting heads.
- Smug Snake: Purity outdoes Reign in sheer arrogance and self-righteous gloating, to the point of pretending Julia was just a part she was playing all her life, only to reveal when she has Kara in a headlock that Julia is very much real and being forced to watch her cruel actions.
- Superpowered Evil Side: Just like Reign is this to Sam, Julia has absolutely no control over Purity's actions.
- Swapped Roles: First, Alex is very adamant on not giving Julia any benefit of the doubt while Kara tries appealing to her. After her escape, Kara becomes briefly just as determined to take her down, while Alex actually succeeds in talking Julia down from killing Kara.
- Sympathy for the Devil: Both Kara and Alex (in the end) feel very sorry for Julia and Kara even plans on not killing, but saving, the World Killers.
- Try to Fit That on a Business Card: Alex mocks Purity's introductory Badass Boast by saying that it's too long and asking if there's a condensed version they can use.
- The Unreveal: Apparently, there was a specific reason the Legion came to the past that Imra didn't tell Mon-El, leaving him to believe it was an accident. The scene cuts away before she can tell him (and the audience).
- Wrestler in All of Us: Purity uses a headlock backbreaker on Kara.
- You Are Better Than You Think You Are: Alex talks Purity down from killing Kara, appealing to her good side, Julia.
