Some days on Supergirl there is A LOT of talking going on. And the beginning of this episode, you’d have thought this going to be one of them. Kara and Mon-El at the bar, trying to come to terms with him telling her his feelings at the end of last week’s episode. Kara and her sister, missing out on Kara’s “Earth Birthday” plans so Alex can go to see Barenaked Ladies with Maggie Sawyer. J’onn and M’gann talking in the alley after he’d spent the day following her around, making sure she was still safe.
From what you might ask? It was revealed last week that the White Martians, the evil race that killed J’onn’s family and the rest of the Green Martians before J’onn came to Earth, knew where M’gann was and were coming for her. And sure enough, the two are attacked by a rampaging White Martian who has the upper hand on them both until Kara arrives and fights him off.
Armek, the White Martian, returns to the bar later in human form, where he confronts M’gann, his former wife, and threatens to finish her and her new “human” associates if she doesn’t return with him. She thinks about running but is convinced not to by J’onn who tells her he and their friends will take care of her. The last bit of cute goes out the window when Alex comes back to work to check on Kara and M’gann shows up to talk to J’onn. And then M’gann shows up to talk to J’onn. SHAPESHIFTERS!!! First M’gann is Armek and he and J’onn go hand-to-hand, before Armek turns invisible and disappears. J’onn locks down HQ before he can get away, leaving everyone wondering who’s really who they claim.
Paranoia runs rampant as DEO agents accuse each other of being Martians, guns are drawn and friends are close to enemies when J’onn and M’gann suggest a Martian fire trial which will reveal everyone’s true identities. Agent Vasquez and the other agent pass. J’onn and M’gann also pass. Wynn is next and he’s revealed to be the traitor and disappears again, this time with another plan. He sabotages the DEO building’s reactor and primes it to explode. The team’s new mission is to find Wynn to fix the reactor AND stop Armek from killing everyone. Kara and Alex search together and their heart-to-heart are interrupted when the other search team finds…ALEX!
Armek brought a partner who replaced her and she and Kara duke it out while J’onn and M’gann find Wynn and get him started on the saving the building. The fights end as you’d expect, Supergirl defeats her sister’s doppelganger while J’onn and M’gann defeat Armek. M’gann saves J’onn from the rampaging White Martian by impaling his skull with a metal rod. Alex's doppelganger regains consciousness and she gets to blast her with her newly found ray gun.
Too little too late for our heroes unfortunately. Kara talks to Alex who convinces her that she’s been hiding her feelings for Mon-El , but when she goes to see him, he’s already heading to lunch with Miss Tessmacher, having moved himself to Kara’s friend zone (we think). J’onn and M’gann, having just revealed their feelings for one another, go their separate ways, with M’gann going back to Mars in an attempt to find other like-minded White Martians to try and free Mars from White Martian rule. Oh the life of a hero. Better luck next time!