Supergirl Recap with Spoilers - The Martian Chronicles

The episode opens with Kara walking into the alien bar to talk to Mon-El. She explains to Mon-El that she doesn't think they're a great match, in part because she's busy juggling superheroics and her career. She also awkwardly states that she wouldn't date "someone like him". That causes Mon-El to walk away, right as Alex approaches her. Alex also drops some bad news on Kara: Maggie wants to take Alex to her first concert as a couple instead of attending Kara's Earth Birthday. Kara tells Alex to go, but she requests that M'gann bring her whatever Mon-El is drinking. However, M'gann tells Kara that Mon-El has only been drinking club soda (Kara's drink of choice) as of late.

When M'gann goes outside, she finds out J'onn spying on her. J'onn wants to protect M'gann from the approaching White Martians, but M'gann says they aren't on Earth yet. That, of course, means that a White Martian immediately shows up to attack the pair. While the White Martian overwhelms both M'gann and J'onn, he flees when Supergirl flies out to help.

Back at the DEO, Supergirl briefly lectures Winn about Guardian (bringing up the fact that he got beat up several weeks ago), before M'gann says that she doesn't want to stay at the DEO for protection.

When M'gann goes back to the bar, her WHITE MARTIAN HUSBAND Armek shows up to bring her back to Mars. He threatens both Supergirl and J'onn and says she has two hours to turn herself in.

Later that night, M'gann tries to leave National City, but J'onn stops her. J'onn convinces her to come back to the DEO for her own protection.

Maggie tries to get Alex excited for their Barenaked Ladies concert, but Alex is worried she hurt Kara's feelings. Maggie goes to the DEO to check on Supergirl, but Supergirl claims that she's okay. J'onn arrives with M'gann to help track the White Martians down, but when another M'gann shows up, J'onn realizes he's been had. J'onn tries to apprehend the fake, but the White Martian gets the upper hand and shuts down the power. By the time Winn gets the power back on, the White Martian is gone. J'onn puts the DEO on lockdown to stop Armek from escaping, but Winn correctly points out that it could be hiding as one of them.

Winn suggests they just use personal questions to suss out Armek, but J'onn points out that the White Martian can read minds. What's more, J'onn can't read anyone's minds due to some kind of psychic interference. When everyone gets twitchy, J'onn says there's another way to detect a White Martian: fire.

J'onn lights up a bunsen burner in the lab, and everyone puts their hand to the fire...even J'onn. Winn tries to stall and when he puts his hand to the fire, his hand turns into a White Martian. Winn/Armek uses the burner to blow everyone back and tries to kill J'onn, but Supergirl uses her super breath and heat vision to scare him off.

Supergirl and the rest of the agents recover from the attack, when an alarm goes off because Armek has rigged the building's reactor to explode, which will kill everyone within a 10 block radius. In order to stop the reactor, J'onn says they need to find the real Winn to override the system.

Alex and Supergirl search the building and have a heart to heart about Kara's "Earth Birthday". Supergirl admits that she was mad earlier, but only because she's afraid of change and doesn't want to be abandoned by Alex.

J'onn pairs up with M'gann and admits that he's in love with M'gann. They find some White Martian slime and discover that both Winn AND Alex have been captured by the White Martians. J'onn warns Supergirl, but the second White Martian morphs and attacks Supergirl. While Supergirl fights the White Martian in the reactor room, J'onn wakes Winn and Alex up. Winn says he needs to get to the reactor to shut it down. When he arrives, Armek tackles J'onn while Winn scrambles to shut down the reactor. Armek gets the upper hand on J'onn but M'gann arrives to help even the odds.

Supergirl takes out her Martian, while M'gann impales Armek with a pipe. Winn shuts down the reactor with 12 seconds to spare. When Armek suddenly gets up, Alex walks in and shoots him in the chest with her new gun.

With the DEO now out of lockdown, Alex rushes off to call Maggie about their concert and Winn leaves to help out James, leaving Supergirl with no one to celebrate her Earth Birthday with.

M'gann tells J'onn she needs to go back to Mars, to help inspire other White Martians to not be evil. She says that J'onn inspired her to stand up and fight, but J'onn isn't thrilled that she's leaving.

Alex surprises Kara at her apartment with a cupcake. Alex says she vaguely remembers Kara's conversation with the White Martian (because of the psychic bond) but she promises that she's not going to abandon Kara. Alex then suggests that she was overcompensating with her Earth Birthday because she's confused about how she feels about Mon-El. Kara admits that whenever she puts herself out there, it backfires. Alex suggests that she give it a shot anyways.

Before M'gann leaves, she tells J'onn that she loves him too. M'gann then "transmets" away to her White Martian ship.

The next morning, Kara runs into Mon-El at work as he heads to lunch with Cat/James's assistant. Kara almost tells Mon-El how she feels, but she decides to walk away instead.