‘Supergirl’ continues to move at a breakneck speed. This week brings us the mid-season finale, which wraps up a number of ongoing storylines and ends with a flash from Supergirl’s past.
It’s Thanksgiving in National City. Kara has invited her mother, Eliza (Helen Slater), over for dinner, along with Alex, Jimmy and Winn. Alex and Jimmy fight over who gets to make a big announcement first. Alex wants to reveal her sexual orientation to everyone, while Jimmy wants to tell Kara that he’s actually Guardian. Before either can say anything, a rip in space/time (and, honestly, one of the show’s cheaper-looking visual effects) opens over the dinner table.
The next day at the DEO, Supergirl is determined to find out why Lillian Luthor would want a vial of her blood. J’onn, Alex and the others are convinced that Lena Luthor is in on the plot with her mother, so Kara goes to interview Lena in order to see if she can get any further information. Nothing comes of the chat, but Lena calls her mother immediately after Kara leaves.
Mon-El is enjoying a drink in the alien bar when he notices Hank Henshaw sneaking out of the place. Thinking it’s J’onn J’onzz, he follows him out to talk – and gets his ass whooped. Seconds later, a device that Hank/Cyborg Superman planted releases a toxic gas that kills all the aliens inside the bar. Mon-El is put under quarantine at the DEO until everyone can figure out if the gas will have any effect on him and whether he’s contagious. Alex enlists the aid of Eliza’s scientific skills to help.
Supergirl keeps Mon-El company by playing board games and flirting with him, when he suddenly starts choking and has to be taken to the infirmary. It looks like he was exposed to the gas, but it’s taking longer to affect him. Supergirl realizes that Lillian must have used her blood to gain access to the Fortress of Solitude, so she flies off there to see if she can figure out what happened. She’s almost immediately attacked by Kelex, the robot guard, who has been reprogrammed. She takes care of the robot relatively easily with her heat vision and then determines that the Project Medusa files were accessed. Supergirl talks to a holographic image of her Kryptonian father, Zor-El, and learns that Medusa is the poison gas Superman Cyborg released into the bar. It’s a bio-weapon created by Zor-El himself to protect Krypton from any other aliens… by killing anyone not Kryptonian (or human, apparently).
Back at the DEO, Alex is finally able to open up to her mother about her homosexuality – which, of course, mom doesn’t have a problem with at all. J’onn reveals to Supergirl that he’s slowly turning into a White Martian, but he insists on focusing on the problems at hand before any resources are used to cure him.
Eliza discovers that if the Medusa gas is combined with an isotope produced only by L Corp, it will create a chemical that can kill every alien in National City all at once. Supergirl flies off to confront Lena Luthor with the truth about her mother, but the youngest Luthor refuses to believe it. She accuses Supergirl of being a liar like her cousin and having a vendetta to destroy all the Luthors. After Supergirl leaves, Lena meets again with her mother, agrees to help her and offers her the isotope she needs.
Because Mon-El’s Daxamite physiology is close to that of a Kryptonian, the gas is taking longer to work on him. However, Eliza tells everyone that if they don’t find a cure soon, he’s sure to die as well. Waking up for a few minutes in the infirmary, Mon-El plants a kiss on Supergirl, indicating that there might be a future relationship for these two on the series. Winn then detects that the L Corp isotope is being transported toward National City’s port. The Luthors plan to launch a rocket over the city, which upon detonation will release the deadly Medusa gas over the entire population.
Knowing the danger to himself, J’onn insists on going with Supergirl to the port to stop the Luthors. When they get there, Cyborg Superman is on the scene. In a show of loyalty that Lillian insists upon, Lena launches the rocket. Supergirl flies off after it, leaving J’onn alone to fight Cyborg Superman. Initially, J’onn gets his butt kicked, until he goes full White Martian. Cyborg Superman craps his pants at the sight of the monster and J’onn stomps on him.
When Supergirl finally reaches the rocket, Lillian detonates it, releasing the toxin inside. However, it soon becomes obvious that the gas is inert. Lena has tricked her mother and never intended to help her. She also called the police in advance, who arrive on the scene to arrest Lillian.
Back at the DEO, Eliza has not only figured out how to cure Mon-El, but also how to restore J’onn’s blood cells to normal. Supergirl asks Mon-El about what happened between them, but he claims he doesn’t remember (or, actually, he does but isn’t saying), so Supergirl doesn’t bring up the fact that they kissed.
Speaking of kissing, Alex gets a visit that night from Maggie, who brings over pizza and plants one on her lips. I’m not sure how I feel about this. It seems to fall into that tired TV trope of having the only two (known) gay characters on the show hook up. Things were far more interesting when Maggie rejected Alex.
The episode concludes with Kara returning to her apartment to find that a familiar face has just jumped through another rip in space/time like the one that appeared at Thanksgiving. It’s Barry “The Flash” Allen and his pal, Cisco. They say that they need Supergirl’s help.
[Note: This story will continue on Tuesday night’s episode of ‘The Flash’, continue again on Wednesday’s ‘Arrow’, and conclude on Thursday’s ‘Legends of Tomorrow’.]