While the lion’s share of the advertising and general hype surrounding this episode of Supergirl is about its impending crossover with the other CW superhero shows, writer Jessica Queller and Derek Simon don’t abandon the show’s arcs and relationships for guest stars and dimensional rifts. “Medusa” is centered around relationships between mothers and daughters and family in general as Lillian Luthor tries to get Lena to join the family business and release a bio-weapon killing. On the more heroic side of things, Supergirl works with her adoptive mother, Eliza Danvers (a very pleasant Helen Slater). The intertwining of the family secrets and the passive aggressive sniping of the Luthors thanks to Brenda Strong along with the added side dish of Martian Manhunter struggling with becoming a White Martian elevates the plot, which is a standard quarantine disaster movie or the X-Men “Legacy Virus” crossover without them.

The theme of family is definitely fitting for an episode immediately airing after Thanksgiving, and director Stefan Pleszysnki uses warm lighting and plenty of shots of Kara and her friends and family to show their bond despite “secrets,” like James Olsen being the vigilante Guardian, or more seriously, Alex Danvers coming out as lesbian to her mother. Alex does come out to Eliza later in the episode in a warm moment of acceptance, but thankfully the Guardian subplot is sidelined for this one. Helen Slater is basically a human sunbeam, and even though she mainly plays the role of scientific exposition or fixer of bio weapons, she brings intelligence and love to each scene. This is a total contrast to Kara’s real father, Zor-El, who is responsible for creating the basically racist bio weapon Medusa, which can destroy the DNA of any non-Kryptonians as a last ditch weapon.

It’s disconcerting that Kara’s father, who instilled in her the values of goodness, hope, and being “stronger together”, created something that could be used for genocide and could kill innocents. Melissa Benoist’s performance as Supergirl is less bright and more pensive than usual after this reveal as she talks to Martian Manhunter about her father’s terrible legacy. As the lone survivor of a world he would have given anything to save, he slightly understands Zor-El’s motivation, but mentions this in passing and instead comforts Kara. David Harewood channels the noble, honorable warrior inside of J’onn Jonzz that comics fans and viewers of the Justice League cartoons have loved for years as he flies out to help stop Lillian Luthor from releasing the bio weapon. He has a passion for good that can’t be drowned out by the White Martian DNA devouring his body even if this disease makes for some nifty special effects makeup.

In “Medusa”, we finally get to see Lena and Lillian Luthor share some extended screen time, and Queller and Simon make their pacing around an office scenes more tense than Cyborg Superman getting his block knocked off or doing a “super punch” for the umpteenth time. (There is nothing wrong with punching just a character that exists as a one-dimensional goon, punching bang, and waste of David Harewood’s acting talent.) Brenda Strong continues to be the queen of passive aggressive condescension mixed with the cold, hard truth. (Yes, she prefers Lex to Lena.) Katie McGrath pulls out all the acting stops going from being the easygoing friend as Kara “interviews” her to get information about Cadmus and her mother to the cold, disdainful daughter measuring each syllable in venom when her mom decides to drop in. And she is especially entertaining in villain mode with raised eyebrows and a purr that evokes Eva Green if she ever decided to play Lady Macbeth. And Pleszynski holds the reveal that she sabotaged the bio-weapon for quite a while hinting at some dark irony as aliens celebrate red sparks that fall from the sky and do nothing.

And this being a CW show, this review wouldn’t be complete with an overindulgent discussion of the romantic pairings in “Medusa”. Queller and Simon go to the soap opera well and have Kara and Mon-El share a kiss while he is on his “death bed” after being exposed to the bio weapon. It isn’t really logical that Kara would fall for a kind of sexist, kind of adorkable, and slightly cowardly guy like Mon-El, and the “bonding” scenes where they play Monopoly and discuss the meanings of “crush” and “like” don’t really help. He is attractive, but it seems like the Supergirl are trying to do Romeo and Juliet with DC Comics aliens and hopefully less bloodshed in their relationship. It lacks the spark of, say, Alex and Maggie or even Oliver Queen and Felicity Smoak in early seasons of Arrow. Plain and simple, Mon-El is way too douchey to be with Kara.

But, on a happier note, Maggie Sawyer and Alex share a beautiful scene at the end of “Medusa” , which acts as a rousing conclusion to Alex’s coming out arc. It’s kind of cute, kind of awkward, and also very empowering as Maggie finally realizes that Alex came out not so she could be with her, but that she could finally completely be herself. There’s great symmetry between both her chat with her mother and Maggie about finally being able to feel her full identity, but substitute familial for romantic love. Maggie and Alex finally share a long kiss, but it’s the little pause where Alex asks Maggie if she likes her that encapsulates their relationship as Alex is still a little unsure of herself after Maggie previously rejected her. This hesitancy and fear makes Alex’s coming out that much more organic because even if your friends and relatives aren’t homophobic, the process can be a little awkward. Luckily, Alex has a supportive mother and sister.

As Supergirl Radio podcast host Carly Lane astutely tweeted, “Medusa” is like a zero issue or prologue for the “Heroes vs. Aliens” crossover with The Flash and Vibe enlisting the help of their extraterrestrial ally in a battle against a mysterious alien threat. There is a scene with aliens on a ship that seems spliced in from a later episode or another show altogether, but mostly the “crossover” scene at the end is a reminder of Gustin and Melissa Benoist’s adorable chemistry (They give the best hugs. with a tinge of sadness as Barry and Cisco aren’t on the best of terms. And in true comic book fashion, the episodes ends on an energetic cliffhanger as Kara will get to meet Team Flash (and possibly more people) tomorrow night.

With the reveal of Zor-El as potential destroyer of worlds, Jessica Queller and Derek Simon find a real commonality between Lena and Supergirl in “Medusa”. They are both daughters trying to make something better out of their family’s misdeeds even if Luthor will always have a more villainous ring to it than El unless you’re a disgruntled train commuter. This through line of family, especially mothers and daughters, keeps this Supergirl focused, but some fun romantic, Martian, and speedster detour don’t derail it.

Overall Rating: 8.0