"This world is a crazy place right now. People acting, reacting. Escalating behaviors. Like what Morgan Edge did to Lena. What our lawmakers are doing. Sniping at each other, going round and round in circles, not doing any good. Reminds me of Mars before the civil war. But like my father said then, 'There is great power in being the calm in the center of the storm. A beacon, to show the way.' Supergirl is here to remind us on Earth about what's best in ourselves. That's what's most important. It's more important than if you were to ever catch another bullet."
J'onn J'onzz to Kara
"For Good" is the twelfth episode of the third season of Supergirl, and the fifty-fourth episode overall. It aired on January 29, 2018.


Someone tries to kill Morgan Edge and he barely survives. He accuses Lena of being behind the attempt and vows to destroy her. When Lena fears her hatred for Morgan will take her to the Luthor dark side, Kara steps in to help her friend. Meanwhile, after Sam realizes she's losing time, she confides in Alex who decides to run some medical tests to see if she can find out what's going on with her new friend.[1]


  • Winn reveals Superman has already killed Zod. This is a reference to The 2013 film Man of Steel.
    • However, Mon-El revealed Zod will return in the future.
  • Alex's mention of working as a doctor in Seattle before joining the FBI is likely a nod to Chyler Leigh's role as Lexie Grey in Grey's Anatomy and Private Practice.
  • Mon-El mentions getting the idea to use Lillian's drone against her from a battle alongside Brainy with Computo. In the comics, Computo was created by Brainiac 5.
  • Winn says "Sorry, these are not the drones you're looking for." In Star Wars Episode IV: A New Hope, Obi-Wan Kenobi uses the Force to convince two Stormtroopers to overlook R2D2 and C-3PO by waving his hand and saying, "These aren't the droids you're looking for."




  1. Supergirl - Episode 3.12 - For Good - Press Release - SpoilerTV