"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. However Mon-El reveals he appears in the 31st century.
  • 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 say '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. As he waves his hand, Obi-Wan says, "These aren't the droids you're looking for.
  • James hasn't worn or been being the Guardian around season 3, his alter ego finally returned.




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