Invasion! (The Flash) title card "Things were looking a little grim, but part of me was, admittedly, a little excited for a "reunion" of old friends."

Cisco Ramon[src]

This episode is part of a larger crossover series, Invasion!.

For the eponymous virus, see Medusa virus.
"In the event of an invasion, Medusa could be deployed to kill alien combatants while keeping our civilians and infrastructure safe from harm."
—The hologram of Zor-El to Kara on Project Cadmus' virus
"Medusa" is the eighth and midseason finale episode of the second season of Supergirl, and the twenty-eighth episode overall. It aired on November 28, 2016.

The episode starts the four-part crossover with the eighth episode of the third season of The Flash, eight episode of the fifth season of Arrow and seventh episode of the second season of DC's Legends of Tomorrow.


Eliza comes to town to celebrate Thanksgiving with her daughters. Alex decides it's time to come out to her mother, Kara is shocked when Eliza suggests Mon-El has feelings for her, and Winn and James consider telling Kara the truth about the Guardian. Meanwhile, Cadmus unleashes a virus that instantly kills any alien in the vicinity so Kara enlists an unexpected ally - Lena Luthor. The epic superhero crossover kicks off tonight when Barry Allen and Cisco Ramon seek Kara's help with an alien invasion on their Earth.[1]

Behind the scenes

  • The scene where Barry and Cisco arrive at Kara's loft is recycled in The Flash episode "Invasion!", the next part of the crossover.
  • This is the first episode of Supergirl that doesn't feature Kara's opening narration during the title sequence.
  • The Fortress of Solitude displays the same Kryptonian symbols seen in Smallville.


Promotional images


  1. Supergirl #2.8 “Medusa” Description: Helen Slater Returns - KryptonSite