The episode will air on February 6 at 8 p.m. ET/PT on The CW.
In the episode, The DEO comes under siege from White Martians, who have come to take Miss Martian back to Mars to stand trial for abandoning her post and helping green Martians escape the camps.
Needless to say, this doesn't go over too well with Team Supergirl, especially Martian Manhunter, who hasn't got much use for White Martians.
WHITE MARTIANS ATTACK THE DEO — Armek (guest star Terrell Tilford), a White Martian, descends on National City intent on taking M'gann (guest star Sharon Leal) back to Mars to face her punishment as a traitor. Hank (David Harewood) and Supergirl (Melissa Benoist) determine the best way to keep M'gann safe is to bring her to the DEO. However, when it is revealed that Armek shape-shifted into M'gann and is now loose in the building, the team realize he could be disguised as any one of them.
David McWhirter directed the episode written by Gabriel Llanas and Anna Musky-Goldwyn.
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The midseason premiere of Supergirl — which is titled "Supergirl Lives" and directed by filmmaker Kevin Smith — will air Monday, January 23 at 8 p.m. ET/PT on The CW.