Take a look @ footage, images and synopsis from the new "Supergirl" episode "The Martian Chronicles", written by Gabriel Llanas, Anna Musky-Goldwyn and directed by David McWhirter, airing February 6, 2017 on The CW:
"...'Armek' (Terrell Tilford), a 'White Martian', descends on 'National City' intent on taking 'M’gann' (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..."
Click the images to enlarge and Sneak Peek "Supergirl: The Martian Chronicles"...