Armek, a White Martian, descends on National City intent on taking M’gann back to Mars to face her punishment as a traitor. Hank and Supergirldetermine 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.
After Livewire seemingly breaks out of prison, Supergirl is intent on recapturing her. After training Mon-El, Supergirl takes him with her when she sees Livewire attack the NCPD but things go awry when Mon-El puts Supergirl before the citizens of National City. Meanwhile, James decides to come clean with Kara and M’Gann, has a psychic attack and collapses into a coma.