The Martian drama that's been simmering on "Supergirl" ever since M'gann was introduced earlier this season is about to reach a boil. Following last night's episode of the CW superhero drama, a new promo for next week's episode -- titled "Martian Chronicles" -- was released.

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The new promo focuses on the tension between Martian Manhunter (David Harewood) and M'gann (Sharon Leal) following the arrival of a White Martian. But things go from tense to super-tense when the shape-shifting White Martian breaks loose in the DEO, thus causing the "Supergirl" cast to wonder who among them is really who they seem to be.

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 & Anna Musky-Goldwyn (#211). Original airdate 2/6/2017.

Starring Melissa Benoist as the Girl of Steel, "Supergirl" airs Mondays at 8 pm ET/PT on The CW. The series also stars David Harewood as Martian Manhunter, Mehcad Brooks as Jimmy Olsen, Chyler Leigh as Alex Danvers and Jeremy Jordan as Winn Schott and features appearances by Calista Flockhart's Cat Grant as well as Tyler Hoechlin's Superman.