Supergirl acts like a jerk after being exposed to some Red Kryptonite, and National City may pay the price.
As DC Comics fans know, Red Kryptonite is famous for causing dramatic shifts in the personalities of Kryptonians. According to the episode's official synopsis, for Kara, it will turn her from the cheery superhero we know to "malicious and dangerous" -- for one week, at least.
"Falling" -- Kara (Melissa Benoist) turns on her friends and the citizens of National City after being exposed to Red Kryptonite makes her malicious and dangerous.
"Supergirl" airs 8 p.m. Mondays on CBS.