Supergirl's powers are tested when Reactron, one of Superman's formidable enemies, arrives in National City and targets the young hero. Also, Cat plans to run an exposé on Supergirl.
Season 1 Episode 3 of Supergirl was watched by 8,070,000 viewers, resulting in a 1.70 rating in the 18-49 demographic.
After 12 years of keeping her powers a secret on Earth, Kara Zor-El decides to finally embrace her superhuman abilities and be the hero she was always meant to be.
Twelve-year-old Kara escaped the doomed planet Krypton with her parents' help at the same time as the infant Kal-El. Protected and raised on Earth by her foster family, the Danvers, Kara grew up in the shadow of her foster sister, Alex, and learned to conceal the phenomenal powers she shares with her famous cousin in order to keep her identity a secret.
Years later at 24, Kara lives in National City assisting media mogul and fierce taskmaster Cat Grant, who just hired the Daily Planet's former photographer, James Olsen, as her new art director. However, Kara's days of keeping her talents a secret are over when Hank Henshaw, head of a super-secret agency where her sister also works, enlists her to help them protect the citizens of National City from sinister threats. Though Kara will need to find a way to manage her new-found empowerment with her very human relationships, her heart soars as she takes to the skies as Supergirl to fight crime.