Kara and Lena head to Stryker's Island to search for clues on how to defeat Lex. At the prison, Kara tries to befriend a nosy prisoner, Steve, who may have insight into what Lex was doing, while Lena studies an array of puzzles Lex left behind in the hopes of discovering his whereabouts. While there, a prison riot breaks out and Kara must find a way to stop the prisoners without revealing her secret identity as Supergirl. Meanwhile, Kelly encourages James to talk to someone for his PTSD.
Season 4 Episode 18 of Supergirl was watched by 990,000 viewers, resulting in a 0.30 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.