Supergirl: Season 4, Episode 21

4 - 21: Red Dawn

Kara comes face to face with Red Daughter and the two engage in an epic battle. Determined to find a way to extract the Harun-El, Lena turns to an unlikely source for help – Lillian Luthor. Meanwhile, Alex realizes she’s missing parts of her memory, and Brainy, Nia and J'onn set out to track down aliens who have been abducted by Lex.