In the season premiere episode, “American Alien,” diving back into reporting, Kara (Melissa Benoist) welcomes a new cub reporter to CatCo. Meanwhile, James (Mehcad Brooks) and Lena (Katie McGrath) argue about James' impending indictment for acting as the vigilante Guardian, while Alex (Chyler Leigh) and Brainy (Jesse Rath) struggle to get in sync at the DEO. Supergirl (Melissa Benoist) is called into action when remnants of the anti-alien terrorist organization Cadmus try to assassinate pro-alien leaders, but their endgame turns out to be much more sinister than she expected. J'onn (David Harewood) relishes his peaceful new life, but an outing with an old friend causes him concern.
Based on the DC character, Supergirl AKA Kara Zor-El, decided to embrace her superhuman abilities and become the hero she was always meant to be. When she was 12 years old, Kara Zor-El escaped the doomed planet Krypton and was sent to Earth where she was protected and raised by her foster parents, Jeremiah and Eliza Danvers and her foster sister, Alex. Under their supervision, Kara learned to conceal the phenomenal powers she shares with her famous cousin, Superman, in order to keep her identity a secret.
Years later, Kara was living a “normal” life in National City, assisting media mogul and fierce taskmaster Cat Grant and working with her famous friend, photographer James Olsen, who Grant hired away from Metropolis’s Daily Planet. When Alex’s life was threatened in a plane crash, Kara took to the sky to rescue her. In the aftermath, Kara decided she could no longer sit on the sidelines and came out as Supergirl.