Supergirl 6×16 “Nightmare In National City” Season 6 Episode 16 Promo – NIA CONFRONTS HER SISTER – Kara (Melissa Benoist) lands her dream story for Catco but when the city is suddenly attacked by a nightmare monster at the same time as her interview, she is forced to take a serious look at her life and decide if she can continue to live as both Kara and Supergirl. As Dreamer (Nicole Maines) takes the lead on the search for the Dream Totem, which can vanquish they nightmare monster in National City, she realizes she needs to ask her sister Mauve (guest star Hannah James) for help. Old wounds resurface as the two sisters come face to face. The episode was directed by Eric Dean Seaton written by Rob Wright and Jess Kardos (616). Original airdate 10/19/2021.