Supergirl 3x03 "Far From the Tree" Season 3 Episode 3 Sneak Peek - Eliza (guest star Helen Slater) throws Alex (Chyler Leigh) and Maggie (guest star Floriana Lima) a wedding shower, which causes Maggie to reach out to her estranged father (guest star Carlos Bernard). Supergirl (Melissa Benoist) joins J’onn (David Harewood) on a personal mission. Dermott Downs directed the episode written by Jessica Queller & Derek Simon (#303). Original airdate 10232017.