Supergirl 4×15 “O Brother, Where Art Thou?” Season 4 Episode 15 Sneak Peek – JON CRYER GUEST STARS AS ICONIC DC COMICS’ VILLAIN LEX LUTHOR — Secretly furloughed from prison due to failing health, Lex Luthor (guest star Jon Cryer) visits his sister, Lena (Katie McGrath), to seek her help finding a cure. Savvy as ever, Lena is suspicious of Lex’s motives but when she’s faced with a life and death situation, she must decide how she truly feels about her brother. Meanwhile, Supergirl (Melissa Benoist) and J’onn (David Harewood) face off against Manchester Black (guest star David Ajala). James’ sister Kelly (guest star Azie Tesfai) comes to town. Tawnia Mckiernan directed the episode written by Derek Simon & Nicki Holcomb (#415). Original airdate 3/17/2019.