Supergirl Season 3 Episode 20 – Dark Side of the Moon
Supergirl Learns A Stunning Secret About Krypton – Supergirl is stunned to discover that a part of Krypton survived. Meanwhile, Alex is attacked while out with Ruby, and Lena considers how far she will go to keep Reign contained.
Directed by: Hanelle Culpepper
Story by Derek Simon & Katie Rose Rogers
Original Airdate: 28 May 2018 (US) / 29 May 2018 (Australia)