Both Sides Now

S3 E13: The DEO captures a second Worldkiller, Purity (guest star KRYS MARSHALL). Supergirl and Alex use very different methods of interrogation with Purity in the hopes of finding out how to defeat Reign. However, Purity escapes and attacks the city’s subway tunnels. Meanwhile, J’onn, Winn and Mon-El band together to fix the Legion ship.