Followers of Coville plan to use his journal to create a new Worldkiller. Meanwhile, Supergirl tries to repair the rift between her and Lena, and James is forced to consider whether to out himself or not.

Kara and Mon-El return to Argo City, but not all is as it seems. Meanwhile, in Supergirl's absence, Guardian and the DEO deal with a dangerous gunman wielding DEO weaponry.