Supergirl remains in a dreamlike state after sustaining injuries from Reign, so Mon-El recruits Brainiac-5, a member of the Legion of Superheroes, to bring her back.
The battle with Reign has put Supergirl into a coma like state to try and heal. Brainiac-5 enters into Supergirls coma-dream and tries to explain to her that she has sustained so much injuries that her body is healed . While she is fine physically in a Legion Healing tube, its up to Supergirl to wake up or she will remain in a coma and die. The DEO has tried to subdue Reign but are having trouble without Supergirl. Will Mon El help the team? What is the secret that he is protecting? Why is Thomas Coville now helping Reign?—Movie Dude