“Legion of Super-Heroes” begins with Kara waking up to a knock at the door. She opens it up and is introduced to Brainiac 5, who’s been sent by Mon-El to check up on her.
It’s revealed that Kara is still in a coma from her run-in with Reign in the midseason finale, and Brainiac 5 is able to project himself into her consciousness to check up on her. Kara briefly forgets about her battle with Reign, and once she remembers, she attempts to wake herself up so she can fight Reign.
Brainiac 5 leaves Kara’s consciousness and informs the group of Mon-El, Imra, J’onn, Winn, and Alex that although her brain is in good shape, she’s very upset.