“Saturn Girl is the heart and soul of the Legion of Super-Heroes. When everybody’s saying, ‘Legion doesn’t work anymore. There’s too much xenophobia. You can’t change people.

“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 ...