The Exile Waiting

The time is the distant future and Earth has been rendered uninhabitable by terrible storms during which its only city, Center, constructued around a natural cave system, is sealed from the outside. Mischa, a young theif whose capabilities are enhanced by hereditary mutation, is trying to escape with her drug addicted brother from the dominance of her uncle. So when a starship arrives, commanded by the twin alien pseudosibs, Subone & Subtwo, Mischa seizes her chance. All goes well until Subone, in a moment of cruelty, lures Mischa's brother into a fight and kills him. Mischa exacts her revenge, but has to flee the wrath of the aliens and take refuge back in the deep caves underneath the city.