Sam Jones and Zoe Miller have one thing in common: they both want an escape from reality. Loner Sam flies under the radar at school and walks on eggshells at home to manage her mom's obsessive-compulsive disorder, wondering how she can ever leave to pursue her dream of studying aerospace engineering. Popular, people-pleasing Zoe puts up walls so no one can see her true self: the girl who was abandoned as an infant, whose adoptive mother has cancer, and whose disabled brother is being sent away to live in a facility. When an unexpected encounter results in the girls' exchanging phone numbers, they forge a connection through text messages that expands into a private universe they call Starworld. In Starworld, they find hilarious adventures, kindness and understanding, and the magic of being seen for who they really are. But when Sam's feelings for Zoe turn into something more, will the universe they've built survive the inevitable explosion?