The Unexpecteds — Kathryn Judson

Eleven-year-old Shayna Miller lives in the Subterran world, where people hide from the tyrannical government that holds power over the people who live 'topside.' But her Dad keeps moving her family from place to place, almost as if he's running from something inside Subterra itself. But what? Part of The Smolder series. Other books in the series are The Smolder, and The Birdwatcher.