Seventeen year old Ollie Miller is ready to leave all of her hurt feelings behind, but moving on seems impossible while living next door to her ex-best friend, Mateo. When curious earthquakes begin to shake and rip open the foundation of her small town, the ground becomes as unsteady as her feelings for him. When they fall, they fall hard... Ollie's disastrous attempt to save Mateo's brother from falling into a curious chasm results in their descent into a cavernous wonderland. Ollie, Mateo, Jesse, and Alexis search for a way back home, and encounter a mysterious tribe of natives. Gabriel, the next in line to lead his people, is granted permission to guide them to the surface. On their treacherous journey, an overzealous elder threatens all of their lives, because he can't risk them exposing his people, or the power he wields. The group discovers ancient secrets, unexpected truths, and uncharted feelings. Ollie must find a way out or risk being stuck in the caves forever-or worse, dead.