In the year 1810, two Native-American teenage boys lose a gleaming golden cube from their satchel as they play about in a lake, catching fish. In the present-day Black Hills of South Dakota, two fifteen-year-old boys unearth the same golden cube and think their lives have just been made! Little do they know, the cube attracts evil and their once-quiet, calm little town is quickly getting engulfed by evil shadow beings.
Far beneath Storm Mountain, fourteen-year-old Savannah of the technologically-advanced Annai Civilization, is tired of the constant bullying she faces from her peers for being a half-blood; no wonder she likes to sneak above to the surface and watch the Surfacians go about their lives. It is she who sees the boys finding the cube and must make them be rid of it. But when bullying at school becomes unbearable, Savannah runs away and finds herself befriending the teenagers and their sisters.
Soon, the children find themselves thrown into a prophesied battle in the Annai lands and they must fight together to save their people.