Following the events of Pulse Point, 12-year old Ama and the other
Underlanders living in a world of darkness dig for brine, the City's
real energy source. Underland is a dangerous place: cave-ins, starvation
and illness are constant threats. When their leader deserts them, Ama
goes looking for him and stumbles on two Citizens. Neither knew the
other existed. 18-year old Sari lives in the City, blissfully unaware of
what goes on beneath her feet. The disappearance of her best friend,
Kaia, has left her feeling isolated. A chance encounter with her sister
leads her to join a group called the Resistance who are on a secret
mission to reveal the secrets the Council keeps hidden. When Kaia mounts
an attack on the City, Sari and Ama are thrown together in a battle that
will decide their futures and the fate of the City.