From the day 15-year-old Caryn Tobin watched her best friend drown, she has carried two weights: a fear of water and the responsibilities of the oldest candidate in the Compound, a leading power on Beta Earth. Caryn is determined to live up to her friend's memory, even if it means forcing herself to train in the water every day in order to protect the other girls so they can live and dream.
After nearly 3,000 years on the first colonized planet, there is still a deadly toxin in the air poised to wipe out the world's population and it is the Compound's purpose to train candidates from birth to gather the underwater cure. All the candidates compete for the chance to save the world, but only one can win and the winner will not survive collecting the cure. Caryn has to win. It is the price she must pay to atone for her part in the drowning.
Yet moments after sealing her own fate, Caryn is offered an opportunity to see the planet and leave the Compound for three days. In the city she meets Kai, a 16-year-old street kid, who is searching for answers to his past. They form an unlikely friendship and Caryn realizes she has dreams of her own. Her decision is further complicated when she discovers the Compound has been experimenting on the very people they are sworn to cure. Now she must choose between her sense of duty and her heart, with the fate of the world hanging in the balance.