Sixteen-year-old Koral and her older brother Emrik risk their lives each day to capture the monstrous maristags that live in the black seas around their island. They have to, or else their family will starve.

In an oceanic world swarming with vicious beasts, the Landers-the ruling elite, have indentured Koral's family to provide the maristags for the Glory Race, a deadly chariot tournament reserved for the upper class. The winning contender receives gold and glory. The others-if they're lucky-survive.

When the last maristag of the year escapes and Koral has no new maristag to sell, her family's financial situation takes a turn for the worse and they can't afford medicine for her chronically ill little sister. Koral's only choice is to do what no one in the world has ever dared: cheat her way into the Glory Race.

But every step of the way is unpredictable as Koral races against contenders who have trained for this their whole lives and who have no intention of letting a low-caste girl steal their glory. When riots break out and rogues attack Koral to try and force her to drop out, she must choose-her life or her sister's-before the whole island burns.