Maxine and Ceres have never met. Two of the few remaining survivors on Langford's Leap, a human colony world on the brink of collapse, the girls aren't even aware of each other's existence. And yet, together they hold the key to the colony's salvation - or extinction.

Max, a teenager bullied by her fellow colonists for her unusually pale skin and chronic cough, possesses a unique latent ability - she can breathe Leap's poisonous atmosphere. Her genetic mutation is a throwback to the original colonists' gene-tailored bodies, designed to survive Leap's harsh environment. When a genetic mutation caused a near-collapse of the colony, survivors reverted to baseline genetics. Modified humans face ostracism, persecution, or worse.

Far above the planet, Ceres lives alone on a giant space station, with no knowledge of why she is the station's only inhabitant, and unaware of the colonists on the surface below. Her only companion is the habitat's artificial intelligence, an inscrutable machine that relentlessly trains Ceres in the station's myriad functions, but won't - or can't - say why.

When Max and Ceres inadvertently contact one another, they trigger the same chain of events that nearly wiped out the colony a generation earlier. Together, the girls must race to discover the true cause of the original catastrophe, and fight to prevent it from happening again.