New viruses and organisms created by geneticists have entered the wild and wiped out edible plants, animals and most of the population. For years now, a select portion of humanity has been hiding in fortified cities called citadels, while the rest of us survive by buying seeds programmed for only one harvest. Thirteen-year-old Vesper lives with her paralyzed father and conducts experiments, breeding new species of plants and trying to crack the seeds' genetic code. One day she helps a woman injured in a glider crash and decides that she will help her get to the citadel.