Margot is a Dreg. Because of her dark hair, she's not allowed to attend school, have basic rights like the ability to visit the hospital, or even live in the same house as her family. The ones that do have these rights are called Aryans — a term that has taken on a new meaning to mean people with fair hair and light eyes.
The reason for this separation? A plague that struck the majority of the east coast of what used to be the United States — but only people who didn't have fair skin or light eyes. In the 100 years after the plague, distrust and stereotypes have grown of the Dregs. And it's going to strike this year.
But when a sudden realization shakes Margot's world and that of those around her, she realizes that the explanation might not be so simple after all.