Mare Barrow, of lowly red blood, is given a job in the royal palace to serve those with silver blood and supernatural powers. One day in front of the king, Mare discovers she has her own unique power. The king tries to hide this fact by calling Mare a lost Silver princess and betrothing her to one of his sons. In spite of this, Mare risks everything to help the Scarlet Guard, a rebellion against the Silver elite, and puts herself in grave danger.