In the mountain kingdom of Fontanasia, Avalon Hall is born a girl, but secretly raised as a boy so the king will have a rightful heir to the throne. At fourteen, Avalon is a strong prince and wants only to become king when it is her time, but she is worried that as she gets older, it will be more difficult to conceal her gender. Avalon travels to the distant land of Cormicks, and in unveiling a plot to kill her father, she must survive slow devouring sand eels, gigantic, crushing anthracites, and a terrifying hoard of everred spiders. In a race with time to return to Fontanasia and save her family, Avalon struggles between the boy that she is pretending to be and her growing feelings for Taggerty, one of the king's guard, whose mere presence opens a door in her mind to the possibility of a life she had never before considered.