The series tells the story of Sophie Foster, a twelve-year-old high school senior with the ability to read minds. She lives in San Diego until a boy named Fitz Vacker reveals that she is an elf and must leave to go among the elves in the "Lost Cities", a hidden set of cities where elves and other fantasy races live. She has to leave her human family, starts school at an Elvin academy named Foxfire, and stays with an elf couple, Grady and Edaline Ruewen, who later adopt her. She eventually discovers that she has dangerous and illegal secrets hidden in her mind, planted there by the Black Swan, a rebel group who is later revealed to have hidden Sophie originally in the human world. The main antagonist of the series is the Neverseen, an extreme criminal organization.
