Mellea Wendorn's world is turned upside down when she stops to help a mysterious stranger who was left to die. By that one decision, she is suddenly swept into the world of the Guardians: the sacred rulers of Selestia. The only way to escape the tyrannic regime of the former Lord Guardian is to agree to unite with Leo, the Guardian's 19-year-old Successor. Mellea is disillusioned by the arrogance of the Guardians, and Leo doubts if he can handle her independent spirit. Mellea's determination to break free leads her to discover that this historic family are far different to what she has been told. With the help of newfound friends, Mellea wants to understand their world, and Leo. When a dangerous enemy emerges from the shadows, only the Guardians have a chance to stop it. And Mellea must make a choice that will change her fate, forever.