In Brannland, terrifying beasts called Umbrae roam freely once the sun sets, so venomous that a single bite will kill a full-grown adult--and lately, with each day that passes, their population seems to double. The only people who can destroy them are immune children like Nora, who are recruited at the age of seven to leave their families behind and begin training at a retrofitted castle called Noye's Hill. But despite her immunity, Nora's father refused to let her go. Now, years after his death by Umbra attack, Nora is twelve, and sees her mother almost killed by the monsters too. That's when Nora decides it's time for her to join the battle. Once she arrives at Noye's Hill, though, she and her new friends are left with more questions than answers: Where are the Umbrae coming from? Could the government be covering up the true reason their population has whirled out of control? And was Nora's father, the peaceful, big-hearted man who refused to let Nora fight, in on the treacherous secret?