Which one is the real monster? Celia Ashleigh, otherwise known as The Fox, is a powerful shapeshifter and spy-in-training, like other firstborns in her family. Remy Broussard's family are werewolves. And the Guardian of La Cluse is on a crusade to wipe out monsters like them. He's kidnapped Remy's little sister and plans to kill her when she changes for the first time on All Hallow's Eve. When Remy begs for help, Celia doesn't hesitate. But the closer she comes to finding the madman and his captive, the more dangerous her task becomes... and the more hopeless. What will happen if she makes a mistake and the hate-filled Guardian discovers Celia is something more than human, too?