Maren, a student at a school for witches, is framed and killed during a zombie apocalypse. She is reborn, returning to the night of the "Spirit Beast Pact"—only to have the creature meant for her snatched away by a rival who has also been reborn. Left with no other choice, Maren forms a pact with Aurel, a white stag wreathed in thorns who appears to be utterly useless. As a fungal plague—the source of the zombie outbreak—closes in, Maren awakens a latent resonance tied to her family’s ancient blood pact. Together with Aurel, a boy named Rook, and other allies, she sets out to confront Cassian, the mastermind behind the chaos, and thwart his sinister plot to seize control of the zombie hordes and an army of spirit beasts by harnessing the power of the blood pact.
