A thousand years after humanity’s extinction, vampires and werewolves rule the world together. Knox, a vampire baron, and Aurora, a werewolf hunter, are both sworn enemies and secret lovers. To help Aurora win the Festival of the Twin Moons and save his mother, Knox binds their lives together with a forbidden spell—but conceals the truth that every wound inflicted on Aurora will be transferred to him. After losing loved ones and becoming targets of both races, they publicly turn against each other while secretly investigating the conflict. Together, they uncover a conspiracy orchestrated by their rulers, who have spent a thousand years provoking war to preserve an ancient curse. On the night of the final trial, Aurora gives up his only chance to become human and uses the Heart of the Twin Moons to save Knox. In doing so, their forbidden love breaks the curse and gives human civilization a chance to rise again.