A strange encounter with a Fey shapeshifter on a Bosnian battlefield thrusts Will Kirwan into the middle of what he thought was a family legend. But the legend proves true, and now he must come to the aid of the ancient Fey King on a world untouched by humans. Three-hundred-year-old Soutien, half-Fey, half-human, returns to the Kirwan estate only to discover that all four of his charges, including the only woman he has ever loved, have been lured into the Fey world. In a place of tortured tree nymphs and madness, Will and Soutien must fight off the deadly Fey who want to kill them, find Will's siblings, and make their way to the King... all while war brews between the Seelie and Unseelie courts. They will risk everything-love, honor, and life-in the name of an oath taken centuries earlier. But will it be enough to stem the tide of a war that would destroy both worlds?