Twenty-two years ago, Sam and Dean Winchester lost their mother, who was killed by a mysterious evil force. As they grew up, their father told them about demons that lurk in the dark and roam the country roads of America. And he also told them how to deal with them... Reports of the appearance of a hellish dog and dismembered corpses lead the Winchester brothers to the city of Brennan, Ohio. The capture of a fanged monster turns into nightmarish discoveries. The tracks lead from mad scientists and the latest advances in biotechnology to alchemists of centuries past, legends of walking corpses and an ancient, sinister force. The book takes place during the seventh season of the series, between the episodes "Journey through Time" and "The Soul Vane".