After Cassidy Ravanaugh's boyfriend Jace dies she goes to find a ring that he had been wearing. but get gets more than she bargains for when she goes through a gate to a different realm with demons and Demon Hunters. Killian the Demon Hunter that is hunting for Cassidy's boyfriend, who ends up a demon, and the other demon hunters and sects doesn't have an explanation on how she crossed over there in the first place. as the story goes on we find out that Cassidy's Ring is special and so is she and that the Demon Hunters are preparing for Battle. who will win this war you have to read the books to find out.