Ajax Holdren didn't think his life could get much worse, until a pretty girl with a sword decided to fight a monster right outside his house. But it turns out the monster is after him, and she's what passes for a guardian angel, a Nightlight-- and Ajax is potentially the most powerful Nightlight ever. Once Ajax meets Natalie, he can't go back, can't pretend the monsters aren't there. But going forward takes him into a world beyond imagining, where the walls talk and the sun never shines, and the mankind's worst enemy isn't the monsters who stalk the street but the people who make them.