Everyone knows about the thirteenth floor in Mortagaine House - or thinks they do. They've heard the stories. But they don't know what's really up there, a living, breathing thing, feeding on the hopes of the town, taking their souls and leaving an empty void behind their eyes. Bee and Dino haven't spoken for years, but when Bee overhears her dad saying he's given his soul, she knows only Dino can help her fight this creature. He has a book - the Rules of Magic - that can fight it. It's more difficult than they think, when they're offered everything they could have ever wanted, to hold on to their souls and not go back for more. But ultimately, only they can stop the creature taking over the city, and making them, and everyone in it, less than human.