There is a moment in almost every haunting movie where an attentive viewer should get suspicious. The demon has been in the house for weeks. It can move objects, kill the lights, throw a grown man into a wall, speak in a voice that seems to come out of the plaster. By any honest accounting it could end the person it is tormenting at any time it wants. Instead it spends the whole film on atmosphere. Cold spots. A door that swings open on its own. A shape at the end of the hall that is gone the second you look straight at it. If the point were to collect a soul, this is a remarkably slow way to get there. So why the theater?

The answer the genre never states out loud is that the scaring is not a means to anything. The scaring is the job. Someone, somewhere back in the machinery, is graded on it.

That is the small observation the book grew out of. Take it seriously for a minute and the demon stops being a monster and turns into something more recognizable: an employee. He has a desk, or the idea of one. He reports to the Hauntings department. He has targets that were set by people who have never crouched in a dark corner at three in the morning waiting for a mark to glance over. He has a craft, and a quiet pride in it, and no acceptable way to voice that pride, because the thing he is skilled at is frightening a stranger in his own home.

I find that situation more interesting than any monster, because it is not really about demons. It is about a very ordinary predicament: being good at work you cannot defend. Most jobs that harm people are not staffed by villains. They are staffed by professionals who are competent, conscientious, and slightly proud of their competence, working inside a structure that points all of that skill at an outcome none of them would choose on their own. The harm is not in the craftsmanship. The craftsmanship is often real and admirable. The harm is in what the craftsmanship is aimed at, and the person doing the aiming rarely gets to pick the target.