I wrote this story about eight years ago, and, though I loved the premise, couldn’t make it work. Then, about three months ago, I realized the problem. I’d been skating the line between psychological and true horror—I’d never answered whether it was all in Mary’s head, or a true haunting. Once I answered that question, I could move forward.

A story of any sort has a psychology, and beyond that it’s just a matter of degrees.

I’ve always been interested in world mythology, especially Norse. Late in 2011, I packed up my faithful hound Athena and drove an old truck pretty much non-stop from Montana to New York State. The story came to me as I visited a rest stop in Wyoming—two a.m. and a winter breeze rolling out of the Bad Lands.

As much as I make a living writing about things that go bump in the dark, I don’t particularly fear them. Ghosts have very little track record for doing much harm, and I’m not afraid of a spirit that would slam a door or change the temperature in a room. Big yawn. Fictional spirits are different in that they are vehicles in which we can tell different kinds of stories.