Vietnam gave me the central image for “Graves.” We were airlifted into an area that included a graveyard, which had been extensively shelled. Plenty of moldy old corpses. Very different from the fresh ones we normally dealt with.

I think the uncanny and the horrific are seen most powerfully from the edges of society. Because of this, I often choose narrators who are marginalized in some way, or whose connections to mainstream culture are for some reason tenuous.

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.