In Connolly’s A Book of Bones (Atria/Bestler, Oct.), PI Charlie Parker, his series hero, once again battles supernatural evil.

Where did Charlie Parker come from?

I wish I could say that I had every aspect of his character planned from the beginning, but it would be a lie. I began with a man who had seemingly lost everything. I wanted to write about grief and loss, and how they might be overcome, or at least lived with, but also about the necessity of compassion and our duty toward others less fortunate than ourselves. Yet Parker is not entirely driven by altruism. He recognizes that by acting on behalf of those that suffer, he may find an outlet for his own pain—and, sometimes, for his rage.

What gave you the idea of combining the PI and supernatural genres?

I think most writers are products of their reading, and I’ve always been interested in both genres. When I sat down to write my first novel, what emerged was a combination of the two, which just seemed natural to me. It was only later that I learned this kind of mixing was generally viewed with suspicion by elements of the mystery community, which tended to regard the supernatural as being incompatible with the rationalist roots of the mystery novel. Yet from the very beginning, one can observe an interesting creative tension between the mystery and supernatural genres.

How so?

The Moonstone by Wilkie Collins—often regarded as the first pure detective novel in English—is suffused with a dread of the supernatural, and Arthur Conan Doyle, the creator of that paragon of logic, Sherlock Holmes, believed in fairies and attended spiritualist sessions accompanied by Harry Houdini.

What is the appeal of an imagined world in which there are evil gods who are seeking to enter our world, as in A Book of Bones?

Perhaps it’s because the threats we face as a species—climate change, terrorism, the fear and hatred of those perceived as “other,” whether by virtue of race, color, sexual identity, or religious and political belief—are so god-awfully depressing that there’s almost a kind of consolation in the possibility that a greater, more powerful order might exist, even if it means us no good. It’s the same impetus that drives conspiracy theories: for some people, it’s more appealing to believe that the NSA, the CIA, the U.S. government, or the UN might be capable of organizing and concealing vast, intricate plots than to accept the reality, which is that we exist in a state of disorder—or of order barely maintained—arising out of human frailty.