A woman with early-onset dementia discovers her neighbors are cannibalistic cultists while tending her garden in Brogden’s Bone Harvest (Titan, Nov.).

What drew you to write about cults and Celtic mythology?

Well they’re a staple of horror fiction, aren’t they? The facetious answer is that I’d written about bog mummies and plague zombies and ghost witches, and cults were next on the list. But it actually evolved out of wanting to write a story set in an allotment garden. And once you start following the thread of nature worship, seasonal rituals and the like, you get to fertility cults pretty quickly.

Tell me more about why you set the book in an allotment garden.

The thing with allotments is that, first of all, they are a quintessentially British obsession, and there’s nothing I love more than exploring the idiosyncrasies of my fellow countrymen and women. The other thing is that they are gentle and harmless, and the part of me that likes to cause—very mild—trouble can’t help but imagine that there’s something sinister going on. They’re almost too nice. What’s in all of those sheds, for example? Just tools? You’re not going to tell me that somebody never tied up a person in one of them. Or that nobody dealt a little home-grown herbal tobacco to the neighbors. Some of the news stories I researched about allotment crimes made my toes curl, especially the one about the man with the goat. That’s all I’m saying.

Your depiction of Dennie’s early-onset dementia is incredibly nuanced. How did you approach her mental state?

It helped that one of my editors had it in her family history, so she was able to steer me away from some clichéd representation and point me towards the reality of how it develops and is treated. I’ve been fortunate so far that I’ve never had to deal with it in my own family, so just lots of research, really. I tried to imagine what kind of an irascible old fart I’d turn out to be and coupled that with my own personal fear of mental disintegration, and I guess I’m close enough to both that it comes across as legit. Which is nice, but also worrying.

How did you balance the novel’s dark humor with the suspense?

I think it’s an inability to take myself seriously, and especially a tendency to distrust or just get easily bored by people who do. So if I’m creating a situation which is pretty extreme there’s always that tiny voice in the back of my head saying, “You do realize that this is utterly ludicrous, don’t you?” And I think my characters would probably feel the same way too. It can actually make it scarier because yes, this thing is ludicrous, it should not be happening—but it still is. Fear and laughter go together as a fundamental tug-of-war.