Murder most foul is afoot again as Anthony Horowitz’s quirky characters return in “Moonflower Murders” on PBS. “Moonflower Murders” and the original series, “Magpie Murders,” are based on Horowitz’s books and, yes, there’s a third on the way.

“This one is called ‘The Marble Hall Murders,’ ” he says. “It is a variation on the theme, and the book has been extremely well-received by my American publishers, my Canadian publishers and my British publishers, and, most importantly of all, by my wife,” says Horowitz.

Most conveniently, Horowitz’s wife of 36 years is Jill Green, who serves as executive producer on the shows and, as he says, proves a trusted editor.

“We started collaborating on ‘Foyle’s War.’ It was the first show we did together,” Green says.

“I guess it gives us a fantastic shorthand. When we’re working on these very complex shows, where things change all the time and we have to think outside the box, sometimes very quickly, to have that tremendous work ethic is fantastic. I mean, we can still argue in a room, we can still not agree because we come from different sides of the coin sometimes. But I love it.”

The complexity she’s talking about is the fact that the narrative of the plot moves between two worlds: the real world of a book publisher and her alter-mentor, a peerless detective from a 1950s novel — a gumshoe that only she can see. This is easy enough in book form, but not as simple for television.

Even though these three novels are beleaguered by crime, Horowitz insists his work is not dark.

“I think what I write is entertainment and very life-observing, but I guess that the darkness in them, the murders and the violence and the sense of threat comes from my own childhood — those unhappy days between 8 and 13 that have never quite gone away.”

Those unhappy days marked the period when Horowitz was sent away to boarding school by his parents. “I was extremely unhappy there because if you were in English boarding school back in the 1960s you had to be one of two things: very clever or very athletic. And I was neither,” he recalls.

“Two things changed everything for me. The first was my discovery of the library. The school had a library, and that was my place of refuge and books became an escape for me — just reading adventure stories and absorbing them and living them and at the same time, I discovered the ability to tell stories. So in the dormitory at night I would tell stories to the other kids, and suddenly I was popular because they enjoyed my stories. That was a transformative moment in my life. I was 10 years old, and I knew I was going to be writer and there was no Plan B.”

Horowitz has also scribed the Alex Rider series about a teenage James Bond, and he has dallied with Sherlock Holmes and written the addicting “Foyles War,” about an uncompromising small-town detective during World War II. Though the writer, 69, was too young to remember the war, he says he had a nanny as a child who regaled him with wartime tales which piqued his interest.

“I’m fascinated by writers,” he says. “I think about Conan Doyle. Arthur Conan Doyle created Sherlock Holmes, the greatest detective who ever lived, and dislikes him so much and feels he’s so far beneath him, that he throws him off a waterfall at the Reichenbach Falls. ... I find that fascinating in writers who create great characters and then feel that they’re somehow beneath them.

“That is not true for me. Every character I’ve created from Alex Rider to Hawthorne to all the characters in this show, I love. I love my work. And I don’t have any sort of views of myself as being too good for this. I love murder mystery writing.”

The six episode “Moonflower Murders” airs Sundays on PBS.