How health scares fuelled author Paul

Then came the dark day when he was diagnosed with cancer. It cost him a kidney. Just weeks after receiving the all-clear came a second cancer diagnosis. This time it was a tumour "the size of a tennis ball" in his bowel.

You might think that two unconnected bouts of the deadly disease within five years would have stopped him from writing, especially as the second came at the same time as he was dropped by his publisher.

Instead, it drove him to create Matt Wells, a new, bitter and twisted lead character for a series of thrillers that reaches its third instalment with the publication of Maps of Hell.

"Having spent a lot of time thinking about life, death and anything else that you care to mention when I was ill, I needed a protagonist who reflected my state of mind," says the 53-year-old, who made his name with a private investigator boasting an Orwellian Edinburgh of the future as his beat.

Maps of Hell, in which the central character escapes from a secret Nazi-style militia only to find himself in the frame for a series of gruesome murders, is a stand-alone novel in the Wells series. Unlike predecessors The Death List and The Soul Collector, the story unravels in the United States. It was a real challenge for the writer.

"The first two books were set in London and I thought I'd gone as far as I wanted with that," explains the Fettes College old boy, whose old man, Ronald, was a successful thriller writer.

"Plus, there's my general interest in American crime books and crime movies, so I thought I'd shift it over to the States."

Doing so presented plenty obstacles to overcome.

"For one thing, there's the location," he explains. "Then there's the language - the whole American-English issue. Fortunately, my editor is based in New York so he helped to do some work on that. Not that what I did in the first draft was a disaster . . . Your ear becomes attuned from watching American cop shows and all that."

As a lifelong admirer of American crime behemoths Raymond Chandler and Dashiell Hammett, Johnston felt that he was moving into sacred territory by setting his novel Stateside.

"You're always very aware of the ghosts of the past," he says, "so that was quite a challenge for me psychologically. Readers will judge for themselves, but I think that I pulled it off."

It certainly sounds like America got his creative juices flowing, but Johnston isn't ruling out Edinburgh as a location for future books.

"No, I'm not done with Auld Reekie just yet. I think with all the changes that have happened in the city over the past 25 years - some of which I accurately predicted, much to my own surprise - it would potentially provide quite a lot of material for going back to it."

Johnston came late to literature himself. After schooling at Fettes, he went on to study ancient and modern Greek at Oxford University. He graduated in 1982 and worked for shipping companies in London, Belgium and Greece, before a journalistic stint at a newspaper in Athens. Taken by the Greek way of life, in 1989 he went off to teach English on the small Aegean island of Antiparos. It was then he started to write seriously.

It wasn't because of any great desire to follow in his writer father's footsteps that he did so, but rather a feeling of nostalgia for his hometown.

"I was living in Greece, in supposedly an idyllic situation on a wee island at the time, but Edinburgh's such a spectacular city and, even if you've grown up there or spent a lot of time there, you do feel that you want to go back.

"Even if not necessarily full time, you know? So it did have that hold on me and it still does in many ways."

Johnston, who finished his chemotherapy in 2008, now lives in Athens with his second wife, Roula, a Greek civil servant, and their two young children. While he still considers Edinburgh his home, it's unlikely that he'll ever move back here permanently.

"I've not really done that because, having written the books and so on, it's become such an imagined city to me," he says. "Living in Edinburgh would not make it easier to write about it because then you're up against the reality and that wasn't ever my thing."

Of course, detective stories set in Edinburgh are nothing new. Ian Rankin's Rebus series is the most obvious example, but with others like Quintin Jardine and Allan Guthrie also using the Capital as a canvas for tales of blood and gore, you'd be forgiven for thinking the city was a murder hotspot akin to James Ellroy's Los Angeles or George Pelecanos' Washington DC.Edinburgh isn't notorious for high levels of crime, though, so why is it that drug trafficking, murders and hunting down master criminals in the Capital's seedy underworld are part of a day's work for the city's many fictional investigators?

"I think that you get encouraged by the fact other writers have done it, but in some ways that means it becomes harder because you have to find ways of using the same locations but getting a different angle, otherwise it's all the same.

"That's maybe a reason I moved out of Scotland in the first place, because I felt there were so many other people doing it. I'd found my angle and I didn't really feel I could be bothered to find another one."

• Maps of Hell is out now, published by Mira, priced 6.99

Following in his thriller writer dad's footsteps

PAUL Johnston was born in Edinburgh in 1957. His father, Ronald Johnston, was a successful thriller writer.

After working in shipping and for a newspaper in Greece, he started writing seriously in 1989, a year after his daughter Silje was born. His first novel, Body Politic, won the Creasey Dagger for best first crime novel in 1997.

In 2005, he married his second wife, Roula. Their daughter, Maggie, was born in 2006 and son Alexander in 2008.

Maps of Hell is the third book featuring Matt Wells. It has been described as "a cross between The Manchurian Candidate and The Bourne Conspiracy".