Murder, they wrote...

It's the first in a series of bizarre murders investigated by the California-born forensic scientist Reilly Steel, whom readers first met in last year's Taboo, and who is currently seconded to the Garda Forensic Unit in Dublin.

Given the high-profile occupations of the murder victims in Torn -- among them a journalist, a politician and a judge --should we be tempted to see the book as a commentary on modern Ireland?

"I would say no," says Melissa Hill firmly. "For us the story began with the theme.

"In Taboo the theme was Freud and psychology, and for this one we decided to use Dante's Inferno.

"So that very much then dictates the kinds of murders that are committed," says Kevin Hill, the other half of the husband-and-wife writing duo.

Torn is a novel which explores the extent to which the punishment fits the crime."The punishments in the Inferno were very obscure," adds Melissa, "and it'd be very difficult to bring some of them to a modern-day setting.

"How it ended up being a journalist in the septic tank was coincidental. "I mean," she laughs, "it's not as if we've had bad experiences with journalists ... "

Indeed, the Casey Hill experience has been a very positive one all round. Published last year, the debut novel Taboo was an immediate best-seller in Ireland, and was shortlisted for the Irish Book Awards in November.

It was also snapped up by the TV production company Ecosse Films, with the intention of creating a CSI-style series set in Ireland.

That commercial success should come as no surprise, given that Melissa Hill is a hugely successful author of women's fiction.

So how does writing crime novels compare to that of women's fiction?

"In terms of the difference in writing styles," she says, "I think I can be freer in the crime. Certainly in terms of the characters. There are certain conventions in both genres, as you know, but in crime fiction you can let loose a bit more.

"I think I prefer the collaboration aspect as well," she adds.

"Because if you get stuck writing on your own, you're stuck with that page, but because we talk about this so much it almost feels as if the story's already there, just waiting to come out.

"How many times," she asks Kevin, "have we been on holiday and just spent it plotting and plotting? I mean, really, dinner-table conversation for us is extremely boring if you're with us. And if you're listening, you're probably wondering, 'what the hell ... ?'"

"Yeah," Kevin laughs. "These people seem to have a lot of drama in their lives. But yeah, it's just constant. I could say something or Melissa could say something, and while it might not go anywhere, it might lead off somewhere else.

"Because it's like we're always brainstorming, as such. And that's really worked for us so far."

The Casey Hill pseudonym is a relatively recent development, but Kevin has been a part of Melissa's writing life ever since she first sat down to write her first novel a decade ago.

At the time she had just left a career in banking to work for Kevin's family's business. Living and working in Ashford in Co Wicklow, and with no commute and more time on her hands, Melissa turned to writing, which was something she'd always wanted to do.

Kevin has always been her sounding-board.

"Even though a lot of my own stuff is very straight women's fiction," says Melissa, "there is always an element of solving puzzles in my books, something to be figured out in order to get to the end of the story. So I have to do a lot of double-bluffing in my books, and we were always talking about, y'know, 'how do we turn this on its head?'"

"The only difference now being that people are dying," Kevin grins, "whereas in your books everyone gets a happy ever after."

Torn by Casey Hill is published by Simon & Schuster