Sometimes, books have a long gestation period and that was certainly the case for Sacrifice. I think I can probably trace the thought process back to 31 December 1995 when I was sitting in a village square in a tiny town in Austria, watching people waltz in the snow as the town clock struck midnight. And the first line of a novel came into my head: “I danced in the snow as the clock chimed in the New Year; and a monster grew inside me.” Of course I was still a long way from knowing who was dancing, what form the monster would take, how it got there in the first place and what would happen to mother and baby. But I began to think about stories involving a woman, who desperately wanted to be pregnant, conceiving something that was in some way alien and that could, ultimately, destroy her.

Over the next few years, I kept coming back to that story. Probably because of its Austrian origins, I wanted to base the story on a Germanic legend so, one day (fighting back morning sickness) I rolled up at Aylesbury Public Library to research German and Scandinavian mythology. I didn’t find much. But I did come across the fascinating legend of the Shetland Kunal Trows, the race of supernatural males who stole a human wife in order to perpetuate their species. These pregnancies always ended in the same way: a healthy baby boy was born and the mother died. It had sufficient similarities to my own idea to make me want to learn more and I ordered every book I could find on Shetland Legend. And I began to wonder if the story could work as a modern crime novel; could the supernatural elements of the story be sufficiently reined in to work in this strict and sometimes rather formulaic genre. Gradually, the characters began to take shape, as did the storyline. I started to write.

Quite early on I took the decision not to visit Shetland. Partly, my motives were practical: it’s a long trip and I had a very young baby. Mainly, though, I had such a strong idea in my head of what Shetland must be like that I didn’t want reality to cloud it. The Shetland of Sacrifice is the Shetland of my imagination - a remote, wild, fabulous place of incomparable beauty and dark secrets. To help the process along and keep me grounded, I used photographs, Ordnance Survey maps and the internet.

My son was born and I carried on writing whenever I could: he’d go down for a nap; I’d rush upstairs to the computer. Had he been a better, more reliable sleeper in those early days the book might have been finished long before it was. And probably would have been summarily rejected by the market.

Because all the time I was writing Sacrifice, I had massive doubts. I could feel the characters taking life, the narrative was flowing well, but was the underlying story just too far-fetched ever to be taken seriously? No matter how well I managed to write the book, was it doomed to be rejected because of its completely unbelievable plot line?

In this respect I was exceptionally lucky. A year or so before Sacrifice was finished, Dan Brown’s fabulous The Da Vinci Code took the world by storm. Suddenly publishers were hungry for modern day thrillers based on ancient legends and, as I read in The Bookseller, the market started looking for, “… not straight fantasy, but books with a fantastical twist.” The same issue carried a reference to “tapping into tastes for fast-paced adventure with secretive undertones.” The genre had evolved and I was in with a chance.

Armed with new found hope, I sent off sample chapters. Within a couple of weeks, Anne Marie Doulton of The Ampersand Agency offered to represent me and, a month or so later, Sacrifice was successfully auctioned at the 2006 Frankfurt Book Fair.