I asked him which little dolls he meant. He winked, and told me to take the lift to the fourth floor. Plenty of people over the years have come up to me with their excited notions of plots for my next book. I’ve found precious few of them to be helpful or viable, but I was intrigued by these ‘little dolls’… which is how I made the acquaintance of the Arthur’s Seat coffins. They’re tucked away at the back of the fourth floor, in a section dedicated to religious belief and the afterlife. As soon as I saw them, I knew they would make a great story, especially as no one had come up with an incontrovertible interpretation of their meaning. In other words, there was a story to tell about them. Maybe fiction could provide a sense of closure which so far had been lacking from their history.

There must be a story behind all that …

My books have always been attempts to explain aspects of Scotland to both outsiders and natives. I like using ‘hidden’ stories – Mary King’s Close (Mortal Causes), cannibalism (Set in Darkness) – as my starting points. There are things you can say in fiction which can’t always be contained by history books. It’s true also that I take real-life unsolved crimes (such as the Bible John murders in Black & Blue) and extrapolate from them to say something about the world we’ve made for ourselves. Maybe that’s why I became so intrigued, soon after my experience with the Arthur’s Seat coffins, by the story of Emmanuel Caillet, a young Frenchman whose body had been found on a Scottish mountainside. No one could explain why he’d come so far from home in order to kill himself, or even why he would kill himself. One theory – no wilder than many of the others – had it that he was involved in an Internet role-playing game, and that this had led to his murder. The perils we face when going online have been well documented, of course. Cyberspace is the perfect haunt of creeps, charlatans and hunters. It’s a place full of shape-shifters.

Moreover, it’s a place beyond Rebus’s ken.

I knew that by using role-playing as the basis for a plot, I would be taking Rebus into new territory, to a place where he would feel utterly lost. In other words, it was a way of allowing Siobhan to show her mettle. This would be her case, an opportunity for her to prove she’s as capable a detective as her mentor, but with a different set of skills. Meantime, I would give Rebus a quest of his own, but with physical clues – the dolls – rather than hi-tech ones.