A strange but compelling manuscript, supposedly the memoir of a Church of Scotland minister who has gone missing, arrives on the desk of an Edinburgh publisher. It tells the story of Gideon Mack, a son of the manse raised in chilly austerity and dominated by a joyless father, who claims to have met the Devil. Mixing fantasy, legend and history, The Testament of Gideon Mack is an ambitious, mesmerising novel which combines superlative storytelling with immense imaginative power.

Prologue

In presenting to the world the following strange narrative, I find it necessary to offer a word of explanation as to its provenance. Being a firm believer in the principle of the division of labour, I do not usually divert myself from the business of publishing books in order to write prologues to them. However, Mr Harry Caithness having declined to provide an introduction - on the grounds, he says, that he has more than cancelled any debt he owed me by (a) sending me a copy of the original manuscript in the first place and (b) submitting the report which forms the bulk of the epilogue - I am left with no option but to write this myself.

Sir Walter Scott, with whose work, as you will read, the Reverend Gideon Mack was intimately familiar, once described publishing as 'the most ticklish and unsafe and hazardous of all professions scarcely with the exception of horse-jockeyship'. I have this salutary warning typed up on a three-by-five inch card taped to the wall beside my desk. Whenever I fall to wondering why I persist in trying to make a living in this profession, and whether some other form of gambling might not offer a greater return for less effort, I read those words of Sir Walter - penned long before he himself fell so heavily at the high fence of publishing - to remind myself that it was ever thus. Then I take a deep breath and carry on.

So it is with this book. One voice in my head tells me that it is a mere passing curiosity in which few will have any interest; a waste of my time, the printer's ink and the forests of Finland. Another whispers that it is outlandish enough to attract a cult readership, if only that readership can be identified. A third - the voice, perhaps, of my conscience - deplores the exploitation, for commercial gain, of the outpourings of a ruined man. A fourth loudly protests at this: the man is dead and therefore cannot be exploited, and the book, though some may dismiss it as a tissue of lies or the fantasy of a damaged mind, is a genuine document with its own relevance for our times. All these and other arguments have jostled in my brain when I have pondered Gideon Mack's story. In the end, what has persuaded me to publish it is its very peculiarity: in twenty years, I have come across nothing like it. It is not a fiction, for Gideon Mack undoubtedly  existed; yet nor, surely, can it be treated as fact. What, then, is it? It is because I am unable to to answer this question that I consider it worthy of the public's attention, so that others can make up their own minds. But first I must recount how it came into my hands.

One Monday morning at the start of October 2004, I received a phone call out of the blue from my old friend Harry Caithness. I was sitting at my desk sipping my third coffee of the day, turning the pages of the latest edition of our Scotch whisky guide, A Dram in Your Pocket, newly back from the printers. It looked very handsome, all the more so for being a reliable mover, and I anticipated some healthy sales in the run-up to Christmas.

I had not heard from Harry for a while, but I recognised his gravelly voice at once. He is a freelance journalist, based in Inverness but roaming from there east along the Moray Firth, and to Fort William and all points north and west. He picks up stories of every kind and sells them to the highest bidder. He is what one might call - and I hope he will take this as a compliment - one of the old school. He smokes, drinks too much, eats unhealthy food at unhealthy hours and doesn't respond well to sunlight. But he is a first-class reporter, hard-headed enough not to let go of a good story yet sensitive enough to deal with people in such a way as to secure it. He has also written a book, Crimes and Mysteries of the Scottish Highlands, which I published. It has done very well over the years. I paid Harry a decent advance for it, and twice a year he still receives a royalty cheque, which, as he says, would pay for a week's holiday if he ever took one. To me it is business, but Harry used to say, when we spoke on the phone, that he owed me something. He doesn't say this any longer.

I asked him how he was, and he said he was fine. We might at this juncture have exchanged further pleasantries along these lines, but Harry doesn't do pleasantries. Instead, he came straight to the point. He had something for me, he said. It was somewhat sensitive, but he thought it would be of interest. Had I ever come across a character called Gideon Mack?

The name rang a bell, but I couldn't place it, and I said so.

'He was a minister,' Harry said. 'Church, not state. He went missing earlier this year.'

He reminded me of what had happened. There had been quite a bit in the papers at the time, and as Harry talked I recalled some of it. The Reverend Gideon Mack had vanished from his Church of Scotland manse one day in January, and nothing had been heard or seen of him since. Before his disappearance Mack had gone spectacularly off the rails, causing something of a stir in Church circles and in Monimaskit, the small town on the east coast which was his charge. I suspected that Harry was going to tell me that he had turned up and wanted to sell me his life-story - a prospect, I confess, that did not fill me with eager anticipation - but I was wrong. Mack was still missing, but something of his had turned up, and Harry said he thought it had my name on it. When I asked him what he meant, he said, 'Well, it's something he's written. A kind of memoir, or a confession, I suppose you'd call it. I think you should take a look. I read it over the weekend. I'm going to stick it in the post to you.'

I asked him how he had got hold of it, and what exactly Mack had confessed to. 'Quite a lot, for a minister,' Harry said. 'Adultery, for example, and meeting the Devil.' This second item also rang a bell. I asked Harry again how he had come by the thing.

'One of my contacts in the Northern Constabulary photocopied it for me,' he said.

'That was decent of them,' I said drily. 'Why did they do that?'

'Never you mind,' Harry said. 'I'm a journalist. I have to protect my sources.'