FOR CRIME FANS THE WORLD over, the North Yorkshire spa of Harrogate means just one person: Agatha Christie, and the real-life mystery that remains unsolved to this day.

On a December evening in 1926 the writer carefully staged an accident, leaving her car hanging over the edge of a chalk pit near Sunningdale, and disappeared. The nationwide manhunt that ensued, which employed aircraft and phone-tapping, is well documented, as is her dramatic reappearance a week later in the Old Swan Hotel in Harrogate.

What happened in the intervening days was never explained. We know that she signed in at the hotel under a pseudonym, but little more. One theory is that she suffered amnesia because of a nervous breakdown after her mother’s death and the breakdown of her marriage. She would never speak of the incident.

But it is appropriate that, 80 years later, the hotel is the venue for one of Britain’s fastest growing literary festivals. From small beginnings four years ago — when an almost unknown Alexander McCall Smith lectured a handful of people on the benefits of somnambulism when pleading not guilty to a murder charge — the Harrogate Crime Writing Festival has become the largest of its kind; the Hay-on-Wye of the crime world.

Throughout the weekend of July 20-23, P. D. James, Jeffery Deaver, Kate Atkinson, Ian Rankin, Martina Cole, Robert Goddard, Mo Hayder and others will sign novels and appear on discussion panels; an award sponsored by Theakston’s Brewery in association with Ottakar’s will be presented for the best crime novel of the year; and aspiring writers can join a day of workshops with authors, editors and literary agents.

As successful crime writers know, the genre is one of the most lucrative areas of publishing, accounting for just over 30 per cent of the total fiction market in 2005 (compared with 5 per cent share for romance and sagas, and 8 per cent for sci-fi and fantasy).

According to a recent survey by Bookmarketing Ltd, Britons bought 20 million crime novels in 2005, spending £130 million. And they are loyal: half of those purchases are prompted by having read novels by the same author or in the same series. Publishers know that once a crime writer breaks into the bestseller lists, their backlists will enjoy a matching rise in popularity.

What is it about crime novels that inspires such loyalty? The genre has changed since Dame Agatha’s days, when the puzzle was everything and characters were just ciphers in a plot with devilishly clever twists and turns. Now, as admirers of John Rebus, Harry Bosch or Precious Ramotswe will testify, the process is more organic — a blend of forward-driving, suspenseful plots that ask and resolve questions, strong, believable characters, atmospheric locations and hard-hitting social commentary.

But one thing hasn’t changed. In crime fiction, everything happens for a reason. If a peripheral character is knocked down in a hit-and-run accident, we know that, in the course of the narrative, the driver will be bought to book and, perhaps most importantly, we’ll learn why the accident happened.

There may not be a happy ending, but the conflict will be resolved, and that resolution will be made more profound by the gradient of the narrative arc, the dangers inherent in the questions asked and the personal traumas endured by the hero.

In Kate Atkinson’s new novel, One Good Turn, a wonderful jeu d’esprit set around another festival — Edinburgh — a series of apparently random events are brought together in an entirely unexpected denouement. The main character learns more about himself than he might care to, and the reader feels sympathy, fear and pity for his plight before that all-important release as the last piece of the jigsaw falls into place and the mystery is solved.

I like to think that Dame Agatha would have approved. She would, I hope, be happy to find the genre in such fine fettle. She might also be pleased to discover it being showcased in the hotel where she made her reappearance 80 years ago. www.harrogate-festivalorg.uk/crime

Selina Walker is a publisher at Transworld, whose authors include Kate Atkinson

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