AND relax.

When last month's Commonwealth Games concluded Alex Gray admits she breathed a sigh of relief. Mostly because the crime writer's most recent book The Bird That Did Not Sing was based around the idea of a terrorist threat to the Games and so when the real-life event passed off without incident she didn't have to worry about being labelled a Cassandra. "I had every faith in the security services," she says now. "I really did."

But then it's the job of a crime writer to think the worst, and Gray has been doing just that for more than a decade now while chronicling the investigations of Glasgow's Chief Inspector Lorimer. In other words, she spends her days writing about bloody murders, everyday brutalities, unthinkable horrors. And yet she seems such a nice woman.

"There's always been a darker side to me," she laughs as she serves me coffee and a slice of banana and walnut loaf. "I've always had, as my parents would put it, a 'morbid curiosity'." We are sitting in the kitchen of her Bishopton home. Her husband Donnie is tinkering about elsewhere in the house keeping an eye on their new kitten. Classic FM is playing on the radio. It's all cosy. Not something you could say about her books.

I've come here to ask her about evil. On her website Gray says she believes it exists. She says the same in person too. "I had a big conversation with (Norwegian crime writer) Gunnar Staalesen at the book festival about this. Gunnar does not believe evil exists. He believes every single murderer commits their act from a position of a mental health defect or social engineering. But Agatha Christie believed there were evil people in the world and so do I."

Can she define the word for me? "I think my definition of evil is the decision to carry out a very evil act knowing what you're doing, completely aware of what you're doing, knowing what the consequences will be for the person that you're attacking and not having a mental illness. An evil act is one that is definitely premeditated, considered and ruthless."

It's also completely different from a crime of passion, she points out. She's a regular prison visitor to Cornton Vale, "and so many of the women there, I'm sure, are guilty of crimes of passion. So many of them are pitiable. I just want to take them all home with me. But I do believe there are bad people. And I don't think you can make the excuse that they are all psychopathic."

It's not a fashionable idea, she admits. But then she adds, "it's also not fashionable to talk about the devil." Well indeed. Around her neck hangs a cross. Her ideas, it's fair to say, have been shaped by her faith. "I'm quite certain of it. Scripture does tell us that evil exists." The question, then, is does she consider the crime novel - or her crime novels at least - a moral form? "Absolutely. You're showing the triumph of good over evil."

That doesn't always happen in real life of course, but maybe, she thinks, that's why people love crime fiction so much. "I think readers and writers can put their worlds to rights. We live in an age where we don't have a lot of power. We can only make a small difference by putting a cross on a bit of paper every five years. A writer of crime fiction can create a world over which they have total control. The reader can read this knowing that there will be a satisfactory outcome, knowing that justice will be done. Nemesis is important. You have to have a sense of resolution."

Gray is 64 now. Her first book was published when she was 52 but she'd always wanted to write, indeed had written short stories, and the odd article for this very paper. Still, she had a varied career before becoming a full-time crime writer. As a student she earned money as a folk singer and after university she joined the civil service and worked in the DHSS - as the DSS was then known - visiting claimants in Govan. "My area was old Govan, including Wine Alley before they modernised it. So you had rat-infested places with water running through the walls. It was unbelievable. It was Dickensian.

"I was wet behind the ears and I found I was taking my claimants' lives home with me and worrying about them and losing sleep." Eventually she decided to re-train as a teacher, a job she loved until the early 1990s when she was struck down by illness. "It was eventually diagnosed as ME. I couldn't stay awake, basically. Not a good time. My poor wee daughter bought me a big rug for Christmas. I think she thought I was dying."

She attributes some of her eventual recovery to alternative practitioner Rosalie Dickenson of the Rapha Centre in Perthshire. But, as she says, you never lose ME. "But you can control it. "

It was while she was recovering that she started writing again. The first Lorimer novel finally appeared in 2002, seven years - and 11 publishers' rejections - after she started it.

Now Gray is a fully paid-up member of the Tartan Noir tendency and has even been instrumental in setting up Stirling's crime writing festival, Bloody Scotland. Words are her world. They always have been.

"You lose yourself in a good book. That's what I tell the prisoners. The first thing I say is 'I've got your get out of jail free card. Come into the imaginary world of fiction'."

The Bird That Did Not Sing is published in paperback by Sphere, priced £7.99 on September 11. Bloody Scotland opens on September 19. Visit bloodyScotland.com for details