Anatomy of melancholy: Belinda Bauer's chilling crime mysteries have caused a sensation

Belinda Bauer, a small but seemingly courageous figure as she navigates Cardiff traffic, has a surprising fear: she hates going into water. It stems from her childhood in South Africa where her father knew three people who had been attacked by sharks within the space of six months. "One had an arm bitten off, one was an old lady – all they found was her swimming cap – and another was a young spear-fisher who was swallowed all the way up except for his head. For years after that I didn't like going into a swimming-pool."

But as a writer, Bauer uses her experiences. "I think as a crime-writer you really have to understand fear," and the creeping apprehension of imminent horrors is a notable feature of many of her characters. It certainly distinguished her first novel, Blacklands, in which a young boy tries to find the body of his uncle, buried on Exmoor by a paedophile murderer. Blacklands won the Crime Writers' Association Gold Dagger in 2010, but also shocked some. It is unsparing in its description of the poverty, spiritual and physical, of the boy's home.

Bauer, whose father was a dentist, herself experienced a sudden dive from a wealthy home in South Africa to a poverty-stricken West Country household when she and her mother returned to Britain. The dedication of that first book was "To my mother, who gave us everything and never thought it was enough". Bauer presented a realistically harsh picture of English village life in the fictional Shipcott. She also defied the conventions of the "cosy" crime novel in the second Exmoor novel, Darklands, where the policeman's wife, Lucy, suffers from MS but is no plaster saint. Had Bauer studied much crime fiction before producing that very accomplished first book? "I'd never even read a crime novel. Not one single crime novel. I read Stephen King, horror stuff. Stephen King was a revelation to me… For the first time I had read books in which dreadful things could happen to people like me."

But she did draw on some professional skills. "The training I did as a journalist [at Cardiff University] was incredibly valuable… right from when you were a trainee your copy was going straight to the newsdesk of every national paper." She worked as a journalist for an agency, and as a screenwriter. "If there was something wrong and they didn't like it they would come back to you and give you such a bollocking – you have to be completely ruthless to yourself."

Bauer loves Cardiff and stayed on in the city after she completed her course, but that's not the only reason why her fourth book, Rubbernecker (Bantam, £14.99), is set in her adopted town. "I felt that Shipcott had run its course. Also I did a talk for a Writers' Guild meeting about two years ago and it was quite a hostile crowd… This old chap actually stood up and said, 'If your book, Blacklands, had been set in Wales it wouldn't have had half the attention it's had'… I thought at that moment 'I'm going to set my next book in Cardiff, whether it fails or succeeds, just to prove this bloke wrong'." Luckily, "the idea I came up with was perfect for being set in Cardiff – it had the University here, the dissection room I needed."

Ah, yes, the dissection room, so graphically described in Rubbernecker, where her leading character, Patrick, is an anatomy student. Did she see one? "Yes, I did. I went into the dissection room and was very nervous because I was so squeamish. I spent a lot of time there… just getting an idea of exactly how everything works… I'm really glad I went because the smell of the place was bizarre and unforgettable." In the book, she describes that smell precisely: "dead flowers over shit".

This brings us on to Patrick, who suffers from Asperger's syndrome and regards life with the sort of clear-eyed logic that makes it difficult to understand other people's feelings. Determined to study anatomy, he takes his place in a roomful of dead bodies and mostly nervous live students. He is unfazed, and hacks and saws his way through Body No 19 in such graphic detail that any of the current Cadaver Queens of crime fiction would be put to shame.

Patrick has a sad history: his father has died in an accident and his mother, Sarah, is so distressed by his behaviour that she is driven to wish she had never given birth to him. Yet Bauer recognises something of Patrick in herself. When I asked her who she would identify with most in the book, she immediately answers, "Patrick absolutely, because of that slight disconnection with people… in my first three books I had a very sensitive male hero and as a challenge to myself I decided to see if I could write a protagonist who actually had no empathy really for anybody else."

So was Patrick a process Bauer had to work through? "My books are really not crime novels. They are about characters dealing with something in their lives – a man trying to come to terms with the terminal illness of his wife, Patrick trying to find out what happened to his father. The personal relationship he has with his mother, his only surviving parent, is critical, because she's all he's got and the relationship between them pivots on the father… My father died about three years ago and I've learned more about him as a person in those three years than I ever knew about him when he was alive."

Her combination of powerful imagination with a certain detachment seems to have been present at an early stage; as a child she loved solitude. "I had lots of friends but I didn't want them to come round to my house and play with me… I would lock myself in my bedroom. I had three sisters and I wouldn't let them into my room to play unless they paid me for half an hour. After half an hour I used to kick them out… I was having a much better time in my own head than I could possibly have had with anybody else . It was only when I started to write Rubbernecker that I realised this about myself, that I had a great affinity with Patrick, and by the end of the book I was really envious of him - every time he said exactly what he wanted to say, without fear of hurting someone's feelings or being misunderstood."

There was another plus to having Patrick in the book. "Somebody with Asperger's dovetailed perfectly into the plot – it was just the right thing for him to have to do, solve a murder mystery without interrelating with other people or understanding the nuances of communication."

I asked Bauer if she agrees with Graham Greene that an author must have a certain detachment, "a splinter of ice in the heart"? "Yes, I think that's really true. You have to be completely detached from any empathy or sympathy… and put down in black and white what a paedophile might feel – that splinter of ice comes in very handy. I'm lucky enough to have that complete objectivity. Although in my day-to-day life I'm very sympathetic, very easily moved to tears."

Bauer's eyes actually fill as she tells me about a woman she met at the vet's who had to have a much-loved dog put down. Her immediate warm reaction was to give her a big hug. She clearly has an intense capacity to empathise that coexists with authorial objectivity. Her own favourite work is Harper Lee's To Kill a Mocking-Bird, which she says is "the best book in the world". Because Atticus - the lawyer defending the innocent accused man - has such a burning sense of justice, I suggest? "I share it, and I think it's what readers want." But Bauer has a final chilling insight into the popularity of crime fiction. "Statistically all of us know a paedophile, statistically all of us know a rapist. Most people try to go through life not thinking about it. Maybe that's why crime writing is so popular – it exposes those things and we can close the book and have a little shiver and think, 'Well, it's not happened to me – yet.'" That nerve-racking "yet"! It's authentic Bauer gold.