In Sara Paretsky's fantasies, she was raised as a child by adoring billionaires and showered with love and opportunity. In real life, she was raised in rural Kansas by parents who fought constantly, and put her to work as a drudge in a once-imposing home that sank into squalor.

The painful reality of that unhappy family might surprise Paretsky's millions of fans. In the 1980s, she practically invented the genre of the female detective: her heroine, VI Warshawski, was a feisty private eye much given to designer clothes.

Twelve crime novels later, Paretsky is a worldwide bestseller. But now she has changed direction, revisiting the geography of her troubled childhood for the first time in Bleeding Kansas.

For fans of the orphaned, and rather solitary, Warshawksi, who usually hunts killers against the gritty backdrop of Chicago, Bleeding Kansas might seem alien territory, full of farm families working in sorghum fields, milking sheds and attending church.

In many ways, Warshawski is the personification of Paretsky's escape from rural Kansas for life in the big city. It took nearly 40 years before she felt strong enough to return home on a journey of the imagination.

"Not everything about living in Kansas was difficult, but it was a difficult part of my life. Chicago is where I came of age and became a person, made a reputation for myself, and I didn't really want to go back to that," she says.

Paretsky is 60 now, with large, pale-blue eyes and VI's fondness for fine clothes and cappuccinos. When we meet, she wears a well-cut, tweedy jacket and bright scarf. She admits, with some sadness, that she has given up on the high heels she loved because of age and a bad car accident last year. She is wearing sensible suede boots.

We're in a wood-panelled room hung with heavy curtains in the University of Chicago's faculty club. University life is familiar to Paretsky. Her husband, Courtenay Wright, now long-retired, was a physicist here. Her father was a microbiologist; a native New Yorker who took up a position at the University of Kansas, in the city of Lawrence, when Paretsky was four.

Five years later, the family moved out to the country, to a grand house five miles from Lawrence. It was not due to a hankering for open spaces. The Paretskys, Jewish but not particularly religious, were caught in the middle of what was then still a segregated town. They were white, but still not white enough in a place where the most desirable residential areas were barred to African Americans and Jews.

But at least there were a few other Jewish families in Lawrence and an intellectual life that centred on the university. In rural Kansas where they ended up, and where the Paretskys' closest neighbour was 400m away, the family was completely alien.

All the same, Paretsky has residual affection for Kansas, and fond memories of the two-room school house she attended, and the teachers who told her she was bright and could write. There were five children in the family. Paretsky was closest to her elder brother, Jeremy, who taught her to read when she was four, and she and her next younger brother, Daniel, used to act out dramas.

But much of the time, life at home was hellish. The house itself was well-appointed, with a Tiffany stained glass lamp, silver drinking fountain and imported titles. But neither her father nor her mother knew how to drive when they first moved out to the country, leaving them stranded in a house with their private demons and battles.

Both parents are dead now. Her father, David, a brilliant professor, was respected by his colleagues and beloved by his students, but was a terror at home. Her mother, Mary, was just as fiercely intellectual, but frustrated in her professional ambitions. As a young woman she had been accepted to medical school - a rarity in the 40s - but she was too afraid to take a bus to the first day of class. By the time the Paretskys moved to the country, she had withdrawn to the point that she sometimes hid from her children. She also drank, disguising her alcohol consumption in endless cups of coffee.

Paretsky's childhood was dominated by the misery of her parents' marriage. "They just fought. They just fought about who knows what, about everything. When one of my brothers got a D in calculus, they fought over whose DNA was inferior that they produced a child who could get a D," she says.

Paretsky's function, as the only daughter among their five children, was general household help and care-giver. She cooked, she cleaned, she baked the weekly bread. She looked after the two smaller boys.

Though the Paretskys were a liberal academic family - and took pride in educating her four brothers - she was discouraged from considering a career, or even a life, beyond Kansas. Her parents borrowed money to send her brothers away to college; they refused to do the same for her.

Paretsky suspects they were secretly hoping she would give up her own life to take care of them. She describes them as "black holes of neediness".

They were forever discouraging her from thinking or feeling too deeply. When she was 10, her parents gave her a book about Joan of Arc. "They wanted me to see what happened to girls who were too intense and took the world around them too seriously," she says.

The admonitions seem to have stuck. More than once during our chat she tells herself to "lighten up". "This is why nobody wants to read my books. I'm too intense," she says. It's an odd comment, because it's not true. Her books have sold millions, and a strong part of the appeal has always been the intensely researched back story: the great lakes shipping industry; the war in Afghanistan; the civil rights era.

Looking back, Paretsky does not remember whether she felt lonely. "I think I felt overwhelmed. My mother got drunk. She didn't cope with the house. I was in charge of cleaning the house, looking after the small children, I did the baking every Saturday for my father and my brothers."

She adds: "I think I was just numb for a couple of decades."

Consumed by their own misery, Paretsky's parents had little energy left over for the house. It was gradually buried beneath dust, mould and insect infestation that followed years of neglect. Eventually, the elder Paretskys became too frail for country life and moved into town. They died in Kansas and are buried there. When they sold their house, Paretsky carted away three skips of rubbish from the attic alone.

Away from Kansas, Paretsky thrived. Despite the warnings from her parents about becoming a martyr for her ideals, she has supported political causes for most of her adult life. She is a committed Democrat, horrified by the last eight years of George Bush, the Iraq war and the rise of the religious right.

Her political engagement began almost as soon as she could escape from Kansas. In 1966, the summer of her second year at university, she spent the break doing community service in Chicago. It was the summer Martin Luther King was engaged in the struggle to integrate the city's schools. The violent racist backlash haunts her still. "The violence in the parks that summer around the marchers was unspeakable. It was unbelievable: the signs urging people to fry black people like Hitler had done to the Jews; women coming along with baby buggies that had bricks, or even explosives, in them," she says.

After earning her first degree from Kansas University, Paretsky moved to Chicago to study for her PhD. And there she created her own life and her own version of a family.

She met her husband, a widower with three children, whom she describes as the mainstay of her life. The hero of Bleeding Kansas is modelled on her husband. She did not have children of her own, but she enjoyed helping to raise his boys, and now delights in her grandchildren. And she did not divorce herself from her family in Kansas, despite the scars of childhood. She continued to visit her parents until her father died in 2000. Her beloved elder brother, Jeremy, became a Dominican priest. Another became a vet in

Wisconsin. Only one brother still lives in Kansas, where he is a lawyer.

Early on, Paretsky took a job at a life-insurance company, but by her late 20s, writing was becoming her life. Her first VI book appeared in 1982, and Paretsky has been turning out a new one every two or three years since then.

But only now is Paretsky suffering from writer's block. She is only 25 pages into her next VI book, and it's already a year behind schedule. Confronting the ghosts of her childhood did not banish them; she is still consumed by Kansas. "That book was with me for about seven years and there is nothing else to come to fill its place," she says.

In the meantime, she is rolling over a number of other ideas. Maybe a novel drawing on her husband's work with some of the greatest physicists of the 20th century.

She pulls herself up again for being too serious, says she is usually funnier in interviews. Did that troubled childhood lead her to VI Warshawski and now back home to Kansas? "I wonder about this sometimes. How much dysfunctionality is just enough to make you a writer?" Perhaps, after all, it was the life Paretsky created for herself in Chicago that made her a writer. "Maybe you don't need dysfunctionality. Maybe you need total functionality."

· Bleeding Kansas by Sara Paretsky is published by Hodder & Stoughton at £16.99.