CAROL Topolski knows her psychopaths. She always has, at least since she left university. She met a few in the decade that she spent as a probation worker and some more might well have figured in the case notes at the rape crisis centre she set up in Canterbury.
In the 12 years she spent as a film censor, she must have seen depictions of further hundreds, their images flitting across the darkened screening rooms of the British Board of Film Classification at Soho Square as she worked out how old you'd have to be to watch them without the experience scarring your mind.
Yet as she talks to me, in her study at the top of her four-storey house in Clapham, about the psychopath protagonist of her latest novel, the threat of dysfunctional violence seems impossibly distant. Quiet, leafy, securely haute bourgeois streets like these, where houses of honeyed London stone sell for at least 1.5 million each, might seem the last places you would look for a lurking psycho.
Then again, anyone gazing down on the street from the top of the house in which Topolski lives in with her lawyer husband of 39 years (a QC for the last ten), should realise that is in precisely where you might expect to find Virginia Denham, the hard-driven obstetrician who is the central character in her gripping psychological thriller Do No Harm. If you saw Virginia returning home after a long day saving lives in surgery, you might pass her by without thinking anything of her. A gangly, lank-haired woman, her fortysomething face devoid of makeup, she would look distinctly unthreatening, carrying nothing more menacing than a bag of gourmet foods from the deli to make a meal for her friend Ruby. But you certainly wouldn't imagine the kind of things they get up to together.
Do No Harm: that is, of course, the first principle of medical ethics: the last thing we expect from our doctors and surgeons is that they should ever knowingly cause harm. Even the idea of a rogue surgeon, of someone deliberately maiming his or her patients, is enough to cause a frisson of fear. Not only does it violate all our tenets of trust, but we have a strong suspicion that such a person could, if they put their mind to it, get clean away with murder. As Conan Doyle once pointed out: "When a doctor does go wrong, he is the first of criminals. He has nerve and he has knowledge."
Yes, but how did he - or in Virginia's case, she - get that way in the first place? That is the real story Topolski has set out to tell in Do No Harm and given her working knowledge of psychopathy, it is one she is particularly well placed to tell.
In her debut novel, the Orange long-listed Monster Love, she sought to show just how far back you have to look in the lives of child-murdering parents, to find the roots of the crime.Calling such people "monsters" is, she says, the quickest way we have of stopping us having to think about that.
"It's what I call nose-job politics. You know, someone says, 'If only I had a nose job, I'd get a great job and have a boyfriend and be happy'. In a similar way, if we call psychopaths and paedophiles 'monsters' and put them in prison and forget about them, it stops us thinking about them and why they did what they did. And with my interest in psychoanalysis, that's precisely what I am interested in."
Topolski was born in 1949 to a mother who was a child psychiatrist and father, Christopher "Kit" Pedler, who later swapped science for science fiction (in 1966 he came up with the Cybermen storylines for Doctor Who). Her own career, which mixes writing dark novels about deviance and working as a psychoanalytic psychotherapist, is a near-perfect synthesis of both of theirs.
"I'm staggeringly undelinquent myself," she admits. "But I've always found it interesting territory to explore. Why? Well, many years ago, when I was training to be a probation officer, I had this supervisor who used to have this disconcerting habit of clearing his ears out with the inside of a Bic pen as he talked to you, and I remember when I asked him the same question, he said, 'Well, you know, Carol, I just like criminals'. And I thought, 'Yes, and so do I', and I wonder why that is. I'm not going to romanticise it and say it's because of their rebelliousness, because delinquency has so many roots, but it's the way they go against the ordinary rubric of what we are taught to do and not to do, because it's so flagrant and bold."
How, I ask, has her own work with psychopaths informed her writing? Surely it must have provided Topolski with some details that add to her own novels' credibility? She sidesteps the question, applying it instead to her work as a film censor. "Some things I saw in the dozen years I did that job are acid-etched into my mind. They were all to do with violence - some paedophile material from film the police had seized, some Japanese sado-masochistic porn - these are extreme images of delinquency I just cannot expunge from my mind."
Yet even though she talks admiringly about Thomas Harris's characterisation of Hannibal Lecter, no one is going to read Do No Harm - as they might do Harris's novels - for its cold-hearted, dexterous violence. Topolski herself reads few crime novels, isn't attracted to the genre, and only concedes with the greatest reluctance that her books should be marketed as crime novels in the first place.
I can understand why. Because what Topolski is offering isn't the shock of the violence but an empathetic attempt to explain it. And for that, her novel spins back not just into Virginia's childhood, but into the fractured relationship of her parents. "Freud always says that when you are working with a patient there are three people in the room, because his or her parents are there too," says Topolski."And I wanted to know something about why Victoria's parents weren't able to love each other, though they were able to find love elsewhere."
So, in a series of scenes marked by a sense of dark foreboding - scenes that put the reader in mind of say, Hilary Mantel in Beyond Black - we find out. In the process, we see a child growing up without love but gradually fascinated by pain. The young Victoria won't understand why that is, only that studying medicine offers her a way of controlling, and even stopping, the pain of others. Such a person could - indeed does - become a great doctor, the kind who lives entirely for her work, whose dedication and commitment is admired throughout the hospital and, as a consultant, amasses an enormous reputation for competency and single-mindedness.
Only we, the readers, know what is being hidden, the depths of her loneliness, the way she forces her body through alternating bouts of binge eating and semi-starvation. Only we know the kind of transgressions, starting with self-harm but ending far more desperately, that Ruby - Victoria's invisible friend - is pushing her towards. And we know too the hidden secrets of the one true friend who is drawn to her, the mother-to-be Gilda, who takes solace in the "vanilla world" of sado-masochism.
Although Topolski remembers once censoring a scene in a documentary on fetish clothing (rubberwear so restrictive that unaided breathing would have been impossible, since you ask), she admits that, before she started her research, this was a world of which she knew next to nothing. "I found out everything about BDSM (Bondage, domination and sado-masochism: keep up, please] from talking to Mistress Absolute, a professional dominatrix in London. She was lovely - bright, forthright and enormously psychologically sensitive. The more I talked to her, the more I realised that at the heart of the contract is trust, and I could see that that beneath all that containing and constraining, what someone like Gilda is looking for is a no-holds-barred, absolute love."
It is typical of the way in which Topolski's novel bursts easy stereotypes of deviancy that Gilda is shown as Victoria's last and best chance of true love. Because that's the thing about psychopaths - they are not completely, single-mindedly evil: they are not caricatures but humans who have, some of them, been offered the chance to change. Some few of them, like Victoria, have also been offered the chance to do good too, and may even, in the course of their life, have done a huge amount of it. "The line dividing good and evil," as Solzhenitsyn points out in the quote with which this book begins, "cuts through the heart of every human being. And who is willing to destroy a piece of his own heart?"
I'd love to find out which elements of Victoria's psychopathy have echoes in the real-life cases Topolski has dealt with, but she is too scrupulous about her own professional ethics to even offer a hint.But just talking to her in her eyrie of a studio, looking out above south London, I sense that she has got closer to the fractured complexity of their inner lives than most novelists - and certainly most crime writers - manage.
What's she working on next? "I'm writing a book that's going to be set in Death Row. Just before Christmas, I spent a month in the south, going into jails in Louisiana and talking to the prisoners on Death Row. Another bloody comedy."
Topolski laughs and looks out of the window. Children are coming out of the primary school over the fence from her back garden, and the sound of their excited laughter floats up into the South London air.
• Do No Harm by Carol Topolski is published on Thursday by Fig Tree, priced 12.99