‘Maybe we should write a joint paper about the role of cats and genes and scans and psychotherapy in the diagnosis and treatment of schizophrenia,’ said Martin. ‘I could write up some case studies and you could look into the genetics and neuroimaging.’

‘Hang on,’ said Olivia. ‘I’m on holiday. Anyway, I’m not qualified to make the neuroimaging case. You could ask Ash, Lucy’s friend; he’s a neuroscientist as well as a medical doctor.’

‘Excellent,’ said Martin. ‘A project! Schizophrenics are a hundred times more likely to kill themselves than ordinary people. If genes were the culprits, why has the scythe of natural selection not eliminated something so disabling?’

‘Well, the true believers have an answer for that: the reason why there are so many feeble and widely dispersed correlations is that the big culprits have been eliminated by our hero Natural Selection.’

‘So, in that story,’ said Martin, ‘schizophrenia used to be a much more genetic disease than it is now, but although it’s becoming more common, it remains genetic – amazing, truly amazing.’

Although Olivia had parted from her father protesting that she wouldn’t take on a project just yet, she was in fact tempted by the idea of working collaboratively after the long haul of writing alone. She thought about where she might start from. There was only a short passage mentioning schizophrenia in her book, but it showed that there were one hundred and twenty-eight genes in one hundred and eight loci associated with ‘enduring psychosis’, and most of the variants were also associated with bipolar disorder, attention deficit and autism. In the extreme case of 22q11.2 deletion syndrome there were one hundred and eighty clinical associations, of which schizophrenia was only one. When this immense scattering of tiny, ambiguous effects was swept together, the resulting pile of dust still only amounted to a meagre genetic difference between schizophrenia patients and control groups. Nevertheless, she wasn’t going to commit to a joint paper today, despite her father’s enthusiasm.

As she was going to see Lucy in the flat that Hunter had lent her, Olivia made only token preparations for going out. What she needed above all was a strong cup of coffee to ward off the listlessness and creeping headache and faint despair that seized control of her decaffeinated body after four or five hours. Perhaps she should have a scheduled withdrawal in Willow Cottage, with Francis bringing her black and then green and then white tea, while she thrashed and sweated and mumbled, strapped to the bed in a locked room.