“I am speaking to Commander Adam Dalgliesh in the knowledge that this tape will be passed on to the coroner and anyone else with a legitimate interest in the truth. What I am speaking now is the truth, and I don’t think it will come as a surprise to you. I have known for over twenty-four hours that you were going to arrest me. My plan to burn Sharon at the witch’s stone was my last, desperate attempt to save myself from a trial and life sentence, and all that would involve for those I care about. And if I had been able to kill Sharon I would have been safe, even if you had suspected the truth. Her burning would have looked like the suicide of a neurotic and obsessed murderer, a suicide which I hadn’t arrived in time to prevent. And how could you have charged me with Gradwyn’s murder with any hope of a conviction while Sharon, with her history, was among the suspects?

“Oh yes, I knew. I was there when she was interviewed for a job at the Manor. Flavia Holland was with me, but she early saw that Sharon wouldn’t be suitable for any work with the patients, and left me to decide whether there was a place for her with the domestic staff. And we were desperately short at the time. We needed her. Of course I was curious. A twenty-five-year-old woman with no husband, no lover, no family, apparently no history, no ambition to be more than the lowest in the domestic pecking order? There had to be some explanation. That mixture of irritating desire to please interposed with a silent withdrawal, a sense that she was at home in an institution, that she had been used to being watched, that she was in some way under surveillance. There was only one crime for which all this was appropriate. In the end, I knew because she told me.

“And there was another reason why she had to die. She saw me as I was leaving the Manor after I had killed Rhoda Gradwyn. And now she, who had always had a secret to keep, knew another’s secret. I could sense her triumph, her satisfaction. And she told me what she planned to do at the stones, her final tribute to Mary Keyte, a memorial and a farewell. Why wouldn’t she tell me? We had both killed, bound together by that terrible iconoclastic crime. And then in the end, after I had wound the rope round her neck and poured paraffin over her, I couldn’t strike the match. I realised in that moment what I had become.