Frejah Harsent had tested my own understanding of reality. She brought what she claimed was a genuine threat of someone out to kill me. For some reason, she also accused me of knowing too much. That for me was unrealistic, unbelievable. It was she who knew nothing of me. She was a stranger who had power-driven jarringly into my life, created a web of lies, threats, old murders, false names. I still did not know why, and was beginning to realize that perhaps I never would.

In spite of what she said about my being in danger, how could I take any of it seriously?

I went inside the house, made myself some tea. I sipped it while I stood at the window looking out across the garden. I realized only then that for some reason I had closed the garden doors behind me. An instinct to lock myself inside against a possible intruder? I opened them again. Familiar sounds reached me from outside. The thought of some vengeful assassin, out to get me, prowling my island with a tracking device – it was ridiculous even to consider it as a possible threat.

This must be the saving grace of the real world, I thought. In crime novels and movies a murderous threat is taken seriously, at face value. It has an immediate and disruptive impact on the story. The intended victim flees to a place of safety, or rustles up some protection, or sets out on whatever it was that Frejah called pre-emptive self defence – attack being claimed by storytellers everywhere to be the best form of defence.

But fiction is made up. I was not. A feeling of everyday normality spread around me. I lived in a world I had found, not one I had constructed.

If you research the subject of murder and murderers you soon discover that fiction and the real world are entirely at odds. Far from there being some sort of criminal mastermind planning and preparing, fiendishly plotting killing schemes, most murders are impulsive, messy, sordid, and not at all mysterious. They occur as a result of fights and arguments, or most likely of all within a dysfunctional relationship.

Discounting acts of terrorism, more than half of all women murdered are killed by their spouse, their partner, their ex-partner or a work colleague. Roughly a quarter of all murdered men are killed by a friend or an acquaintance or at least by someone they recognize or already know superficially. When children are murdered it is most often, tragically, by a parent, a step-parent or a live-in partner.

In any police investigation of a murder, the starting point of enquiry is invariably within the immediate family, then to the circle of closest friends.

Only a minority of victims are murdered by strangers. Should you take comfort from the thought that if you are murdered the killer is likely to be someone you know?