‘Yes, I’m sure they do. But I’m someone else’s loved one left behind – well, barely tolerated one, anyway – so my fears are elsewhere. You know what?’ I laugh. ‘This Billy stuff, for me … it’s a welcome distraction. Not that I want him to shoot me dead, but if I get to avoid what my grandmother went through, if I get to avoid spending any more time on a cancer ward, that’s quite a big consolation.’

‘Let’s go back to your no-best-friend claim. You’re sure there’s no one?’

I take a deep breath. If he doesn’t already think I’m crazy …

‘There’s no one. But …’

But the little white book on Ward 10’s noticeboard didn’t come from nowhere, for no reason. It wasn’t intended for nobody.

‘Billy might think there’s someone,’ I say.

As embarrassing experiences go, trying to explain to a police detective about your imaginary friend is up there with the best of them. Briefly, I’d entertained an idle fantasy about befriending the woman I’d met outside the hospital while Marion was dying: Faith Kendell. Her misanthropic world view had impressed me. I felt obliged to divulge to DC Gibbs that words on the subject of friendship had passed between us.

Friends are too much work – like houseplants.

I agree. Also like houseplants, they all die in the end. What’s the point?

If only someone would say to me, ‘I’ll be your friend, and I’ll expect no more from you than a dead houseplant.’

I’d say that to a prospective friend.

You would?

Yep. Wouldn’t be able to put in much more effort than a dead houseplant myself, so I’d accept being treated like one as a fair deal.

Mutual dead houseplant friendship – it’s an interesting concept. Unconditional acceptance of no effort on both sides.

Sounds like the way forward to me.

Could Billy have been listening? Even if he had been, it made no sense. He’d given me my white book nearly a year earlier, when he’d had no way of knowing that on 6 January 2015, I’d be at the RGI visiting my dying grandmother. So what was he doing there that day, with a white book containing a line from the same poem? He had no reason to believe I’d meet a woman outside the hospital whom I’d briefly consider befriending, before rejecting the idea. In any case, the ‘Death devours’ white book was pinned to the ward’s noticeboard before Faith and I had exchanged a single word. Try to put it together and it makes no sense. So why can’t I shake it from my mind?