‘It must feel like drowning in the air,’ I said. I wouldn’t wish my dreams of choking on anyone, and I’d been unconscious for most of my time in my mother’s car as a child. I’d read of divers drowning within inches of the surface, feeling if they could just break through the water they’d be saved, but it being just, just, out of reach. I couldn’t imagine trying to breathe the air in front of you and getting nothing from it. ‘If you think it’s the same killer, you think it’s the same equipment, right? It’s not just the ash that got you thinking. You think the mark on his neck could be made from a zip-tie?’

‘I do. It’s cut into the flesh cleanly enough to be something plastic, rather than rope, which would tear the skin a bit, and if it was fishing wire, it would be a deeper cut. But here, look . . .’ She pointed at the corpse’s mouth, which was slightly open, took out her phone (battery: 85%) and shone the flashlight in. It was no mystery why the media had dubbed the killer the Black Tongue; the dead man’s mouth was caked with black charcoal, making his tongue a thick black slug behind his smeared teeth. ‘It’s more ornamental, rather than the cause of death. The bag would have done the job of suffocation anyway. This serves no purpose other than to leave a mark.’

‘Why would he do that?’ Erin asked.

‘I’ve seen my share of weird shit in the ER, so I can guess at a few reasons. You know what I’m thinking Ern, I’ll bet. You write this stuff. What’s the basic principle of a psycho killer’s MO?’

‘Well,’ I said. ‘I suppose the most common assumption is that psychopaths just need to do things a certain way. It’s a part of their process – it means something to them. But if it were that important, I don’t think they’d put the effort into killing without all their affectations in order, unless they were interrupted. It wouldn’t be worth it. And it’s not like someone’s building bonfires up here. That would be pretty obvious. So I don’t know how that helps.’

‘You don’t need fire as much as you might think, actually – the trick is just to get those particles in the air. And you can buy ash in big bags from any garden or hardware store. My point is, they probably brought it with them. They were prepared. So my second theory is, I think, more likely.’