‘He said to give you this.’ Isla reached into her trouser pocket and pulled out a piece of folded paper. I opened it up to find an elaborate and highly abstract sketch, a diagram of sorts. Lots of lines and arrows and circles, like a zodiac.

‘What is it?’ I said, turning the page to the side. There was no indication which way the sketch was meant to be viewed.

‘It’s the mural,’ Isla said flatly. ‘The thing you’re painting inside the Longing.’

I stared at her, wondering if I’d misheard. ‘This? This is the mural?’

She cocked her head. ‘Is something the matter?’

‘No, no …’ I said, though I didn’t sound convincing, even to my own ears. ‘I suppose I thought there might be more to it than this. Written instructions, perhaps.’

‘That’s all Mr Roberts has given me. He said I’m to fetch whatever equipment you need to do the job. So perhaps you can write me a list of whatever you’ll require and I’ll get on to it in the morning.’

Still dumbfounded by the sketch, I said I would, but that I’d need to see inside the Longing first.

‘Ah, now that would be an idea,’ she said, straightening a lampshade. ‘How about I show you just now?’

Outside, harsh winds buffeted us on the rocks, and I saw movement on the far reaches of the island. Seals, Isla told us. I was astonished at how close they were to the bothy, but she told me they were shy creatures, despite their size. They’d not bother us. I watched them slip off the stones into the black water, their shape in the dark almost human.

The lighthouse stood twenty feet away from the bothy towards the far end of the cliff. We all pushed against the wind towards the heavy metal door at the base. I could make out an object wrapped around the handle. A tree branch. I made to pull it off, thinking it had been blown on there by the wind and become stuck. Isla stopped me.

‘Rowan wood,’ she said. ‘It’s for protection.’

I had no idea what she meant, but I stepped back as she tried to leverage the door open. Finally, it shifted. I lifted Clover on to my hip and held Luna’s hand tight as we followed Isla inside.

‘Bloody hell,’ Saffy said, looking around. ‘This place is rank.’ I shushed her, but couldn’t help agreeing internally.