But it’s pointless; Liam’s determined to find the person and confront them. I’d do anything to avoid conflict and never used to assume that people had nefarious intentions, but Liam’s the opposite. He’s like a dog with a bone when he goes after something, and he always assumes the worst in people and situations: another symptom of his police work.

When we reach the castle, I notice just how impenetrable the stone walls are; though weathered and pocked, each slab is at least a foot and a half thick, and there are two towers still left standing among the ruins. I stare up at the pointed arches and buttresses. It reminds me a little of pictures that I’ve seen of the Notre Dame cathedral in Paris: several leering gargoyles carved into the stonework above the door stick their tongues out at us. It’s ugly and imposing, even more so in its decay, and I really want to turn tail and run.

The downstairs windows are all solidly boarded up, with no way of gaining entry unless we had a sledgehammer or a saw, but Liam walks around the entire circumference of the building, looking to see if any boards have been pried loose, and I follow a few steps behind. When we reach the front doors, we see that they’ve been covered with two heavy steel panels, the bolts drilled into the stonework on either side. I feel quite relieved that we won’t be going inside.

I stand on the scarred stone steps leading up to the entrance, my mind flashing back to the photograph in the book. I’m standing in the exact place where the McKay family stood. I remember the look on Nancy’s face, her hand resting on her son Elliot’s shoulder, and I shudder as if someone just walked over my grave.

I look around then and notice that Liam has vanished. Panicked, I run around the corner but there’s still no sign of him. ‘Liam?’ I call out, suddenly afraid.

There’s no answer. I shout his name again.

‘Over here!’ I hear him yell back, and then I spot his head emerge from what looks like a hole. As I get closer, I realise he’s actually just down some steep stone steps that lead to what was probably once a servants’ entrance or maybe even a coal scullery door, judging by the small size of it.

‘It’s been forced open,’ Liam says, pointing at the boarded-up doorway. ‘Look.’ He yanks on the plywood covering the entrance and it comes away easily. It was merely there as a prop cover. Liam pulls out his phone and turns the torch on. He shines it into the dark, cave-like interior, then takes a step inside.

I hesitate. ‘I don’t know if this a good idea,’ I say.