My fumbling hand found a light switch on the wall just inside. I flicked it, and to my relief a yellow electric light came on. It was weak, and flashed on and off a bit, but it was better than trying to use our phone torches on the stairs. As someone who’d always lived in a London flat, the idea of having a basement at all was already pretty weird to me. There was a damp smell that seemed to have soaked into the stones themselves as we descended.

I found another light switch at the bottom of the staircase and flicked it on, my whole body braced for … I don’t even know what. But when the light filled the room we saw that it was empty except for an old backup generator. The fact that there were no windows made it seem cramped and claustrophobic, 255but that was all there was to it. It was just a room.

“Perhaps Charlie was making it up,” I said. “It’s not even underneath the kitchen, is it? The stairs led straight down, so this room must sit beneath the entrance hall.”

We poked into the dusty corners a little more, but it really didn’t seem as if there was anything here to find. No writing on the walls, nothing. I couldn’t work out whether I was disappointed or relieved as we made our way back upstairs. I checked to make sure Dad and Kate weren’t around, then Will and I quickly returned to the tower.

“Look, these are the letters I told you about.” I pulled out the ones I’d taken from Charlie’s walls earlier, and Will and I read them together. They were similar to the one I’d read before – nightmare accounts of birds that had become dangerous. The boy was clearly terrified of them.

“Let’s take another look at the Strangers’ Room,” I said.

One way or another, it was the focal point to all this. Kenzie had spent her final moments there, and it was the last place I knew Rosie had gone too. My eyes went to the window as soon as we walked in, and 256I saw that there was an object on the window ledge. It was the little tin soldier Charlie had been playing with before, staring straight out through the glass, as if contemplating the grisly instruction painted on the wall. Had Charlie been up here again? I slipped the toy into my pocket before turning my attention to the rest of the room.

When I took a closer look at the horrible graffiti encouraging people to jump, I noticed for the first time that someone had dug gouges into the panels too, in the form of words:

Now that we looked more closely, several of the panels had been carved with this message. They were faint, and clearly old, and you had to look hard to spot them, but they were there.