There was no response, nothing. Awful images filled my head of Rosie falling from a cliff edge into the dark sea. I tried to control my rising panic and think. My sister wasn’t stupid – she wouldn’t have gone wandering off in the fog, no matter how upset she was. Yet I was certain she was no longer inside the lighthouse either. Something had happened to her. I knew it.

My T-shirt was damp with sweat, and I was gasping, struggling to breathe in the fog. I couldn’t just go back inside and wait for the weather to clear. I had to find Rosie. So I set off away from 164the lighthouse. Surely if I went very slowly, carefully feeling my way and not straying from the path, then it would be all right.

I knew Dad would forbid it, so I didn’t bother to go and find him first. I just left, inching my way along, calling out Rosie’s name. By the light of my torch, I could see the tiny bit of path directly in front of me, but that was all. The fog felt like cold fingers stroking my skin, and I shivered. The taste of the sea had never been so strong on my lips, and it was no longer only salt but also seaweed, spiny fish and the skeletal ribs of forgotten underwater wrecks.

A gannet was startled into sudden flight somewhere to my right, and I yelped at the sound of beating wings. I felt the sleek softness of feathers brush against my face. But I still couldn’t see anything except for the area directly in front of me. A chilly breeze tugged at my clothes and I felt as if it wanted to drag me right over the edge of the cliff.

I continued to inch my way along the path when suddenly, out of nowhere, I heard humming – a woman’s voice, ghostly and sorrowful. I stopped in shock, but then the sound melted away and it didn’t feel real. The hairs on my arms stood up, and I told 165myself it must have been the echo of the waves crashing in the unseen caves below.

Time seemed to unravel in the fog and it was hard to tell how long I’d been out there. Was it five minutes or an hour? Maybe this was a dream? Maybe I’d wake up any minute now, tucked up beside Rosie in our sleeping bags… But the fog was too cold and wet on my skin, and I knew I was awake, that this was really happening. I carried on searching and yelling Rosie’s name until I was hoarse.