It had taken us a day of climbing to reach the valley. The locals called it Dyffryn Sibrwd - the Whispering Valley. According to them, it was haunted by the bwbach.

"Mist spirits?" Jonas laughed when he heard this. "No such things! Those are just stories."

The old men at the end of the bar glared at us. "They're not stories, mind," one of them began. "They're real."

"The only spirits I believe in are these," Jonas replied, and held up his glass. "Another double please, landlord."

So, the next morning we set off up the mountain trail, slightly the worse for wear. It did not take long for our hangovers to disappear, washed away by the cold Welsh air and the spring sunshine. We climbed high into the mountains, until we could see the blue-grey waters of the Irish Sea on the horizon. Then we angled our path towards the gap between two peaks, and started our descent into the Whispering Valley.

While the mountainside had been bare and rugged, covered only in hardy grasses and low shrubs, the valley was full of trees. The still air was heavy with the scents of bark and sap. There was birdsong everywhere. It was a relief to come down from the ridge and into the shelter of the wood. It didn't take us long to find a campsite. We set to, clearing away the leaves and rocks, and pitched our tents in a circle. Then we set a small fire, and the smell of smoke from the blazing branches mingled with the aroma of cooking. After we had eaten, we talked and watched the sky above us turn dark. Then we said our goodnights and headed for our sleeping bags.

I was woken by the sound of whispering voice: indistinct words muffled by the walls of my tent. I lay in my sleeping bag, my mind trying to make sense of the muttering. The sound of the voices rose and fell with the cadence of speech. I sat up. "Hello?" I asked.

There was no response; the whispering continued unabated.

"Could you keep it down? Some of us are trying to sleep." I tried to put some feeling into my voice - hopefully enough to make sure whoever was outside would know I was annoyed - but keeping quiet enough so that I would not wake the others.

The whispering seemed to grow louder, more insistent.

I fumbled in the dark for my shirt and pulled it over my head. Then I crawled to the end of the tent and undid the zip. It took my eyes a moment to adjust to the pale moonlight so I could see the silhouettes of the other tents. I struggled out into the open air and listened carefully, trying to work out which of my companions had woken me. However, the voices I could hear were not coming from any of the tents. Instead, they seemed to be coming from the trees.

"Hello?" I took a step forward, out of the circle of tents. "Who's there?"

The voices stopped.

"I know you're out there. You can stop it. Now."

I heard a peal of laughter from somewhere among the trees. For some reason, it made me feel angry - foolish. I wanted to find whoever had woken me and let them know what I thought of them. I picked up a fallen branch and followed the laughter. The voices started again. This time they had a mocking tone to them. I raised my makeshift club and shouted, "Right! Enough!"

Something hit me on the arm - something small and sharp! I yelped in pain and turned to face the direction I thought it had come from. "What the - !"

I felt another sharp pain as something hit me in the back. Instinctively I spun around, hoping to see something in the darkness. More missiles came out of the tree, peppering me. Each shower of shot was followed by more laughter, more mocking words. I started to run, trying to find my way back to the campsite, back to safety, but I had lost my bearings. I ran through the trees, herded this way and that by my unseen assailants until - !

I woke, cold and stiff. The sky above me was grey with the pre-dawn light. I must have spent the whole night lying on the ground. There was a lump the size of an egg on my forehead, and I could see small blisters on my hands and arms. Slowly I got to my feet.

The morning breeze brought the scent of fresh woodsmoke. At least now I knew which way the camp was. I followed the breeze until it brought me to our tents. Jonas was sitting by a newly-lit fire, sipping from a mug of tea. He raised his mug in salute. "Hey. Where have you been?" He looked closely at me. "Are you alright?"

For a moment I thought about telling him what I remembered of last night's events: of the whispering in the darkness, of the trees, of my unseen attackers. I knew that he would not believe me. "I'm fine," I said. "I got up for a pee, but I slipped on my way back. Hit my head."

Jonas gave me a strange look. "Are you sure?"

I nodded. "Yes. But I could do with a cup of tea."