When I was a child, I lived in Radnorshire. I was one of seven children and the youngest of six girls. As my parents had five other girls and an infant boy to take care of, they left me to myself. I was a wild thing. It wasn't because they didn't love me; they just had other things to do.

I was about five when I began to see the Bwystfel. It roamed about the farm, slipping in the shadows. The only way to see it was to look for the shapes that were darker than the spaces between stars. Its mad eyes were like coal sparks, and it laughed like a goat in pain. It was always angry. I watched it from a distance. One spring, I saw it kill a nest of sparrows, closing its hands around the nest until the little naked birds stuck to its flesh. One summer, it poisoned the sheep, biting the ewes’ legs until rot and infection ate into their flesh and no amount of doctoring could fix it.

Later, it skulked into the shed and sliced the handyman’s chest open, then danced his blood up the walls and over the rafters. My parents said it was an accident, but I knew better. “The Bwystfel did it,” I told my father, and he boxed my ears for being a liar. No one believed me. No one but the Bwystfel itself.

It grew angrier. At night, it crept into my room, giggling and ripping the blankets away and pinching me. I shared a bed with two of my sisters – we didn’t have separate rooms like you do – and when the Bwystfel came, we shivered together, too afraid to move until morning. We were all very little girls, and nobody trusted us with a candle, so we had no way to drive the thing away.

It tormented us in whispers, calling us names and telling us we were bad children because our prayers, that it would leave us be, weren’t answered. My sisters refused to speak a word of it, and they wore the Bwystfel-inflicted bruises like jewelry, saying they’d fallen over or been bitten by the cat.

I decided I would have to find the Bwystfel by myself and scare it away. I took the statuette of Florence Nightingale that my mother gave us to hold when we were sick and a stone with a hole in it, both for luck. As it turned out, I would need the luck.

I walked for ages, got lost, and eventually stumbled into a small copse where I had never been before. The air was cold under the trees. Pine needles and dried leaves lay thick upon the patchy grass. I clutched Florence. That's when I saw the bones.

Bleached and ancient, they lay scattered in a circle: small bones, large bones, bones half-buried in the loam, bones with scraps of dried flesh still clinging to them. A sheep skeleton hung suspended in the tangle of a blackberry bush, and canes had grown through the eye sockets of birds. I started to cry – I knew I’d found the den of the Bwystfel.

The Bwystfel appeared from nowhere, crouched down on the tawny grass like a cat about to pounce. The ivory of the bones jutted up around it like little fingers, clawing, trying to drag it down. “You’d better run, small girl,” the Bwystfel hissed. “Better run, or your brother-boy will break his bones, snap-snap.” It vanished, only to appear again behind me. Terrified, I flung my lucky stone at it; the stone passed right through its head, and the ghoul screamed.

I’d seen enough. I bolted, dropping Florence, and rushed headlong towards where I thought the nearest road would be. Once there, I kept on running. My skirt was ripped to ribbons by thorns, and my legs were stung by nettles. After a series of twists and turns, I ran smack into my grandfather. He was a big man, my grandfather, and he swung me off my feet and held me as I sobbed.

“What’s wrong, darling?” he asked when I calmed down. I told him of the Bwystfel and what it had said, and instead of being angry as my father had been, he listened. His brow furrowed. “Are you feeling brave, darling? Do you think you could be brave for me?” When I nodded, he had me show him where I’d gone – then he sat me on a bank and gave me his best silver snuff box to hold. “I’m going after the Bwystfel,” he told her. “You stay here in the sunshine and I’ll be back soon. If any bad bwcy comes, you hit it with that.”

So I waited, shaking, fearful for my granddaddy, frightened by the Bwystfel, and afraid of what mother would do if I lost Florence. Finally, back grandad came, flushed and bleeding, from a hundred cuts on his hands. He looked angry, more angry than I’d ever seen him, for he was the mildest of men. “The Bwystfel-beast is dead again,” he told me, “and under the soil where it belongs.” He spat on the earth and ground the moisture in with his boot heel.

“What do you mean, dead again?” I asked.

Grandad was quiet for a time, then he said, “The Bwystfel was a damned one who hurt small things because he loved pain. When I was a boy, Old Thomas killed him, but Young Thomas found where he lay and let him out. I’ll sort him out for good soon, and he won’t bother you any more.” When he arrived at my father’s house, he made excuses for my torn dress and tear-stained face, saying I’d been attacked by a dog. He explained that Florence had been broken as I’d tried to escape.

And then, without another word, he went to the shed and fetched the dead handyman’s bottle of whiskey, his gun powder, and a box of matches.

I never went back, but I heard of a fire that burned the bone den trees to the ground.