Grant smiled as Shelley stopped the car on the shoulder of the highway. "Is this a joke?"

Shelley smiled back, shaking her head. "No joke. This is the place."

The place was expansive and empty. Five pm on a Wednesday afternoon, middle of the Karoo. Not a soul in sight, nor a town, nor a structure, just flat scrub-brush and sand everywhere you looked.

"You're going to leave me here?" Grant asked, maintaining the smile on the outside only.

"Do you want to see Sowan?"

A minute later he was watching the little Corsa trundle away from him into the emptiness. He wanted to pretend, even to himself, that he could deal with this, but it felt as if his bones were shrieking silently. Just stay standing upright till she can't see you any more, he thought.

It was a long, long way to the horizon, and sunlight still glinted off the tiny speck of the car in the distance when the fear overwhelmed him and he had to sit down.

Grant had been on foot in the Karoo before, many times. Much of his military career had been spent out here, in the dark old days of Apartheid, training the country's white young men to hunt and kill. It was not the circumstance of being abandoned in the semi-desert that terrified him. It was the circumstance of being abandoned here on this particular night, October 31, by Shelley.

He had met her one year earlier in a bar in Cape Town. He and some friends had been out carousing after he'd convinced them Halloween was worth celebrating. Few people in South Africa noticed the holiday, or cared, but Grant had been brought up to respect it by his Irish grandfather, who had called it Sowan. Every October 31st of his childhood, until the old man died when Grant was twelve, the two of them had built a bonfire, bobbed for apples, and swapped stories until after midnight. Daddo's stories were always much better than his, filled with strange-sounding words made exhilarating by the fact that when written they bore no resemblance to their spoken forms. Sowan, he learned, was spelled Samhain. Daddo was spelled Daide�. His cousins sometimes called their grandfather Shannaher, which they wrote as Seanathair in their letters. It was as if the heart of mystery was encoded into language itself; the mystery of existence and transformation.

In adolescence Grant often tried to arrange Halloween parties for his friends, but there was no tradition in the country and his ideas sparked little interest. Some of his friends celebrated Guy Fawkes, though, and he found comfort in this. It was only five days late, and he could pretend, as he tossed old bones onto the bonfire, that Daddo stood beside him, whispering weird fables in his eldritch tongue.

Adulthood, with its ever-full bottle of disillusionment and disappointment, had seen Grant personalize his celebrations. He never spoke to anyone of Samhain, and Halloween became in his mind just another American thing: horror movies, trick-or-treat, a foreign curiosity. But he celebrated nonetheless. Each Samhain he built a fire and threw bones on it. Each Samhain he remembered the dead, all the dead, especially Daddo. Each Samhain he wept privately at midnight, his tears fuelled both by sorrow and by the beauty of memory.

He accepted, now, that is was destiny that he should meet Shelley. Why else was he out that night? Normally he would have been in the bush, but a catalogue of accidental events led to his meeting up with old acquaintances and bar-hopping, trying to arouse in them some enthusiasm for the holiday. Near midnight, in a little dive off Long Street, he leaned against the bar and, enthused by drink as well as pent-up emotions, shouted "Happy Halloween!"

Seated beside him was a woman whom he had barely noticed before: pale, with tied-back auburn hair and eyes that--when you looked at them--seemed to prod you physically. After his outburst she spoke. "Happy Samhain," she said.

No explanation was ever found for the disappearance of Captain Faran's party. Official documents simply list them as "missing". Local Xhosa were reportedly punished for their death by the confiscation of cattle, but since the whites needed only feeble excuses to confiscate black-owned cattle, this should not be taken as evidence of Xhosa guilt.

It took long for the Karoo day to end. Grant walked through its final hour, into the wilderness as Shelley had instructed. A wind came up first as the sky bruised and then burned. Rocks and bushes solidified and protruded more than before. A jackal howled and then night welled up from between the cracks, like oil. It diffused slowly over everything.

The moon was waxing from new, just a jagged bone among the million shattered bone fragments that were stars. Without knowing why, Grant stopped beside a particular rock and then sat on it. Creatures scuttled and burrowed just out of sight but he was not afraid of them. He became afraid after a few minutes, however, when he realized that the rock on which sat was part of a circle of near-identical rocks, and that he had arrived.

His time with Shelley was something even less comprehensible than romance. An entire adult life without long-term companionship, and then the sudden upheaval of Shelley Faran. He guessed she was about thirty, but she never told him her age or birthday. She hardly told him anything, and he told her everything: he was forty-two, he'd served in the army for fifteen years, his private security company had failed, he was fortunate to have inherited his parents' house, and he supported himself in the neighbourhood with odd jobs. He had a low income but even lower expectations, so it didn't matter.

She moved in with him. At least, she stayed there often enough, but usually brought a bag with her, as if his house was a hotel. She never told him where she was going when she left. She cooked intriguing, delicious food and she sang in Gaelic. She was like a Selkie, he thought; a fairy seal that appeared as a human woman. And, like any fairy creature, she knew magic, which she showed him in the night. Candle, stone, rope, bone, and fire. "You know the word bonfire comes from bone fire, don't you?" He didn't believe her, but when he looked it up it was true. Even in his own language, mysteries were concealed. He wondered where the bones had come from, to fuel such fires.

He told Shelley about Daddo and his youth. She said: "That's why I'm here," and he misunderstood this in different ways for months. She never did anything dangerous, but she frightened him anyway; frightened him even though he was enchanted by her. Once, looking over his shoulder at a book of Celtic fairy tales he was reading, she said, "It's not like that." The picture was of a man bound down by the roots of a tree while gleeful creatures danced around him, bearing torches.

Early in September he said: "We should celebrate Samhain together. Do something really special."

"We will celebrate," she said. "Not together, although I will show you true Samhain."