I can't say there was anything odd about that day, certainly nothing that might have warned me. It was just a nice summer's day at my Aunt Janet and Uncle Tom's place in Newstead - next to Melrose in the eastern Scottish Borders for those who don't know, which is most people. I'd come down to stay a couple of nights for the wedding, as my cousin Laura had asked me to be one of her bridesmaids. That afternoon a collection of relatives I wasn't that keen on were hanging around the house, being too polite and snaffling all the decent biscuits. So when I found myself alone with my aunt in the kitchen I said I'd take the dog for a walk if she liked.

Aunt Janet's no fool; she looked at me and grinned, and said, "Like that, is it? Well, there's home-made lemonade in the fridge - help yourself to a bottle and take your time."

Soon after, I was walking along the lane with a rucksack over my shoulder and Sandy the dog padding along beside me. He's a Standard Poodle who's almost as tall as a wolfhound and as black as the ace of spades, soft as butter and well trained with it. Good company, for a hot afternoon in the country. We went for a long, long walk around the lanes and down footpaths, until both of us were thirsty and fancied a rest.

I could have turned right and gone down to the river, and if I had then I suppose everything would have been different. In just the next field, though, I could see a nice shady tree, and a cattle-trough where Sandy could have a drink. There were neither cattle nor sheep in that field just then, and the footpath went through, so I reckoned no-one would mind if we stopped for a bit.

As soon as I left the path, I lost what breeze there was as well. It was still and hot, with a smell of wildflowers in the air and a faint tinkle of running water that wasn't the cattle-trough coming from somewhere. Sandy looked around as we went to the trough, head up, ears half-cocked and nose working, then promptly forgot whatever-it-was when he smelt water.

When he'd had his drink, I led him over to the tree and found somewhere to sit down in the shade. It was a hawthorn, the biggest I'd ever seen, and it stood alone amid the long grass and the hum of bees, next to a spring that bubbled up among a duster of huge grey stones. If I'd known then what I know now, I'd have taken one look and run for safer ground - but I didn't. I just saw cool shade, and a nice quiet spot to bit for a while. And Sandy, drat the dog, flopped down out of the sun with nary a hint of trouble.

So in all innocence I sat next to him, and took off my rucksack. Out came the lemonade, and the latest Reunion magazine which I'd had no time to read yet - oh, and a pen and paper, and my trusty old three-volume 'Lord of the Rings' with the pages falling out. I was trying to write an article on hobbits, and that was the only chance I could see myself getting that weekend. But it could wait until I'd read the magazine.

I was halfway through both the lemonade and Reunion when Sandy stirred and sat up, and then let out a sort of half-bark. When I looked up. I saw another dog trotting up to us. It was a white dog that might have been a shaggy greyhound or an uncommonly well-bred lurcher, with a broad green-and-gold fancy collar. Sandy stood up and went hounding over; I grabbed for his leash and missed. Luckily, they seemed to know each other and went into a sniffing session. Still - I scrambled up and went to retrieve Sandy. As I did so, I saw someone who must be the white dog's owner walking up, a young woman - my age at a guess - with long red hair in a braid, wearing jeans and a T-shirt. She smiled and waved, and called out to me.

"You must he one of Janet Crosier's family if you're out with Sandy! Mind if I join you?"

"Not at all," I said politely (and untruthfully). "I'm Beth Curry, by the way."

"I'm Ceridwen Emrys," she said, as the white dog ran back to her. "And this is Drutwyn."

"Welsh?" I asked, getting interested despite myself. Ceridwen nodded.

"Sort of - my family's been up here for a while, though."

I went back to where I'd been sitting, towing a reluctant Sandy, and Ceridwen sat down with Drutwyn on the other side of the spring. She looked over, and an interested expression appeared on her face.

"The Lord of the Rings? Do you like Tolkien, then?" she asked.

"Yes," I said, a touch shy.

Ceridwen grinned. "Snap! I read LOTR ages ago and I love it. I read all of his stuff that I can."

"Even the Silmarillion?" I asked innocently.

Ceridwen laughed. "l've read my way through the 'History of Middle-earth'!" she retorted triumphantly. I couldn't help but laugh as well. So we started talking, and one thing led to another. I lent her my copy of Reunion to look at - she said she'd heard of it but never seen one. She started devouring it at an indecent rate - speed-reader I thought enviously, watching her eyes flick across the pages - so I took the chance to check some references for my article in LOTR.

A few minutes later I heard a polite sort of cough; I started to look up, and the bottom edge of Reunion appeared, hovering above the stones. I reached out and took hold of it. And froze. Literally froze, unable to move, unable to believe what my eyes were telling me. The hand that held Reunion out to me was silver. Metallic, gleaming. Finer than the finest of armour-gauntlets, chased with patterns. Spirals within spirals within glinting spirals ...

This is - not - happening, part of me said. It's not possible! It can't be happening! But it was. Right in front of me.

Celtic art, a corner of my mind decided quite calmly, while I looked at those impossible silver fingers, struck dumb. Like those pieces from Orkney in the museum. Amazing what you can think of, even when the rest of you isn't thinking at all ...

"It's interesting," said a voice.

The hairs on my neck stood up, and my spine crawled. She wasn't human. Not a voice 'unearthly fair', or anything like that - just not human. Not masculine, not feminine, not anything I could interpret at all. Not a human voice, but still a voice born of throat and tongue and lips. Speaking perfectly good English, in that unplaceable accent. And I was afraid for no reason and every reason, glued to the spot in tongue-tied shock and petrifaction, mouth gone dry and heart hammering. While Sandy just sat there and wagged his tail, blast his curly hide.

"Interesting," Ceridwen - if that was her name - repeated, letting go of the magazine. "You would do well to remember certain things, though." There was a tiny pause.

I meant to say "What are they?" but all that came out was "Nngh?"

Ceridwen - it - her - thing - oh god, whoever! - shifted slightly, with a rustle and an odd jingle.

"Firstly, Beth, you must remember that Professor Tolkien based his Middle-earth on this world - your world. What else is middangeards, after all, but this middle country as your forefathers saw it, poised between their Underworld and Otherworld?

"Why think you he was willing to set the deepest roots of his Silmarillion tales aside, though it were the work of a lifetime and nearest his heart of all that he wrote, in order to make his tales fit with what your scientists think true, unless this middangeard were Middle- earth in truth? Beyond that, the world that Tolkien wrought is tied fair and square to the when of its writing and the when of the peoples and places upon which he based his inventions.

"The limits of his vision were wider than the limits of his knowledge, but the one set a border upon the other, as they do for all kinds beneath the sky of stars who have imagination. It was a wise man indeed who said that the Universe was not only queerer than your sort imagined, but queerer than you could imagine. I suppose there might be something like Middle-earth somewhere in the Forty Isles, but if there is then it's surely nowhere near here, for I have never heard tell of it."

Was that a hint of amusement, in the not-human voice? I couldn't be sure ... There was a sound of someone getting to their feet.

I looked up - and promptly wished I hadn't. She was ageless, inhuman, unreadable. She? Maybe, you couldn't have told by her face whether this was male or female. Humanoid, but not human ... I started to shiver. Fierce-looking, you might say, but who knew what that hawk's set of features meant to their owner - or her kind?

She still had red hair, yes, but nothing human ever went crowned with that mix of copper and flame. And she wore not T-shirt and jeans, but tunic and trousers. Green, naturally. No wonder Auntie Janet won't wear it! slithered through my mind. There was a long gold-hilted sword at her side, on a belt with a golden buckle that made the one from Sutton Hoo look like trashy costume jewellery. And the dog, a tall slender white sighthound with red ears and brilliant blue eyes like a cat, standing at her heel ...

Worst of all, behind her everything was shifting and wavering. As if the field, the hedge, the Eildon Hills themselves were all just painted on a gauze curtain, blowing on the slow hot air ... and if you looked just right, you could see things through the curtain. See somewhere else ... Sitting down or not, it was like looking over the tallest cliff there ever was. And I can't stand heights. I dropped Reunion, clawing at the earth to keep my balance.

"What's the other thing?" I asked, mouth on autopilot - I still don't believe I did it. And she laughed. Or that was what it sounded like, at any rate. Laughed, while I sat there staring and shivering. I didn't know what I'd done, how she'd react - I couldn't read or predict her at all. Not-us, not-human, wild, Other. And that really gave me the habdabs - screaming ones, if I could have moved or made a sound.

"The other thing?" Ceridwen said at last. "Beth, Tolkien was a very learned man, and withal one who saw further and deeper than most among your kind. Much he knew that was not be found shut within the covers of hooks. Yet he was also a great writer who was telling stories, and to that purpose was shaped all that he said. From among the many threads of his knowing, Tolkien chose only those with which he might make a thing true to his own vision, and all that he touched he changed, as is the poet's privilege.

"If you would deal with such as I, seek true knowledge and set not over-much faith in one man's tapestry of words. All tellers weave their own tales and all tales, new or old, wear a mask of deceit, though their heart may be true. Or may be false, for that matter, for many tales are told that are but the work of blind fools, fact alike with fiction - and some will lead you to a cliff's edge. Choose your path and your guides with care, and be not afraid to turn back, even as if you wandered in the hills.

"Take Sandy and go home now, while you may. And, Beth - while you are at the farm, it would please me if you would tell your aunt Janet that one who is known as Ceridwen Tôn Velyn, yn LIaw Eraint, was asking after her."

And she went. How, or where to, I don't know and don't want to. Ever.

I can't remember putting things back into the rucksack, but I must have. For certain, as soon as everything stopped wavering, I was on my feet and grabbing for Sandy's leash, and running as if fire was at my heels. I don't think I stopped until we were back at the farm, and it must have been well over a mile. Luckily for me, I arrived into a real kefuffle.

The cake and the bride's dress had just arrived, and Uncle Tom and Uncle George were in the middle of a furious argument about something to do with sheep and Brussels. No-one noticed I was in a state of gibbering hysterics - or that I promptly locked myself in the upstairs loo and didn't come out for half an hour.

I couldn't honestly tell you what happened that evening, or at the wedding the following afternoon. Everything went by in a sort of daze. It wasn't until the dance after the reception was going with a swing and I was three sheets to the wind that I finally plucked up the courage to say to Aunt Janet that I'd met an acquaintance of hers while I was out walking the dog.

"Oh, who was that?" my aunt asked.

So I told her. And she told me a thing or two, to put it politely. I never would have guessed Auntie Janet knew that many swear-words if I hadn't herd her use them. We've talked, since then, and I've learned a lot from my aunt. Enough to be far more careful about hawthorn bushes, at least. Not to mention other things.