It didn't make sense, I know, but I was fascinated by this woman. I kept replaying our conversation in the restaurant over and over in my head. I found I had even started inventing fresh conversations, trying to guess what she might say, which was, of course a fairly futile pastime because I couldn't fathom her at all, and trying to imagine how she might react to situations. I was, therefore, rather disappointed when she didn't reappear. She had had two rucksacks with her: was she a traveller, wandering around Britain on a shoestring budget and cadging meals off gullible strangers, in which case I would never see her again? Had she found my company so boring she didn't want to repeat it and had found someone more interesting? That was crazy! I was getting jealous that this woman, whom I only knew as "Fetishdoll", and with whom I had done nothing more intimate than share a single Indian meal, was having a better time with someone else than she had with me. Finally, I began to doubt whether the whole thing had happened at all: had I imagined the entire scenario? It wasn't out of the question, because it had been a surreal evening from start to finish.

After about a month, I had more or less forgotten Fetishdoll, and no longer looked for her at the railway station, or as I passed the Indian restaurant. It was almost inevitable, I suppose, that this contrary woman would choose then to reappear.

It was a swelteringly hot day, unpleasantly humid and sticky. I was in a very bad mood, hot and uncomfortable after an hour on a packed, stultifyingly hot train, and with a headache starting which I knew before long would feel like someone was drilling through my eye sockets without the use of anaesthetic. I had laddered my tights, the waiter on the train had spilled coffee on my skirt and the handle of my briefcase had just disintegrated. It was not a good end to the day. I needed cheering up, I decided, and did what I usually do in those circumstances: went shopping.

It was late night shopping and the centre was still busy as I made my way to my favourite boutique, picking my way through fraught mothers with tearful children, hard faced women with stoical husbands and sullen teenagers with attitude. The fashion world seemed to be in a Van Gogh period, with virtually every garment either gold, honey, buttercup or some intermediate shade. Unfortunately, yellow makes me look pasty faced and undernourished, so I was going to have to look unfashionable this season, and stick to my usual darker colours.

Since the waiter had messed up my skirt by spilling coffee on it I decided to replace that, and began to peruse the racks. I found a couple of likely specimens, a very short black number which could double as a work outfit and a nifty social piece, and a longer, dark brown skirt which would be a perfect match for a blouse I had bought the week before. Snatching them up, I headed for the changing rooms to try them on.

In my cubicle I slipped out of my skirt and tried the long, brown one. It was okay, quite tight fitting and reaching down almost to my calves. I wouldn't want to walk far in it, but it looked good, making me look fit and lean and, although this may just be wishful thinking, a little taller. I turned around, checking myself from every angle in the mirrors attached to all three walls of my cubicle. Yes, a nice shapely bum, rounded but not too large: this skirt was mine. I unzipped and stepped out of it and put it back on the hanger to take to the counter. Bending over, I reached for the short, black skirt to try it on.

"Hey, nice ass,"

I froze for a second, not sure if I had really heard correctly. Looking up, I saw reflected in the mirror in front of me the grinning face of Fetishdoll peering at me through the curtains.

"Have you tried on that yucky brown one yet? It isn't you, love, don't buy it. The black one, though, is definitely for you."

She was doing it again. This woman had the facility to amaze, irritate, embarrass and fascinate me, all at the same time. I'd never known anything like it. I stood staring at her in the mirror, unable to articulate anything resembling a grammatical English sentence and acutely aware that I was wearing regulation, workday white panties which were about as seductive as garlic breath in an elevator. Unsurprisingly, Fetishdoll seemed to guess my discomfort.

"Hell, Harriet, who bought you those? Your grandmom?"

As I gaped at her, mouth impersonating a fish with lockjaw, she eased open the curtains and stepped inside the cubicle with me. Contemptuously she picked up the brown skirt and threw it to the floor; with a flourish she held the short, black one aloft and repeated that this was the one for me. She took it from the hanger, unbuttoned and unzipped it and held it for me, beckoning me to step into it. I did so and she gently drew it up past my ankles and calves, over my knees and on towards my thighs. She was to my left and slightly behind me, and I could feel her breath on the back of my thigh as she continued to pull it upwards, struggling to ease it over my hips. Heaven knows what would happen if we were found, two women together in a shop changing room, but having her so close to me as she fitted the skirt around me was very exciting. Too exciting, to be honest, since I was aware that I was getting aroused and could feel the familiar stirrings from my pussy. I didn't want to start getting too worked up: it was bad enough being discovered in "grandmom's underwear" but it would be infinitely worse to be discovered getting them damp through sexual arousal.

Fetishdoll pulled the skirt up to its full extent and, tucking my blouse inside it, zipped and buttoned it. She took a step backwards, looking for all the world like an artist retreating from her easel to examine her work.

"Now that is what I call sexy," she said. "Turn around." I did a pirouette, looking at myself in the mirrors. I have to admit, I did look good in it. The skirt was a couple of inches above my knee, tight but not bursting at the seams, and showed off my bum and legs pretty well.

"Hey, that really is some ass you've got, girl," said Fetishdoll. She seemed to have an uncanny knack of reading my thoughts. "This is the one for you. It really shows you off." With that, she idly stroked her hand up and down my thigh and bum, as though trying to gauge its roundedness. The effect was electrifying: there was no denying it, I found her presence exhilarating.

"Yeah, it's okay," I said in a husky voice.

"We need to get you some decent underwear, though. Come on." With that, she slapped me hard on the bum and started to unzip me again. As she did so she knelt in front of me, sliding the skirt back over my hips and thighs. She was right next to me, eyes in line with my panties, and couldn't help but see the little damp patch forming on them. Her face broke into an enormous grin and I blushed furiously, snatching up my skirt to cover myself again.

"Naughty Harriet," she taunted. "What would grandmom say?" She got up and archly patted me on the backside. As we returned to the shop she continued to embarrass me by leading me to the underwear section and picking out some outrageously skimpy panties and thongs, proclaiming in her very loud American voice how perfect they were for me. She then chose for herself a skimpy tee shirt and we headed for the tills.All in all I was delighted to get everything paid for and escape to the sanctuary of the shopping centre.

Being with Fetishdoll was a rollercoaster ride of the emotions, that was for sure. She was so unpredictable, so brashly self-confident and so decisive that being with her was like being caught up in a maelstrom. Everything she said or did seemed to her to be entirely natural, even when it was the most extraordinary thing. She appeared to think there was nothing unusual in inviting herself to dinner with someone she had never met; or to appear out of nowhere in a shop changing room; or to invite herself home for supper, which was what she now did.

"What are you cooking tonight?" she asked.

I had given up being astonished by her effrontery and sighed resignedly. "Pasta do you?" I asked.