Take fairy tales, for instance. Fairy tales are some of the most viciously evil stories I’ve ever read, but we tell them to kids. ‘Sweet dreams’, we say, apparently blissfully unaware that we’ve just read them a story where a mother sends her daughter, dressed like a Star Trek security guard, alone and unescorted into a forest which she knows is home to a rather nasty wolf. Also, just in case the prospect of a defenceless child isn’t enough to tempt the Big Bad out of hiding, she gives her a basket of food. I can only assume the local store was out of big neon signs reading ‘Come and Get It!!’ because otherwise she would surely have had one of them too. Add to this the gruesome murder of Granny and you have a story Wes Craven would have sold vital organs to think up.

My mum used to read me those stories when I was a kid. I always liked them.

I was discussing this particular literary conundrum with Caroline and Sandra when She suddenly came round the corner. ‘She’ is Julie, my sister; two years above me and the undisputed queen of the school. You might think having royalty in the family would be useful, and if we liked each other then you’d be right. But we don’t. We detest, loathe and despise each other with the kind of hatred born in the fiery pits of Hades. My friends are all targets by proxy.

This time we got off pretty lightly; a swapped evil look and some giggling from her entourage was as far as it went. She’s got a flock that follows her around - a group of girls her age and one or two favoured boys. The men tend to be replaced pretty swiftly. I think they may have some kind of time-share system going.

You might ask just why is she queen? What makes her so special? You wouldn’t say that if you’d met her. She’s queen because she’s a trendsetter - she’s fashionable, she’s cool, and most importantly she is drop-dead gorgeous.

I hate her more for that than anything else. It’s jealousy, pure and simple. You’d never tell we were sisters to look at us. She’s tall, slim, has hair that always lays perfectly and shimmers in a way that’s the exact opposite of greasy, boasts a perfect stomach and has enough curves to give any boy fevered dreams. I, on the other hand... I’m not ugly, but Julie’s very firmly at the top of the Premier League. I’ll be lucky to ever make higher than the second division.

We tried to put a curse on her once. It wasn’t anything serious, of course. Caroline and Sandra were spending the night at my place and we were spending the time bitching about Julie. It just kind of came up in the conversation.

"She totally embarrassed me in front of John yesterday," Sandra said, laying back on my bed and glaring accusingly at the ceiling. "I reckon I’d almost pulled him, too."

"You pulled John?" I asked, amazed. "He’s gorgeous!"

"Bloody right he is," Sandra said. "And if it wasn’t for your sister I could’ve been tongue-wrestling with him about now. Just wish I could get the bitch back."

"Let’s curse her," Caroline said, in that psychotically velvet voice of hers.

"Sweet Jesus," Sandra laughed, sitting up, "Morticia strikes again."

"It might work," Caroline replied. "Wouldn’t you like to hear her scream when she wakes up tomorrow covered in huge spots?"

Sandra snorted, and I smiled. "What do we need?"

I suppose it might have worked - Julie got her first zit three days later, a small one on her cheek. Caroline was completely rhapsodical about it, going on about bigger and better spells we could do. Sandra was a little more sceptical. She thinks it’s all a bit pathetic, this magic and mysticism, while Caroline is totally obsessed by it. She’s got all the trimmings - dyed black hair, black nail varnish and dozens of books on witchcraft. She’s been to see Macbeth five times just because of the witches, and has loads of those horrible scented candles burning in her room. I’ve got a horror movie fixation and left it at that. I’ve never seen the point of scented candles, especially when all they ever seem to smell of is wax.

I’ve always treated magic as a bit of fun. Caroline treats it as a religion. That’s something she’s got in common with Julie; they both worship images of some kind, but while Caroline looks into the black world of the occult, all Julie has to do is look in the mirror.

Shall I give you an example? Not long ago, it was the eighteenth birthday of one of her friends, so they were all taking the excuse to go out and get ratted. Our parents don’t usually let her out like that on a school night, but they figured as it was an eighteenth birthday it was special. Julie can take forever to get ready and most of that time is spent in front of the mirror - tweak the top to reveal just the right amount, flick the hair down over one eye, spend the next three days gazing lovingly at her reflection.

She’s got a full-length mirror in her room. Whenever she’s a bit depressed she can go and look at herself in it, just to remind her how beautiful she is. It’s pathetic.

Personally I’ve never liked mirrors. Maybe it is just because my reflection isn’t quite as appealing as Julie’s is, but I’ve always found them a bit creepy... just standing there, totally impassive, showing you something so similar yet so opposite in every way. It’s a golden rule - never trust anything you can’t out-stare.

She came downstairs in some lightly flared red jeans and a black belly-top so tight I can only assume it was designed for the discerning stick insect, plus of course the lovingly applied lipstick and mascara.

"How do I look?" she asked.

"Oh, darling! You look gorgeous!" Mum cried. "Lucy, doesn’t your sister look gorgeous?"

"She looks like a desperate hooker," I snapped, except I didn’t. That’s what I wanted to say, but what came out was more along the lines of a dead monotone "Yeah. Gorgeous." Neither me nor Julie is quite suicidal enough to be really bitchy in front of our parents.

Julie smiled like a princess and scampered back upstairs. I rolled my eyes as inconspicuously as possible and followed, deciding to shut myself up in my room for a while and spare myself any more of her catwalk prancing. As I reached the landing I saw Julie’s door was open a crack, and I couldn’t resist taking a quick look inside. She was, as expected, standing in front of the mirror. She struck a couple of poses, pulled some hair around her shoulder, then raised her arms and head into an almost crucified position.

"Mirror, mirror on the wall," she intoned, "who is the fairest of them all?"

I told Sandra and Caroline about it the next day and we all had a good laugh.

"She really said that?" Sandra asked, trying hard not to burst out laughing. "I knew she was vain, but..."

"I know," I laughed, not making any suppressive effort at all. "She’s completely in love with herself. I reckon she’s got some kind of schizophrenia thing going."

"Quiet," Caroline interrupted, suddenly. "Something wicked this way comes."

We stopped talking and instantly heard Julie’s indignant whine from around the corner. Like GIs hiding from the enemy we dived into the nearest doorway, which turned out to be an empty office. Caroline pushed the door to the jar and we all stared at the procession through the crack.

"-and I’m like hello, I’m here, over here, this way and he’s still sat at the front going Julie White, has anyone seen Julie White? I swear it was like I was totally invisible. What else was I supposed to do, dance on the table? Honestly, the guy must be blind. Oh, damn."

Some of her hair had fallen out of place with the last exclamation. Julie paused by the window to fix it and her courtiers obediently shuffled to a halt behind her.

Julie stared into the window to fix her hair. I looked at her reflection, and tried to shake off the feeling that it was looking back.

Julie was in a good mood this morning. That’s never a good sign, because when she’s in a good mood she gets so much more pleasure from tormenting me, and school mornings are awkward enough as they are. I always try to get into the bathroom first because she takes so damn long, but this time I hadn’t managed it, so there I am banging on the door with ten minutes till the bus arrives while Julie does her lipstick.

"Get on with it!" I yelled.

With exactly two minutes to go the door opens Her Highness struts out, smiling sweetly.

"Honestly, Luce," she said. "What’s the rush? Let’s face it, nothing short of a major operation is going to make you look any better."

I scowled but the brilliant retort didn’t come. It wasn’t until two hours later that I thought of saying: "Maybe. I’ll have to ask your pimp how much he paid for yours." I mentally bookmarked that one for later use and carried on talking to Caroline. The conversation was a mildly twisted one about how we could persuade Celine Dion to give up singing. I’m almost certain thumbscrews were involved somewhere.

We must have been really deep into the discussion, because in the middle of a long, straight, comparatively empty corridor we bumped into Julie, and for ‘bump into’ read ‘crash head-first without slowing and end up in a sprawling heap on the floor’.

"Where the hell’d you come from?" Caroline asked, irritably. Until we’d hit neither of us had noticed her.

Julie echoed the question, then shook herself. "Get out the way," she snapped. "I’ve got to go tell the dog pound we’ve got a couple of strays hanging round."

She stormed off, and Caroline mentioned that she’d found a spell to make a voodoo doll, just, you know, if I was interested. I was very, very interested.

It turns out it’s not really all that hard. According to Caroline, any old doll will do. It’s just a matter of what you put with it. You need a photo or some image of the target, the more accurate the better, something the target really values and something of the target herself. None of that sounded too hard. I was a little uncertain on what she might value, but figured I could probably ad-lib.

Now, when planning an operation like this, secrecy is of the utmost importance. If I was caught stealing Julie’s things then there would be hell to pay from every corner, and not even getting back at Julie is worth that. However, it happened that I was in luck. It was a Wednesday, and every Wednesday Julie hangs around town with her mates for a while before coming home. I couldn’t see Mum being a problem, so when I got home I’d have some searching time.

I don’t get many opportunities to go around Julie’s room. Whenever she’s there it’s very firmly out of bounds. It’s not really anything special. She’s got a few posters put up on the walls, all the usual furniture. The mirror’s set up opposite the wardrobes, huge and glaring. Pink curtains drape the window, horrible papery things that feel like they’ve been made out of kitchen-roll. I pulled one to one side and scanned the street. There was no sign of my sister.

The first thing I looked for was a photo. I found it hard to believe that anyone who loved to look at themselves as much as Julie did wouldn’t have a few lying around. A quick search of her desktop proved fruitless, but taking one from there would have been a bad idea anyway as she was sure to notice. Instead I began to rifle the drawers; most were clothes but at the bottom I found one filled with random junk. A couple of old aerosol cans, a book, a few pens and, hidden at the bottom, a collection of old passport photos, reams and reams of them. Some were just of her, most also had a friend or ex-boyfriend. One in particular looked very tatty. She’d looked at him a lot.

I pocketed one of the more pristine strips - the ones she kept in best condition, I noticed, were the ones that only featured her - and turned my attention to the other treasures held inside.

The book also looked incredibly well-thumbed. With rising anticipation I opened it - a diary. I had no idea Julie kept one of these, and it ought to make a damn good read. I looked at the first page. Why is it, she had written, why is it that people always seem to think agreeing with me is more important than listening to me? Some of the ink looked smudged.

I slipped the book into my pocket with the photos, and tried to remember what else I had come in for. Standing up, I found myself staring straight into the mirror. My reflection looked blurry... the movements were odd. It looked taller than I remembered, and a bit more shapely. I moved and it did too, but it seemed fuzzy, sluggish. I got the feeling that I really didn’t belong in that mirror, but I couldn’t bring myself to move away.

The front door slammed shut downstairs. Julie called out to Mum that she was home and began to stomp upstairs. I ripped myself out of the mirror in a panic. I couldn’t leave the room - it opened practically onto the stairs so she’d be sure to see me if I did. Sweet Jesus, she’d never been home this early before! I looked around wildly for somewhere to hide... under her bed, that would work, or at least it would if it wasn’t full of boxes... where else? Only one option.

I squashed myself into a wardrobe, pulling the door shut just as my sister came in and flung herself on the bed. She was really upset about something. After a minute she got up and stared at herself long and hard in the mirror. Her reflection was perfectly vivid, but something still didn’t seem right about it.

"Well," she said, at last, "I can see me. Is it too much to ask that they do too?"

She kept on staring, and I suddenly clicked what was wrong. Her reflection had a shadow, going into the mirror. Julie didn’t have one at all.

I told Sandra and Caroline the next day. I’d wanted to tell them that night, but the only phone we have is downstairs, in easy listening distance of everyone. I didn’t want to risk it. I spent most of that evening going through Julie’s diary, but it wasn’t as revealing as I had hoped. A lot of it was slushy drivel about whether or not she’d ever find her One True Love. I could barely stomach reading it.

Despite her obsession with the black arts, Caroline had never heard of anything like it. She wanted to come over and try to sneak a look for herself, maybe light a couple of candles or something.

"How would that help?" I asked.

"I don’t know," she shrugged. "I just like candles."

Belief wasn’t even an issue with her; she would accept anything vaguely paranormal. Sandra, on the other hand, took all things like this with a truckload of salt. What makes her scepticism all the more infuriating is that she has an annoying habit of being right.

"Are you sure you just couldn’t see it?" she asked, in that horribly Sherlock-Holmes way of hers.

"Yes!" I lied. I had sneaked looks at Julie all through last night. She had been as vile and solid as ever, her shadow in all the right places. But it hadn’t been there before. It had been in the mirror.

Caroline insisted on coming round to look for herself. I didn’t take much persuading - this was starting to scare me. Sandra feigned disinterest, but said she’d come too, ‘just to have a laugh at you two dozy sods playing Witches of Eastwick’.

We avoided Julie on the bus but kept a close watch on her. She was sitting as close to the window as possible, one hand pressed to the glass. It seemed to keep her in focus. Whenever the bus jogged and her hand lost contact she seemed to do the same thing with the world. It wasn’t really visible, more just a sense she gave off of not really belonging here.

When the bus pulled up at our stop we let her get off first, then tailed her home. Sandra gripped my arm tighter as she watched; Julie had lost her shadow again and the wind which was blowing my hair into my eyes wasn’t moving hers at all. Caroline was staring with a kind of hungry, horrified fascination.

She pressed one hand to the glass in our front door as she opened it, and lingered for as long as possible, as if she was incredibly loathe to let go. We lost sight of her when she entered the house - light passed right through her, but shadows engulfed her completely.

We sneaked upstairs. I began to open my door when Caroline put one hand on my shoulder.

"No," she said, pointing to Julie’s room. "I want to go in there."

"What if she’s in there?" I snapped.

"We’ve got to see what’s going on," Caroline replied, evenly, and gently pushed open my sister’s door.

Julie wasn’t there. Still, I crept inside as slowly as possible, trying to keep away from the mirror’s cold glaze. Sandra stuck with me, her hand still clamped to my arm, but Caroline was a lot more comfortable with it all. She went and stood in front of the mirror, gazing at her reflection.

"Wow," she breathed. "I’m gorgeous."

The mirror wasn’t being entirely accurate. It had made her taller, pushing out her chest and lengthening her legs. It was still reflecting Caroline, but Caroline in Julie’s shape. Mesmerized, Caroline walked closer to the mirror, reaching out a hand. As her fingers touched the glass the air snapped and she was flung backwards onto the bed.

Sandra finally let go and dived for Caroline. "Are you alright?" she asked.

Caroline pulled herself onto her elbows. "It bit me," she said, muzzily.

"You can’t touch it."

We all turned. Julie was standing in the doorway, and something was very wrong. We were in her room and she wasn’t screaming.

"It doesn’t want you," she continued, in that same detached, vacant voice. "It wants me. Only me." She walked over to the mirror and pressed her hands to the pane, echoing her reflection’s every move. "But it’s not going to get me. I’m not going to let it. Do you hear me?" she whispered at her reflection. "I’m going to smash you."

"Can’t do that, my dear."

Caroline, Sandra and I looked at each other to see who said that. Then, as one, we turned to the mirror. Julie’s reflection was gripping my sister’s hands, her ghostly fingers coming out of the mirror and intertwining. Julie stepped back, pulling her reflection out of the mirror with her. It finally let go of Julie’s hands and stood there, translucent and spectral. We could all tell it was really there, but still we could make out the lines of wall and furniture through the mirror-Julie’s body.

"There’s too much of you here to do that to me," the mirror-Julie continued. "Everything that you love."

"You can’t..." Julie mumbled.

"He left you. I could never do that." The reflection put her arms around my sister’s neck and drew herself up close. "It’s okay honey," she whispered. "It’s okay. I love you too."

And then they kissed. It started slow and became more intense as we watched, their bodies pressing closer and closer, the reflection flowing inside Julie, fighting her way in and pushing something else out... until there was only one, who gave out a small sigh of pleasure and fell to the floor.

"Julie?" Sandra asked, looking down at the smiling body nervously.

"No." I replied. I don’t know how I knew, but I did. This wasn’t my sister, it was a reflection of her, so similar and so opposite both at once.

"Look," Caroline whispered. "I can see her."

She pointed to the mirror. I went close and found she was right. You could see Julie, hammering on the glass. She wasn’t the reflection of the mirror-Julie, she was just an outline, only visible if you knew what to look for, a wraith just about hanging onto reality. She was trapped, helpless.

I looked at that mirror a long time. Julie had been horrible to me my whole life, made it her sole purpose to be my torturer, but she was still my sister.

Without looking at the mirror-Julie, still flat-out on the carpet, I swung my leg around and kicked the mirror as hard as I could. There was just enough time for Julie’s expression to change to one of pure horror before it... before she was shattered, the fragments cascading to the floor.

Please don’t delude yourself thinking up justifications for what I did. The truth is I’m simply not a nice person - I didn’t like Julie, so when I had the chance I got rid of her. Permanently. I’ve never placed much strength in family ties; it’s always the person that matters. If I had the chance to do it again, I would, and I’d do it exactly the same. Since that day I haven’t had one guilty twinge, not one sleepless night. It’s really quite astonishing just how easy I found it to become a murderer.