I don't always get along with my sister Lilia. She's one year older than me and seems to think that that gives her the right to get her own way all the time. We share a room, the two of us, and we always have. I would suggest that we should have separate rooms these days, since I turned fifteen last week, but we live in a small house so we don't have much choice. I did broach the subject of moving once with Dad, when I was thirteen, but he snapped at me to stop being silly so I haven't mentioned it since. I know he was just in a bad mood that day, but I think it might be more than that. Maybe Dad just really loves this house.

I don't see much of Lilia at school. I spot her sometimes, with friends, and I used to give them a smile or a wave but they'd just look at me oddly and I began to wonder if Lilia even acknowledged that I was her sister. I suspected that she didn't, since she wouldn't come near me at school and never has her friends over. I stopped smiling at them well before the end of year seven and, in defiance, also stopped talking about my cool older sister and ignored her at home when my friends were round. It sometimes annoys her, and she'll stand behind them pulling stupid faces and trying to distract me while we talk, but I don't get angry. I force myself to block her out, and my friends seem to have cottoned on to this because they ignore her too. She doesn't do it so much anymore, but often won't speak to me after they've left. Or she'll throw a fit.

I don't like her fits. When we were children she used to break my toys when she was cross and I'd go crying to Mum and she'd say, "There, there, I'm sure she didn't mean to." Then, as I got older, Mum would get annoyed at me if I told her. So did Dad. I don't understand why, but I suppose they just don't believe that Lilia does these things to me. She's never been punished. Maybe she's the favourite child. As they got less patient, Lilia got more violent. She wouldn't just slyly break my things anymore; she'd scream and hit me, pinch my arms and scratch the tender undersides of my knees, hurl things at the wall in fits of anguish. Mum started telling me to grow up and stop blaming my wickedness on Lilia, so I stopped telling her when Lilia acted up. I'd apologise meekly while Lilia sat upstairs in the chaos she had made, stroking a headless teddy bear or fiddling with the amputated limb of a plastic giraffe. She'd cackle cruelly when I joined her later, pleased with herself for getting away with it.

The most recent incident was last week. I'd spent every night all week on my geography project and Lilia started to get angry that I wasn't paying her attention. I told her to go away. I saw the anger flare in her eyes and she ran downstairs and came back with a box of matches. I begged her not to, but she struck a match along the side of the box and smiled as the flame leapt up. It cast an odd colour across her face, lighting up her chin but leaving her eyes in shadow. The expression on her face was eerie, it scared me, but I tried to grab at the match and blow it out. I burnt myself in the struggle, the tip of the flame nipping the palm of my hand, and I was too late anyway. She dropped the match onto my pile of carefully inked papers and laughed as the whole lot went up in flames. I was sobbing when Mum came home. I tried to tell her what had happened. She slapped my cheek. There's still a man-hole sized burn on my carpet. Dad said I'd just have to live with it as punishment for what I'd done. I opened my mouth to protest that it was Lilia and why would I burn my own project? But I thought better of it. I didn't need a second stinging cheek.

Then today something strange happened. We were arguing. She was screaming at me that I should talk to her and only her and didn't I understand that she was only trying to protect me from all the awful people in this world? I was ignoring her, standing my ground and staring blankly into her face. She kept screaming at me, shrieking louder and louder until it was all I could do not to clamp my hands over my ears at the racket. I heard the front door and thought, good, they'll finally see her for what she really is.

"Keep screaming, Lilia, you won't be the angel child any longer," I said calmly. She snarled, a hideous sound that shook me more than any human sound should, and grabbed hold of the glass bowl I kept my lavender in. She raised it and hurled the lavender towards me then, stepping backwards towards the wall, smashed her hand and the bowl against the plaster. Blood dripped from her fingertips and, with another unearthly screech, she leapt at me, the hand of glass looming towards my face. I screamed. It was at that moment that our bedroom door burst open and my Dad, his face white with panic, appeared on the threshold. He stopped. He stared.

"Isobel?" he whispered.

My scream stopped. The hand in front of my face froze, the shards of glass still clutched in my bleeding fist. I suddenly realised that I was the only person in my room.