By the time we entered high school, he had become angrier and angrier inside. The last time I saw his bedroom, everything breakable inside of it was destroyed. Shattered glass littered the floor from the broken lamp, the smashed ornaments and the cracked window. The mattress was in tatters, the bed frame cracked, and every ledge on the bookshelf was split in half. Even the brightly-coloured wallpaper was ripped from the walls.

He stopped sleeping properly. Dark circles began to form under his eyes; his hair became matted and unkempt. He seldom ate, becoming scrawny and thin, and very pale. He stopped taking care of himself on the whole. No amount of persuading on my part could encourage him to do otherwise. He was a silently ticking time bomb, the slightest touch to which would set it off.

But in my opinion, I think it was the Halloween incident that finally made him snap.

There was always one kid who made fun of him. Billie Ferguson, I think her name was. She was a senior, and one of those popular type girls that nobody actually liked, but they were too scared to admit it so she had lots of friends anyway. She was attractive and knew it; she wasn't afraid to flaunt her beauty to get what and who she wanted. Billie was nice face-to-face, but trash-talked and gossiped about everyone in the school behind their back. But to people she didn't like, she was just an out and out bitch. And one of those people happened to be him.

We were sixteen, and I think that particular October 31st was the last time I was ever able to actually make him do anything with me. I was also fairly sure this would be the last time we would ever go trick-or-treating, as we were getting older and starting to drop such child-like things. At least, I was. He never did much of anything, to be honest, except add to his collection of knives and torment any living thing that he could. I tried to include him in most of the things that I did, because I knew that he would never go out and do them on his own. And besides, I didn't like the idea of him rotting away his entire life and never experiencing anything.

I'd bought him a mask to wear while I dragged him around the neighbourhood. He put it on, albeit reluctantly, commenting: "What's the advantage of anonymity if it only lasts for one night? It would be much more beneficial to be always unidentifiable, to everyone."

I assured him that it was all in good fun, and asked him why in the world any person would never want anyone to know who they were. His answer: "Because having no identity means that you're no one. And when you're no one, you can be anyone."

I tried not to speculate too much on what kinds of meanings this explanation might have. I would never be able to comprehend the way his brain worked. Instead, I pulled him out the door and into the street full of trick-or-treaters.

It had gotten quite late. The steady streams of trick-or-treaters had slowed to the rare one or two every so often. The night was black with a new moon, and I would have had a hard time seeing my own hand in front of my face had it not been for the dim streetlights along the sidewalk, though truthfully they didn't help all that much.

While we were crossing the lawn in front of house 10 234 up to the steps, we were stopped by Billie Ferguson, heading the opposite way across the same lawn. As soon as I saw her, I knew she'd been looking for us.

"Know what I'm dressed up us?" she asked us sweetly. Her pretty face was covered with messily applied white paste, and two black smudges were untidily blotched around her eyes. But it was the finishing touch that really got me: the angry red that painted her mouth was also smeared sloppily up the sides of her face.

She turned to face him and grinned, flashing her perfect teeth. "You really don't know? All right then, I'll give you a clue: they look like a clown."

"Leave us alone, Billie," I said. I was positively seething. I knew I wouldn't do anything to her, and so did she. But I also knew that I couldn't account for his actions too, he was too unpredictable. This was what made me uneasy.

Billie ignored me. "Have you guessed yet? No? Well, see this?" She pointed to her mouth and grinned. "I'm always smiling. Remind you of anyone?"

"Billie," I warned.

"Chrissy," she mocked, laughing.

She stepped closer until she was only inches away from him, reached up, and pulled off his mask, discarding it on the grass beside her. He stood there silently, impassive as she ran her fingers slowly over the scars on his face, her eyes glinting. I watched nervously.

Her mouth twisted derisively as she leaned up and whispered something into his ear that I could not hear.

All of a sudden, his eyes blazed. Before I could shout a word of warning, he'd grabbed her and thrown her up against the wall of the house. Billie squeaked and struggled as he held her there with one hand, reaching into his pocket with the other. My heart pounded a million miles an hour against my ribcage. I had never realized he was so strong.

Her eyes went wide with horror as he slowly pulled out a pocketknife and held it up to her face.

"You want to know how I got these scars?" he asked her. Billie whimpered.

"One day, I'm walking home after school and I get stopped by this guy. He pulls me into an alley, and shoves me against a wall, telling me to give him all my money. I tell him I have no money, and ohhhh, no, he's not too happy about that." He clicked his tongue on the last letter, making the word sound sharp and severe.

"So he pulls out this knife, and sticks it in my mouth, like this." He stuck the knife in Billie's mouth, making her wail and squirm. "And he gives me these." He grinned and cackled, turning his head from side to side so she can see his scars better. Billie bit back a sob.

I knew I had to stop him now, or he wouldn't stop. He had that look in his eye; the same one I saw when he was ready to take the life of one of his numerous torture victims.

I approached him slowly. I put a hand on his arm and he looked down at me.

"Stop," I said.

"Why should I stop when the whole time she's been telling me to GO?" he asked me, his eyes dark and wild. He pushed the knife hard against the side of Billie's mouth.

A bead of blood appeared. A tear rolled down Billie's face, a trail of dark make-up running over the white on her cheek.

"Please," I begged him. "Stop. Do it for me."

I'd never felt so helpless, or so scared. Adrenaline pumped through my veins like it was the only thing my blood was made of.

He stared down at me, his face contemplative. That moment seemed to last forever.

Finally, he dropped Billie. She fell in a sobbing heap on the ground. The blood from the side of her mouth a grisly darker colour against the red of her make-up, and dark streaks ran down her face and neck as she cried.

I grabbed his arm and led him away quickly. That look had not disappeared from his eye, and I was afraid for what might happen if we stayed. I left him on his doorstep and hurried home.

To this day, I still don't know why he stopped then. If it was for me, though I highly disbelieve that it was, I thank him for it with all my heart. Whatever other inconceivable reason it might have been, though, I was just glad that he had stopped.

That night in bed, I stayed up all night worrying if she would press charges against him. As I did so, my mind drifted to the story he had told her. I wondered if it was true. Somehow, I didn't think so.

The next morning, Billie Ferguson was found dead in her front yard. She had bled to death from a stab wound to the neck. Imagining that, bleeding profusely and unable to call out, only a few feet away from people who could have helped her, sickened me.

Did it surprise me that she had wound up dead? Astonishingly, no, it didn't. I couldn't condone the fact that it was him, without a doubt, who had murdered her. But even as I returned to school the next day, I couldn't quite bring myself to desert him. I was all he had. I didn't have the heart.

I never asked him about Billie's death, and he never told me about it.

I always had my own suspicions of how he'd gotten those scars. Both his mother and father were heavy drinkers, and they held hardcore drinking parties each and every weekend. Their ring of friends that attended these parties weren't much better. None of them cared much for anything unless their system was shot full of alcohol.

Once I'd been over to his house when we were seven, and they were hosting one of these parties. We hid in his bedroom the entire time. He wouldn't let me leave the room for anything. The one time he ventured out to get a snack for us, I heard crashing and screaming from the kitchen. When he returned to the bedroom, there were already purpling bruises on his face and neck.

It was inevitable that eventually someone would inform the authorities. When we were in the eleventh grade, he was taken away from his parents and sent to live in a foster home in another part of the city. Some time later, I heard that he'd run away.

He didn't try to contact me, or visit me. It was almost as if he'd dropped off the face of the earth. But I never forgot him.

People began to approach me and talk to me after he left; I made new friends. I graduated from Gotham High. My eighteenth birthday came and went. I moved out of my parents' house, and was working at three part-time jobs so I could make enough money to get into a good university.

Then one night, I heard a knocking on my window.