You see, it was like this:

I knew it as soon as he touched me. I could feel it oozing from his long, pale fingers clasping my hand; it was a dark, oily poison seeping into me. It crept up my arm and spread out through my whole body. A thin film of malevolence settled on my mind. All of a sudden, the day looked gloomy.

Even before this sinister surge hit me, I regretted having approached him. When I saw his crooked nose and crippled left hand, I recoiled inwardly. But it was fresher's week, I had just arrived at the hall and I had shaken hands with the other two students in the kitchen. Some might think this old-fashioned of me, but I felt that since we were all going to live on the same corridor, I should introduce myself properly, Hello, my name is Lucy, pleased to meet you, etc etc. I was brought up to be polite. I couldn't have foreseen that I would become infected with evil from a handshake.

He soon slunk away, while I stood chatting with the other two. Gemma, it turned out, was on my course. She was an impressive brunette with curls down to her bum and a certain twinkle in her eye. We immediately made plans to help each other study. And then Amy, much more inconspicuous, did English literature. They were both from up North. The last two rooms on this floor, Amy told me, were occupied by a couple, Kevin and Louise.

"They're very sweet together," said Gemma. "Wait till you meet them, it'll make you want to get married straight away."

"They're married?"

"No, but it's only a question of time." She laughed and handed round a packet of cookies.

The sun came out again and shone across the crumb-strewn floor. I blinked a few times and glanced at my hand. I wasn't so sure anymore about what had happened earlier. I went away to my room to unpack. Gemma came and sat on my bed while I shoved t-shirts into the wardrobe.

"We'll have a great time together," she said. She returned my smile. "Well, not with him, maybe." She made a vague movement with her head and I knew who she meant. "Bit of a loner, I think. Anyway the rest of us on this floor are going to party!"

I phoned mum to tell her I had arrived okay and met my hall mates. She wanted to know what the bathrooms were like and whether there were lockable fridge compartments. I'd paid no attention to either. And then she said, for the umpteenth time:

"Don't get involved with any dodgy people, Lucy. I hear such terrible stories about students doing alcohol and worse…"

"Mum, you know I've always been sensible."

"Well, just take care you make nice friends."

"Sure. I've met two nice girls already. One of them is really great, I think she could become my new best friend."

Later that day, I deliberately stepped on a snail that had almost made it across the footpath behind the library. The feel of the shell crunching under my sole made the back of my neck tingle. I walked on with a wide grin on my face.

Lying in bed that night, the image of the crippled hand and the eerie feel of his touch chased round and round in my head. I tried to tell myself that it was nothing, just some silly illusion. I didn't believe in Evil Personified. Certainly in my line of study - term hadn't even started properly, but I was already thinking that way - we had no track with the supernatural. Then I remembered the snail and the pleasure it had given me to wipe out its tiny life. I got up and dragged my bed away from the wall. His room was on the other side. I pulled the duvet around me and tried to sleep. In the morning, I would rearrange the furniture more permanently.

When morning came, I showered and showered. Afterwards I felt clean and new and ready to face the world with a kindly smile. I went into the kitchen. He sat at the table, his crippled hand curled into his sleeve, leather trousers creaking as he bent over a cereal bowl. The hand that held the spoon was crowned by a row of grinning silver skulls. He said hello. I muttered some excuse and fled without breakfast.

On my way to the main building, I passed a bike rack. I slowed down and unpinned the brooch from my lapel. It was only just after eight o'clock, hardly anyone around. I waited for the few early birds to pass. Then I thrust the pin into the front tyre of the first bike on the rack. I got through three more before I saw someone coming up the path. The feelings that pulsed through me as I walked away were disturbing; smug triumph mixed with both spite and guilt.

Later that day I met Kevin and Louise. Just as Gemma had said, they were very sweet together. She was really tall and he simply looked up to her. They sat side by side like conjoined twins and were just so made for each other. So why did I feel resentment? Why did I secretly wish I could wipe that blissful smile of Louise's face? I cast a look around the room and saw him sitting in the corner with a magazine. The cover showed a skull with daggers protruding from the eye sockets. So there was my answer.

Not the best start to university life, is it? And I continued the way I had started. I punctured more tyres. I ripped ads off the notice boards or defaced them with nasty comments. I trod on every critter that crossed my path and I kept score on a notepad. Five spiders, six beetles, three woodlice, one butterfly, three slugs. And the snail, of course.

After about a week, the effect wore off and I felt myself again. I resolved never to go near him or even speak to him. I didn't know what to do about the damage I had caused, since I had no idea how many bikes I had vandalised or who they belonged to. And, of course, I couldn't bring those creepy-crawlies back to life. But somehow I had to make amends. I looked online and found a few charities I liked, so I donated rather more than I could afford. That afternoon he walked past me as I stood in the cafeteria queue and casually brushed against my fingers that were holding the tray. I was tainted again.

You would expect him to have some ominous name like Malvolio, or go by a nickname that suggested dark secrets, but he was called plain Alan. Alan McNeil. He was on my course. Unlike in the hall, where he said very little, he was eloquent and brilliant in class. I found his cleverness creepy and suspected that he came by his knowledge in sinister ways. In my mind I called him Evil Al. In reality he had no nicknames. He made no friends.

I made friends. I'd always made friends easily. There was a boy on the course called Jack, short, cute and jolly, who became pally with me very quickly. He reminded me of my mischievous cousin Ben. Amy, Gemma, Louise and I formed a girly quartet with Kevin as an honorary fifth member. Pub nights, club nights, pizza nights, movie marathons, the lot. We were leading the student high life and none of them knew…

Things came to a head on Louise's birthday. Her parents had sent her a parcel with a beautiful silk scarf in blue and purple. She was delighted with it. As Gemma lit the candles on the cake, I couldn't help staring at the flames, and at the scarf, and then at the flames again. The colours suited Louise's blonde hair way too well. By Wednesday afternoon, the scarf lay crunched up under my bed with several holes burned into it. When I met Evil Al on the stair that evening, he smiled at me. I knew it was his way of acknowledging the scarf thing. Dismayed, I mumbled hello and rushed past him.