The smell of blood is sickening. Hundreds of carcasses hang from silver hooks, stiff, shiny with frosty blood. I know they're just animals — cows, pigs, sheep — but I keep thinking they're human.

I take a careful step forward. Powerful overhead lights mean it's bright as day. I have to tread carefully. Hide behind the dead animals. Move slowly. The floor's slippery with water and blood, which makes progress even trickier.

Ahead, I spot him… the vampire… Mr. Crepsley. He's moving as quietly as I am, eyes focused on the fat man a little way ahead.

The fat man. He's why I'm here in this ice-cold slaughterhouse. He's the human Mr. Crepsley intends to kill. He's the man I have to save.

The fat man pauses and checks one of the hanging slabs of meat. His cheeks are chubby and red. He's wearing clear plastic gloves. He pats the dead animal — the squeaky noise of the hook as the carcass swings puts my teeth on edge — then begins whistling. He starts to walk again. Mr. Crepsley follows. So do I.

Evra is somewhere far behind. I left him outside. No point in both of us risking our lives.

I pick up speed, moving slowly closer. Neither knows I'm here. If everything works out as planned, they won't know, not until Mr. Crepsley makes his move. Not until I'm forced to act.

The fat man stops again. Bends to examine something. I take a quick step back, afraid he'll spot me, but then I see Mr. Crepsley closing in. Damn! No time to hide. If this is the moment he's chosen to attack, I have to get nearer.

I spring forward several feet, risking being heard. Luckily Mr. Crepsley is entirely focused on the fat man.

I'm only three or four feet behind the vampire now. I bring up the long butcher's knife that I've been holding down by my side. My eyes are glued to Mr. Crepsley. I won't act until he does — I'll give him every chance to prove my terrible suspicions wrong — but the second I see him tensing to spring…

I take a firmer grip on the knife. I've been practicing my swipe all day. I know the exact point I want to hit. One quick cut across Mr. Crepsley's throat and that'll be that. No more vampire. One more carcass to add to the pile.

Long seconds slip by. I don't dare look to see what the fat man is studying. Is he ever going to rise?

Then it happens. The fat man struggles to his feet. Mr. Crepsley hisses. He gets ready to lunge. I position the knife and steady my nerves. The fat man's on his feet now. He hears something. Looks up at the ceiling — wrong way, idiot! — as Mr. Crepsley leaps. As the vampire jumps, so do I, screeching loudly, slashing at him with the knife, determined to kill…

One month earlier…

My name's Darren Shan. I'm a half-vampire.

I used to be human, until I stole a vampire's spider. After that, my life changed forever. Mr. Crepsley — the vampire — forced me to become his assistant, and I joined a circus full of weird performers called the Cirque Du Freak.

Adapting was hard. Drinking blood was harder, and for a long time I wouldn't do it. Eventually I did, to save the memories of a dying friend (vampires can store a person's memories if they drain all their blood). I didn't enjoy it — the following few weeks were horrible, and I was plagued by nightmares — but after that first blood-red drink there could be no going back. I accepted my role as a vampire's assistant and learned to make the best of it.

Over the course of the next year, Mr. Crepsley taught me how to hunt and drink without being caught; how to take just enough blood to survive; how to hide my vampire identity when mixing with others. And in time I put my human fears behind me and became a true creature of the night.

A couple of girls stood watching Cormac Limbs with serious expressions. He was stretching his arms and legs, rolling his neck around, loosening his muscles. Then, winking at the girls, he put the middle three fingers of his right hand between his teeth and bit them off.

The girls screamed and fled. Cormac chuckled and wriggled the new fingers that were growing out of his hand.

I laughed. You got used to stuff like that when you worked in the Cirque Du Freak. The traveling show was full of incredible people, freaks of nature with cool and sometimes frightening powers.

Apart from Cormac Limbs, the performers included Rhamus Twobellies, capable of eating a full-grown elephant or an army tank; Gertha Teeth, who could bite through steel; the wolf-man — half man, half wolf, who'd killed my friend Sam Grest; Truska, a beautiful and mysterious woman who could grow a beard at will; and Mr. Tall, who could move as fast as lightning and seemed to be able to read people's minds. Mr. Tall owned and managed the Cirque Du Freak.

We were performing in a small town, camped behind an old mill inside which the show was staged every night. It was a run-down junkyard, but I was used to that type of venue. We could have played the grandest theaters in the world and slept in luxurious hotel rooms — the Cirque made a ton of money — but it was safer to keep a low profile and stick to places where the police and other officials rarely wandered.

My appearance hadn't changed much since leaving home with Mr. Crepsley almost a year and a half before. Because I was a half-vampire, I aged at only a fifth the rate of humans, which meant that though eighteen months had passed, my body was only three or four months older.

Although I wasn't very different on the outside, inside I was an entirely new person. I was stronger than any boy my age, able to run faster, leap farther, and dig my extra-strong nails into brick walls. My hearing, eyesight, and sense of smell had improved vastly.

Since I wasn't a full vampire, there was lots of stuff I couldn't do yet. For example, Mr. Crepsley could run at a superquick speed, which he called flitting. He could breathe out a gas that knocked people unconscious. And he could communicate telepathically with vampires and a few others, such as Mr. Tall.

I wouldn't be able to do those things until I became a full vampire. I didn't lose any sleep over it, because being a half-vampire had its bonuses: I didn't have to drink much human blood and — better yet — I could move around during the day.

It was daytime when I was exploring a garbage dump with Evra, the snake-boy, looking for food for the Little People — weird, small creatures who wore blue hooded capes and never spoke. Nobody — except maybe Mr. Tall — knew who or what they were, where they came from, or why they traveled with the Cirque. Their master was a creepy man called Mr. Tiny (he liked to eat children!), but we didn't see much of him at the Cirque.

"Found a dead dog," Evra shouted, holding it above his head. "It smells a little. Do you think they'll mind?"

I sniffed the air — Evra was a long way off, but I could smell the dog from here as well as a human could up close — and shook my head. "It'll be fine," I said. The Little People ate just about anything we brought.

I had a fox and a few rats in my bag. I felt bad about killing the rats — rats are friendly with vampires and usually come up to us like tame pets if we call them — but work is work. We all have to do things we don't like in life.