When the last sounds had faded, the boy came sloping up the stairs. He was heading for the balcony, to keep an eye on his friend Steve and see that he came to no harm. If he made it up there, his fate would be sealed and he'd have to live the tormented life of a half-vampire. I had the power to change that. This, in addition to freedom from the Lake of Souls, was Evanna's gift to me – and the last part of the gift as far as Mr Tiny was aware.

As young Darren drew close, I launched myself at him, picked him up before he knew what was happening, and ran with him down the stairs. I burst through the door into the light of the corridor, then dumped him roughly on the floor. His face was a mask of terror.

"D-d-d-don't kill me!" he squealed, scrabbling backwards.

In answer I tore my hood back, then ripped off my mask, revealing my round, grey, stitched together face and huge gaping maw of a mouth. I thrust my head forward, leered and spread my arms. Darren screamed, lurched to his feet and stumbled for the exit. I pounded after him, making lots of noise, scraping the wall with my fingers. He flew out of the theatre when he got to the door, rolled down the steps, then picked himself up and ran for his life.

I stood on the front door step, watching my younger self flee for safety. I was smiling softly. I'd stand guard here to be certain, but I was sure he wouldn't return. He'd run straight home, leap beneath the bed covers and shiver himself to sleep. In the morning, not having seen what Steve got up to, he'd phone to find out if his friend was OK. Not knowing who Mr Crepsley was, he'd have no reason to fear Steve, and Steve would have no reason to be suspicious of Darren. Their friendship would resume its natural course and, although I was sure they'd talk often about their trip to the Cirque Du Freak, Darren wouldn't go back to steal the spider, and Steve would never reveal the truth about Mr Crepsley.

I retreated from the entrance and climbed the steps up to the balcony. There, I watched as Steve had his showdown with Mr Crepsley. He asked to be the vampire's assistant. Mr Crepsley tested his blood, then rejected him on the grounds that he was evil. Steve left in a rage, swearing revenge on the vampire.

Would Steve still seek out that revenge now that his main nemesis – me – had been removed from the equation? When he grew up, would his path still take him away from normal life and towards the vampaneze? Was he destined to live his life as he had the first time round, only with a different enemy instead of Darren Shan? Or would the universe replace Steve, like me, with somebody else?

I had no way of knowing. Only time would tell, and I wouldn't be around long enough to see the story through to its end. I'd had my innings, and they were just about over. It was time for me to step back, draw a line under my life, and make my final farewell.

But first – one last cunning attempt to wreck the plans of Desmond Tiny!

The key events of the past can't be changed, but the people in it can. Evanna had told me that if she went back and killed Adolf Hitler, the universe would replace him with somebody else. The major events of World War II would unfold exactly as they were meant to, only with a different figurehead at the helm. This would obviously create a number of temporal discrepancies, but nothing the higher force of the universe couldn't set right.

While I couldn't alter the course of my history, I could remove myself from it. Which was what I'd done by scaring off young Darren. The events of my life would unravel the same way they had before. A child would be blooded, travel to Vampire Mountain, unmask Kurda Smahlt, become a Vampire Prince, then hunt for the Vampaneze Lord. But it wouldn't be the boy I'd frightened off tonight. Somebody else – some other child – would have to fill the shoes of Darren Shan.

I felt bad about putting another kid through the tough trials of my life, but at least I knew that in the end – in death – he would be triumphant. The person who replaced me would follow in my footsteps, kill the Vampaneze Lord and die in the battle, and out of that death peace would hopefully grow. Since the child wouldn't be responsible for his actions, his soul should go straight to Paradise when he died – the universe, I hoped, was harsh but fair.

And maybe it wouldn't even be a boy. Perhaps I'd be replaced by a girl! The new Darren Shan didn't have to be an exact replica of the old one. He or she could come from any background or country. All the child needed was a strong sense of curiosity and a slightly disobedient streak. Anyone with the nerve to sneak out late at night and go see the Cirque Du Freak had the potential to take my place as Mr Crepsley's assistant.

Since my part would change, the parts of others could change too. Maybe another girl – or boy – would fill Debbie's role, and somebody else could be Sam Grest. Perhaps Gavner Purl wouldn't be the vampire who was killed by Kurda, and even Steve could be replaced by another. Maybe Mr Crepsley wouldn't be the one to die in the Cavern of Retribution, and would live to be a vampire of ancient years and wisdom, like his mentor, Seba Nile. Many of the parts in the story – the saga – of my life might be up for grabs now that the central character had been changed.

But that was all wild speculation. What I did know for certain was that the boy I'd once been would now lead a normal life. He'd go to school, grow up like anybody else, get a job, maybe raise a family of his own one day. All the things the original Darren Shan had missed out on, the new Darren would enjoy. I'd given him his freedom – his humanity. I could only pray to the gods of the vampires that he made the most of it.

The objects stitched into the lining of my robes were my diaries. I'd kept a diary just about as long as I could remember. I'd recorded everything in it – my trip to the Cirque Du Freak, becoming Mr Crepsley's assistant, my time in Vampire Mountain, the War of the Scars and hunt for the Vampaneze Lord, right up to that final night when I'd had my fatal last run-in with Steve. It was all there, everything important from my life, along with lots of trivial stuff too.

Evanna had brought the diary up to date. She must have taken it from the house where Debbie and Alice were based, then described all that had happened on that blood-drenched night, the showdown with Steve and my death. She'd then briefly outlined my long years of mental suffering in the Lake of Souls, followed by a more detailed account of my rescue and rebirth as a Little Person. She'd even gone beyond that, and told what happened next, my return, the way I'd scared the original Darren away, and…

I don't know what she wrote in the last few pages. I didn't read that far. I'd rather find out for myself what my final actions and thoughts are – not read about them in a book!

After Steve left and Mr Crepsley retired to the cellar where his coffin was stored, I went in search of Mr Tall. I found him in his van, going over the night's receipts. He used to do that regularly. I think he enjoyed the normality of the simple task. I knocked on the door and waited for him to answer.

"What do you want?" he asked suspiciously when he saw me. Mr Tall wasn't used to being surprised, certainly not by a Little Person.

I held the diaries out to him. He looked at them warily, not touching them.

"Is this a message from Desmond?" he asked. I shook my neckless head. "Then what…?" His eyes widened. "No!" he gasped. "It can't be!" He pushed my hood back – I'd replaced it after I'd scared off the young me – and studied my features fiercely.

After a while Mr Tall's look of concern was replaced by a smile. "Is this my sister's work?" he enquired. I nodded my chunky head a fraction. "I never thought she'd get involved," he murmured. "I imagine there's more to it than just freeing your soul, but I won't press you for information – better for all concerned if I don't know."