"Also," I said, "they couldn't stop him when he was older. As he comes into his full powers, he'll grow incredibly strong. They'd have to keep him comatose to control him."

"No!" Annie shouted, her face dark with stubborn rage. "I won't allow this! There must be a way to save him!"

"There is," I said, and she relaxed slightly. "But it's dangerous. And it won't restore his humanity – it will merely drive him towards a different corner of the night."

"Don't talk in riddles!" Annie snapped. "What does he have to do?"

"Become a vampire," I said.

Annie stared at me in disbelief.

"It's not as bad as it sounds," I went on quickly. "Yes, he'd age slowly, but that's something you and he could learn to cope with. And yes, he'd have to drink blood, but he wouldn't harm when he drank. We'd teach him to master his urges."

"No," Annie said. "There must be another way."

"There isn't," Vancha huffed. "And even this way isn't certain. Nor is it safe."

"I'll have to trade blood with him," I explained. "Pump my vampire cells into his body, and accept his vampaneze cells into mine. The vampire and vampaneze cells will attack each other. If all goes well, Darius will become a half-vampire and I'll carry on as before."

"But if it fails, you'll become a half-vampaneze and Darius won't change?" Annie guessed, trembling at the thought of such a horrible fate.

"No," I said. "It's worse that that. If it fails, I'll die – and so will Darius."

And then I sat back numbly and awaited her decision.

Annie didn't like it – nobody did! – but we eventually convinced her that there was no other solution. She wanted to wait, think it over and discuss it with her doctor, but I told her it was now or never. " Vancha and I have a mission to complete," I reminded her. "We might not be able to come back later."

When we'd first discussed the transfusion, Vancha had volunteered. He didn't think it was safe for me to try. I was in the middle of the purge – my vampire cells were taking over, turning me into a full-vampire, and my body was in a state of flux. But when I pressed him, he admitted there was no real reason for thinking that the purge would have any effect on the procedure. It might even work in our favour – since my vampire cells were hyperactive, they might stand a better chance of destroying the vampaneze cells.

We'd tried to quiz Evanna about the dangers. She could look into the future and tell us whether it would succeed or not. But she refused to be drawn. "This has nothing to do with me," she'd said. "I will not comment on it."

"But it must be safe," I'd pressed, hoping for reassurance. "We're destined to meet Steve again. We can't do that if I die."

"Your final encounter with Steve Leonard is by no means set in stone," she'd replied. "If you die beforehand, he will become the Lord of the Shadows by default and the war will swing the way of the vampaneze. Do not think you are immune to danger because of your destiny, Darren – you can and perhaps will die if you attempt this."

But Darius was my nephew. Vancha didn't approve – he would have preferred to overlook Darius for the time being, and focus on Steve – but I couldn't leave the boy this way, with such a threat hanging over him. If I could save him, I must.

We could have handled the blood transfer with syringes, but Darius insisted on the traditional fingertips method. He was excited, despite the danger, and wanted to do it the old way. "If I'm going to be a vampire, I want to be a real one," he growled. "I don't want to hide my marks. It's all or nothing."

"But it'll be painful," I warned him.

"I don't care," he sniffed.

Annie's doubts remained, burin the end she agreed to the plan. She might not have if Darius had wavered, but he stuck to his guns with grim determination. I hated to admit it – and I didn't say it out loud – but he had his father's sense of commitment. Steve was insanely evil, but he always did what he set out to do, and nothing could change his mind once he'd made it up. Darius was the same.

"I can't believe this is happening," Annie sighed as I sat opposite Darius and prepared to drive my nails into the tips of his fingers. "Earlier tonight I was only thinking about doing the shopping tomorrow, and being here to let Darius in when he got home from school. Then my brother walks back into my life and tells me he's a vampire! And now, as I'm just getting used to that, I might lose him as swiftly as I found him – and my son too!"

She almost called it off then, but Alice stepped up behind her and said softly, "Would you rather lose him when he's human, or when he's a killer like his father?" It was a cruel thing to say, but it steadied Annie's nerves and reminded her of what was at stake. Trembling fiercely, weeping quietly, she stepped away and let me proceed.

Without any warning, I dug my nails into the soft flesh at the tips of Darius's fingers. He yelped painfully and jerked back in his chair. "Don't," I said as he raised his fingers to his mouth to suck them. "Let them bleed."

Darius lowered his hands. Gritting my teeth, I dug my right-hand nails into my left-hand fingertips, then did it the other way round. Blood welled up from ten fleshy springs. I pressed my fingers against Darius's and held them there while my blood flowed into his body, and his into mine.

We remained locked for twenty seconds… thirty… more. I could feel the vampaneze cells as soon as his blood entered my veins, itching, burning, sizzling. I ignored the pain. I could see that Darius was also aware of the change, and that it was hurting him more than me. I pressed closer against him, so it was impossible for him to break away.

Vancha stood guard, observing us, calculating. When he thought the time was right, he grabbed my arms and pulled my hands away. I gasped out loud, stood, half smiled, then fell to the floor, writhing in agony. I hadn't expected the cells to kick in so soon, and was unprepared for the brutal speed of the reaction.

During my convulsions, I saw Darius twisting sharply in his chair, eyes bulging, making choking noises, arms and legs thrashing wildly. Annie hurried towards him but Vancha knocked her aside. "Don't interfere!" he barked. "Nature must take its course. We can't get in its way."

For several minutes I jackknifed wildly on the floor. It felt like I was on fire inside my skin. I'd experienced blinding headaches and loads of discomfort during the purge, but this took me to new heights of pain. Pressure built at the back of my eyes, as though my brain was going to bulge out through my eye sockets. I dug the heels of my hands hard into my eyes, then into the sides of my head. I don't know if I was roaring or wheezing – I could hear nothing.

I vomited, then dry-heaved. I crashed into something hard – the TV I rolled away from it and smashed into a wall. I dug my nails into the plaster and brick, trying to make the pain go away.

Finally the pressure subsided. My limbs relaxed. I stopped dry-heaving. Sight and sound returned, though my fierce headache remained. I looked around, dazed. Vancha was crouching over me, wiping my face clean, smiling. "You've come through it," he said. "You'll be OK – with the luck of the vampires."

"Darius?" I gasped.

Vancha raised my head and pointed. Darius was lying on the couch, eyes closed, perfectly still, Annie and Alice kneeling beside him. Evanna sat in a corner, head bowed. For a horrifying moment I thought Darius was dead. Then I saw his chest lift softly and fall, and I knew he was just asleep.