The sweetness of a hard-won victory lasts all of two seconds. Maybe three. Then it hits me-the rocks within and around the crack are still pulsing. The lights are flashing more vibrantly than at a disco. The wind is growing stronger.

"Beranabus!" I yell. "Why isn't it stopping?"

"It is," he mutters, staring at the crack doubtfully. "It must be. We killed her. But sometimes it can take a minute for a body to properly die, for all the senses to expire. When the last spark of life flickers out in her, this will end."

"But if the demons cross before that..." Beranabus shrugs, then winces and reaches back to try and heal the wounded flesh between his shoulder blades. His skin and eyes are normal now. He looks like a tired old man, not a mighty magician. "A few might squeeze through, but not many. We'll just have to-"

"Imbeciles," Lord Loss snorts. He glares at Beranabus, then Dervish, who's lying close by Juni. Her face has lost its glamour, changed back to its real appearance, scarred and bloody from the beating she took. Dervish is staring at her with a mix of horror and loss. "You think you have defeated us? You believe we fall that easily? You are arrogant and ignorant, Beranabus, the result of too many soft victories over lesser demons. Killing Juni won't save your pitiful excuse of a world-or your lives. It only makes me more determined to see you and the grotesque Gradys suffer slowly and agonisingly."

"We were wrong!" I roar. "The key wasn't Juni. It's one of the demons." I spin, trying to figure out whether it's Artery or Spine.

"It can't be," Beranabus pants, struggling to his feet. "It doesn't work that way, and we saw them both in the future."

"Then I was right," Lord Loss hisses. "You travelled back in time!" He stares at Beranabus, awestruck. "How did you do it? I thought that, of all things, was impossible. How-"

"Beranabus," I interrupt. "We have to kill them now, before the Demonata-"

"But it's not them," he insists. "We saw them."

"Then somebody else!" I holler. "Another human assistant, invisible, hidden by magic. We have to find him... her... whatever!"

Beranabus nods and stumbles away, feverishly scouring the cave with magic and his eyes. I start off in the opposite direction.

"Grubbs," Bill-E moans, crawling towards me, wind snapping at him, clothes and hair rippling, the crack threatening to suck him in.

"Not now. Dervish." My uncle doesn't respond. "Dervish!" I yell. He blinks and looks up. "The key's still alive. It wasn't Juni. We have to find the person who made the sacrifice. If we don't, the tunnel will-"

"Grubbs," Bill-E moans again.

"Stop bugging me!" I scream, then stoop to look him in the eyes. "I'm sorry but there isn't time. If we don't find the person who made the sacrifice, they'll merge with the rock and the demons will flood through and kill us all."

I stand. Bill-E clutches the sodden, straggly left leg of my makeshift trousers. I curse and kick his hand away. I'm turning to continue searching when he whispers something, too soft for me to decipher. I almost don't pause, but there's an urgency in the whisper that demands attention.

"What did you say?" I shout without looking down, eyes piercing the shadows of the cave. It's difficult to see. The lights inside the crack are throbbing more brightly, changing colour swiftly. Bill-E repeats himself, but again too softly for the words to carry. "Speak up, damn it. I don't have time for-"

"I think the key might be me," Bill-E croaks.

And for the second time within the space of an hour the world appears to stop.

Staring at Bill-E. Certain I heard him wrong. Praying that if I heard him right, I misunderstood. "What?" I wheeze.

"I think... it wasn't intentional... I'm not sure... but..."

He wasn't one of the dead, a voice inside my head murmurs. In the future, when you looked into the hole, you didn't see Bill-E. Dervish was there, Reni, most of the other people you cared about. But not your brother.

"Oh dear," Lord Loss snickers, floating out of reach, expression twisting with malicious joy. "The penny drops at long, painful last."

"No," I gasp, the syllable whipped from my lips by the wind. "It can't be."

"Grubbs?" Dervish asks, seeing something fearful in my face.

"Grubbs!" Beranabus roars. He's a long way off. Doesn't know what's going on. "Make yourself busy, boy. We have to find the killer. There isn't much time left."

"But you've already found him, haven't you, Grubitsch?" Lord Loss teases.

"You're lying," I snarl.

Lord Loss shakes his head. "I never lie."

Bill-E falls flat on his stomach and slides towards the crack. Dervish grabs him and holds tight. I crouch beside them, ignoring Lord Loss's laughter and the bite of the demonic wind. I can hear the cries and chitterings of other demons, coming from a universe that isn't our own. I tune them out and focus on Bill-E. He's utterly terrified. I smile at him and even though the smile's weak, he finds comfort in it, and in spite of his terror, he speaks.

"It was Loch," he mutters. "I hated the way he teased me, always making me feel small and worthless. He was a bully. You should have stood up to him, Grubbs. You're my big brother."

"I didn't want to fight your battles for you." I sense what he's going to tell me and I feel like crying, but tears won't come. I can't let them.

"Always teasing," Bill-E says sourly. "Making fun of me. Any excuse to take a dig. That day when we discovered the cave... you were sick... me and Loch went climbing in search of Lord Sheftree's treasure..."

It seems a lifetime ago. Did we really engage in such playful, innocent games? Was there truly a time when buried treasure seemed important, when a school bully was our only concern? Or did we dream it all?

"I saw a chance to get my own back," Bill-E continues, voice breaking. "We were near the top of the waterfall. He slipped and grabbed hold of a rock. He was clinging on by his fingertips. I stuck my hand out. He snatched for it. But then I... I... I whipped my hand away!"

Bill-E and I lock expressions. We both understand what he means. Dervish doesn't. He never saw Loch doing that very same thing to Bill-E at school, making him look like a fool in front of everybody. He's staring at us as if we're mad.

"I whipped it away," Bill-E says numbly. "Put my thumb on my nose. Said, 'Touch¨¦, sucker!' Stuck my tongue out. I didn't mean for him to fall. I just wanted to have a laugh. But he lost his grip. Fell before I could help him. Hit his head on the ground. His skull cracked open. He..."

Bill-E stops. His face is white. He's trembling. The wind pulls strongly at him-more strongly than at me, Dervish or anybody else in the cave.

"No," I say calmly. "You didn't kill him. It wasn't a sacrifice. You aren't the key." But I know it's not true. Even as I deny it, I know.

"Grubbs," Dervish wheezes. "What are you saying? What does it mean? Are you mad? You think Billy caused this?"

"No," I lie. "Of course not." But putting the pieces together inside my head. The death-not an accident. Loch's blood vanishing into the floor of the cave. I'd forgotten about that, but I remember now, the bare floor, wondering where all the blood had gone. Now I know-sucked up by magic. Taken as sacrificial blood, even though it wasn't intended to be.

Bill-E guilty. By the strictest letter of the law he killed Loch Gossel and the magic in this cave is holding him accountable. I should have suspected sooner. Beranabus kept a tight watch on the cave when he arrived. He couldn't understand how Juni slipped past him and made a sacrifice. Never suspected Bill-E. Took me at my word when I told him we were alone, that Loch died accidentally.

The demons had it easy. No need to slaughter one of their mages, or even enter the cave and risk alerting Beranabus. A sweet deal. The sacrifice had already been made. All Lord Loss and Juni had to do was turn up a few weeks later, chant the correct spells and make sure the killer was present.

Except they didn't know who that was. They thought it was me, that the beast or my magic made me murder. That's why Juni sent me to the cave the night I turned, why she took my blood and smeared the edges of the crack with it. When that failed to produce a reaction, they realised Bill-E must be the guilty one. So Juni hurried over to his house, to haul him in. Nothing personal. It wasn't for revenge. Lord Loss wanted Bill-E solely for business. And he never meant to kill him. He had other plans for the younger Grady brother.

The wind increases. Dervish has to dig his heels in hard to hold Bill-E back. He looks at me, panicking. "Grubbs! What can we do?"

That tells me he knows too and understands what must be done. He just doesn't want to admit it, because that would place the burden on him. He doesn't want the responsibility. Well, too bad-I don't want it either.

"Bill-E's the key," I tell him.

"No," Dervish protests, but weakly, unconvincingly.

"Grubbs!" Beranabus yells. "I hear them coming. What the hell are-"

"Bill-E's the key!" I scream and Beranabus gawps at me. "He made the sacrifice. He didn't mean to. It was an accident. But-"

"You don't know what you're saying," Dervish hisses.

I look at him miserably. "Yes I do."

"What's wrong?" Bill-E mutters, glancing from one of us to the other. "This is good, isn't it? Now that we know, we can cast a spell to stop it, can't we? Or... should I have kept my big mouth... shut?"

"No," I smile. "You did the right thing. Everything will be OK now. We can stop the demons. You're a hero. You've shown us the way to win."

Bill-E beams proudly. Dervish is staring at me awfully, trembling, gripping his chubby nephew tight. I turn hopelessly to Beranabus, maintaining the smile until I'm facing away from Bill-E, so he can't see the anguish in my eyes. "Is there another way?" I cry.

"No," Beranabus says, no pity in his voice, just determination. He starts across the cave, fingers flexing. But he's taken no more than three or four steps when Lord Loss drops into his path and fires a bolt of magic at him, forcing him back.

"No, no, no, Beranabus," the demon master coos. "I won't allow you to spoil such a fascinating scene. This is tremendous sport. Uncle and brother speared on the horns of a most gruelling dilemma. What excruciating entertainment!"

Beranabus tries to respond with a magic bolt of his own, but Lord Loss hits him first. The magician collapses, defences crumbling, all washed up.

The wind is a storm now. Bill-E's feet are rising into the air. Dervish won't be able to hold him much longer. Another minute, maybe less, then Bill-E will be torn into the crack, his flesh will join with the rock and he'll become a living tunnel between this universe and the Demonata's.

"Dervish!" I scream.

"I can't."

"But the demons..."

"I know. But I can't." He pulls Bill-E to his chest and wraps both arms around him, fighting the storm, tears coursing down his cheeks.

"Grubbs," Bill-E grunts, jerking his head clear. "What's happening? What do we have to do?"

"Dervish," I say steadily, ignoring the question. "If you don't, we'll all die. Everybody else too. Including Bill-E. We can't save him."

"You do it then," Dervish challenges me.

"No. He's my brother."

"Do what?" Bill-E howls as Dervish and I glare at one another.

Then the fingers of Dervish's right hand creep up Bill-E's back. They stop at his neck and spread, gripping the flesh tight. He hasn't broken eye contact with me. I'm crying, unable to hold back the tears any longer. Bill-E doesn't know what's happening. He looks at me, forehead creased, trying to make sense of this. I hope he doesn't. Better if he never knows, if Dervish does it quickly and it comes as a short, sharp surprise.

His right hand in place, Dervish moves his left hand up. I don't know if he means to choke Bill-E or snap his neck. And I never find out. Because the fingers halt halfway up Bill-E's spine.

"I can't," Dervish says quietly, and this time the words are the confession of a broken man.

"I knew it," Lord Loss laughs. "Humans are so predictable. Even though all else must fall, you cannot bring yourself to harm your beloved nephew. You'll damn yourself, him, the whole world, all because of misplaced love." He sighs happily. "Moments such as these make the long, monotonous millennia worthwhile."

Dervish moans and clutches Bill-E close, planning to hug him as long as he can, to maybe get sucked into the crack with him, so the pair can perish together. Except Bill-E won't die. He'll become something terrible and twisted, inhuman and beastlike.

I think of Bill-E suffering, captive within the rock, alive down here indefinitely, wracked with guilt, a plaything for the Demonata when all the other humans have been slaughtered. They'll torment him. Guilt will eat him whole. Madness will be his only escape, but the demon masters will use magic to restore his senses, to torture him afresh. An eternity of misery, madness and sorrow.

I can't let that happen.

Entering this cave, I realised I couldn't kill Dervish or Bill-E if they were in league with Lord loss, not even to save the world. I still can't. But to save Bill-E from a fate genuinely worse than death... for my brother's sake, as opposed to the sake of billions of others who mean nothing to me...

"Bill-E." I lean forward, smiling. "Want to help me kick the crap out of these demon creeps?"

Bill-E returns the smile. "Now you're talking! What do we have to do?"

"Grubbs," Dervish groans.

"Shut up," I snap, then smile at Bill-E again. "Take my hands, little brother. Close your eyes. Focus on..." I gulp. "Your mum. Think of your mother."

"How can that help?" he asks doubtfully.

"It'll clear your head of bad thoughts and fear," I improvise. "I need your help to stop this. But I can only do it if you're calm. It won't be easy, but you have to try. Think of your mum and every good time you ever shared. That will generate a positive energy which I can channel. I can use that power to stop the demons."

"Brilliant!" Bill-E gasps, face lighting up. He sticks his hands out, shuts his eyes and concentrates, lids twitching, eyeballs rolling behind them as he searches his memories for cherished moments. He trusts me completely.

Lord Loss has drifted closer. He could stop this, kill or delay me, but he's entranced. He's forgotten his mission of all-conquering mayhem. Living only for the bittersweet pain of the moment. Dervish has lowered his face to Bill-E's shoulder, diverting his gaze. I can't see Beranabus, Kernel, Spine or Artery. I don't care. There's only Bill-E and me in the world now. We're all that matters.

I let magic build within me, then reach out to take Bill-E's hands. I stop. A moment of doubt and disbelief. I can't do this! Then I look over Bill-E's head. I see claws coming out of the crack. A massive, shadowy cloud of a face, pure evil. Every shade of darkness imaginable. It fills the gap entirely. I'm not sure what it is-no ordinary demon, that's for sure-but I know it exists only to destroy, and will unless it's stopped.

"I love you, Bill-E," I whisper, my heart breaking. And take his hands.

Magic flows from me into my brother. Soft, warm, pleasing energy. His smile spreads slowly from the warmth of the magic or an especially fond memory.

Maybe both. The face of shadows within the crack splits with hatred. It hisses-the sound of a sea boiling dry. Tendrils of darkness dart towards me, a thousand writhing snakes, intent on tearing me away from my brother, separating us forever, using Bill-E for their own evil ends.

"Time to fly, little brother," I sob, and quickly push. The energy touches Bill-E's heart and stops it instantly. No pain. Bill-E's smile freezes in place. The tendrils of darkness blow apart. A furious, hateful bellow as the shadowy face disintegrates. Screams within the crack from scores of cheated demons. The wind stops dead and the howl is replaced by the noise of rocks grinding together as the crack closes. The screams rise sharply, then die away.

It's over.

I lean forward. Put my lips to my dead brother's forehead and kiss him, my tears dropping on to his still warm flesh. Then I hug him and Dervish tight, and pray for Lord Loss to kill me swiftly, before I lose my mind to wretched, soul-destroying grief.