The walls of the tunnel are hot and fleshy, both to the look and touch. By the glow coming from Drust's hands I can see more of Brude from here-more than I want to. Almost all the bits inside him-the bits of a person which are supposed to remain hidden-are obscenely revealed, pulsing, bubbling and gurgling within the transformed layers of rock.

Brude screams at us as we invade the tunnel of his body, his voice only just audible above the bellowing and mewling of the demons. He curses us, threatens a violent end, warns us to turn back. When that fails, he tries to win us over with promises of power, long lives and protection from the Demonata.

We ignore him and proceed, Drust chanting words of powerful magic, me following obediently, awaiting his command.

Brude's voice fades as we move down the tunnel until it's nothing more than a low murmur. The walls around us change too, hardening, becoming more like real rock, although with small lines running through them-I think they're veins.

I expect Drust to stop, complete his spells and make the sacrifice. But he keeps moving, slow but sure, following the path of the tunnel as it curves and dips ever lower. I want to ask why he doesn't end it here, so he can get out quickly if successful, before the walls close around him. But I dare not interrupt while he's casting the spells, for fear I'd break his concentration, shatter the web of magic and free the demons to hurtle down the tunnel after us.

Eventually, the tunnel leads us to another cave. This one's smaller than the first, with none of the spectacular formations. Most of the floor is covered by a pool of water. An island of bones juts out of the middle of the pool. In the centre stands a large rectangular stone which reminds me of the ring of Old stones where we sought shelter from the demons.

Drust stands by the edge of the water, observing the stone, for several minutes, muttering more spells. Then he stops and looks at me, smiling tiredly. "A lodestone," he says. "A reservoir of ancient magic. Very powerful. We think the Old Creatures used stones like this to mark the position of our world, so they could find their way here from the stars. The Old Creatures have drained most of the remaining lodestones of their power, but they either missed this one or deliberately left it charged for one reason or another. Brude found it and used it to open the tunnel. We'll turn it against him now."

"Is it safe for you to stop?" I ask nervously, glancing back up the tunnel.

"For a moment," Drust says. "The spells I've cast are at work on the walls of the rock, Brude, the..." He nods towards a point beyond the island. Staring hard, I see the mouth of a second tunnel in the rock on the far side of the pool-but the walls of this tunnel are made of red webs and strips of flesh.

"That's the tunnel to the Demonata's world?" I ask.

"Aye. On their side a demon master has undergone a transformation like Brude, creating that tunnel. The lodestone links the pair. It's been absorbing magic from Brude and the demon master, uniting their forms, slowly knitting together the fabric of the two tunnels. The lesser demons have been able to squeeze through during the process. When the tunnels become one, the masters will be able to follow their servants to our world. If that happens, mankind is finished."

"What if a demon comes through when you're casting the rest of your spells?" I ask.

Drust pauses. "I won't be able to stop. You'll have to fight it." He runs an eye over me. "Are you all right?"

"Yes." I lick my lips, mouth dry from the heat of the tunnel and cave. "Goll and Lorcan are dead. Connla too. I removed his protective spell. The demons killed him."

"Good," Drust grunts. "And Bran?"

"I don't know. He was alive when we entered the tunnel, but there were so many demons..."

"If I make it back, I'll look for the boy," Drust promises. "If he's alive, I'll take care of him."

He straightens, casts his tiredness off and steps into the water, starting on the next set of spells. I stare at the island of bones for a second-impossible to tell if they're human or demon, or a mix of the two-then step in after him. Despite the heat of the cave, the water's cold, but not as cold as the sea was. No need for a warming spell. I wade after Drust, eyes on the lodestone and bones, morbidly wondering if he'll leave my bones there, on top of the pile, when he's done.

The water's shallow, no higher than my lower thigh. It doesn't take us long to reach the island. When we're there, Drust climbs up on to the mound of bones. The bones are brittle and many snap under his feet. He takes no notice, continues with the spells, clambering his way over to the lodestone, beckoning me to follow.

The glow in Drust's hands has changed from blue to a pinkish red. The bones-especially the skulls-look as though they're aflame. I try to keep my eyes off them as I crawl to where Drust is kneeling, hands stretched out on either side of the lodestone, ready to clasp it when the moment's right.

As Drust casts spells, I move slightly to one side of him, so I have a clear view of the tunnel to the Demonata's universe-I want plenty of warning if a demon comes through. But the monsters on the other side don't seem to be aware of the threat, or else they can't cross quickly. Nothing stirs. No shadows or sounds.

I find myself thinking about the bones and lodestone. Who set them here? The stone was put in place by the Old Creatures, but did Brude stick the bones underneath it? Have they been left by demons? Or are they the work of the Old Creatures too? Did they sacrifice people to create this place of magic, as Drust plans to sacrifice me?

Despite my unease, I can't help studying the skulls, wondering if these people were killed on the surface or if they died down here. Were they volunteers? What were they thinking in their final moments? Did they go bravely to their deaths, as I hope to, or did they crumble at the end and scream for mercy?

Drust's voice rises, disturbing my thoughts. His hands close upon the lodestone, drawing gradually closer as he slips deeper inside the intricate web of spells. I listen to his words, and though they're hard to decipher-he's speaking so quickly!-after a while I catch a few of them. He's on one of the final spells. It won't be much longer. If I want to offer up any last prayers for myself, I'd better do so now, before-

Drust cries out. His hands fly wide apart, then dart to the small of his back. My eyes shoot down and I spot a dagger sticking out of his flesh, handle quivering, buried to the hilt. I whirl, summoning magic, expecting Connla or a demon.

But it's neither.

It's Bran!

The boy stands at the edge of the pool, arm extended-he threw the knife. His face is curiously blank.

My heart leaps. Has Bran's innocence been an act all along? A spy in our midst, playing us for fools, waiting for the ultimate moment to strike? Impossible! Nobody could have been that convincing an actor. But there he stands, hand outstretched, dagger buried in Drust's back.

Drust topples aside and sees Bran. He yells with astonishment, then groans with pain. I falter. I want to unleash a spell, drive the boy-the killer-back, destroy him if I can. But it's Bran! I can't hurt him, not until I'm sure, not unless-

"Why?" Drust gasps.

Bran blinks. He frowns at Drust, then looks at me-and bursts into tears. "Flower!" he cries. Starting forward, he wades sluggishly through the water, arms flailing, displaying none of his customary lightness of movement.

"Bec!" Drust croaks. "Stop him!"

"No," I sigh, letting the spell die on my lips, understanding by his tears what has happened. "It's all right. He won't do any more damage."

Bran makes it to the island of bones, wailing and sobbing. He throws himself at me, yelling "Flower!" again and again. I catch him, let him bury his face in my chest, and hold him as he weeps, stroking the back of his head, murmuring quieting words.

After a few seconds I look over his head at the wounded druid. "He heard us on the cliff," I whisper. "He knew you planned to kill me. He couldn't let that happen. In his own crazy way he loves me. He hasn't done this to sabotage your plans-he did it to save me."

Drust grits his teeth with desperate anger. "The idiot! Doesn't he know what will happen if-"

"No," I interrupt calmly. "He doesn't. I'm his friend, maybe the one person in the world he feels close to. He only knew that he didn't want me to die. Don't blame him. He couldn't control himself."

Drust's expression softens. "Aye," he chuckles. "I think you're right. It's not much comfort to us, but..." His eyes flick to the lodestone. He reaches for it, then winces and remains lying on his side. "I can't do it, Bec."

I go cold. "You must!"

He shakes his head. "It's not too late-the spells will work if resumed quickly-but Bran has wounded me deeply. I haven't the strength to continue."

"You must!" I shout again. "You have to try! Don't just lie there and give up!"

"I'm not talking about giving up," he smiles sadly. "I can't complete the spells-but you can."

"And sacrifice Bran?" I ask quietly, dreading the answer.

"No, you fool," the druid snaps, more like the Drust of old. "Why kill two when one's already half dead? I'm finished. Even if I could cast the rest of the spells, I'd never make my way back to the surface. You need to take over, complete the spells, then slit my throat and let my blood flow over the lodestone."

I stare at him stupidly.

"There's no time for gawping," he growls. "I'll last a few more minutes with luck, but not much longer. Do it, Bec. Say the spells. Kill me. Spare your people the wrath of the Demonata. Then save yourself and Bran."

That final word jars me into action. Bran's risked all to rescue me. I can't repay him by stranding him here, to perish at the hands of the demon masters when they come. Unwrapping his arms from around my shivering frame, I push him back, smile to show everything's all right, then shuffle up beside Drust.

"What do I have to do?"

"Do you know where I stopped?" he asks.

"No."

"You must," he insists. "You have a perfect memory. Cast your thoughts back."

It's not easy but I force myself to focus. I pick at the strings of my always reliable memory with nimble fingers. Recall the spell Drust was chanting, the place where Bran interrupted him. "Got it," I mutter.

"Continue from there," the dying druid says. "Spread your arms. Embrace the lodestone as you finish, then launch into the next spell. It should be a clear run from there."

"And the sacrifice?" I ask. "When...?"

"You'll know," he vows.

One deep breath. A quick glance at the tunnel to the Demonata's universe to make sure nothing's barging towards us. I begin.

The words come easily. There's great power in this cave. I sensed it as soon as I came here- even before, when I was on the surface-but it's only when I open myself up to the magic that I feel the full extent of it. This stone has been filled with some of the most potent magical power imaginable. I believe I could do anything I set my mind to if I tapped into the lodestone long enough.

I finish the spell, then grab the stone with both hands. I mean to start the next spell immediately, but the rush of power from the lodestone catches me by surprise and the words stick in my throat. It's incredible, as if all the magic of the stars was rushing into me. I can see the universe, the entire night sky. I could reach out if I wanted, leave this world, go and explore the stars with the Old Creatures. This land suddenly seems insignificant, hardly worth bothering about. With this much power I could create my own worlds and people to inhabit them. Not a priestess, not a queen-a goddess.

Fate whispers to me. Asks me to accept a new destiny, travel a fresh path, blaze a godly trail. I don't ever have to know fear again, pain, want. I don't even have to die. All I need is to reach out and...

"Rainbow," Bran whispers, touching my left forearm, gazing at me seriously.

I feel the power rush into Bran through my flesh, then out of him again. It's not that he can't hold it-he just doesn't want it. The promise of the stars doesn't interest the boy. He cares only for me. If he could express himself with words, I think he'd say something like, "All the power in the universe means nothing if you can't be with the one you love." And he's right. What's the point of becoming a goddess if it costs the lives of all those I care about? I don't want a world of worshipful slaves, just a village of welcoming friends.

I smile at Bran, nodding slowly. He smiles back and releases my arm. I focus, close my eyes, shut out the seductive temptation of the stars and cast the next spell.

A wind develops as I progress, a hot, biting, swirling wind. It gusts in a circle around the island of bones, gathering speed and power. Drust and Bran huddle up to the lodestone, not touching it, but wriggling in as close as they can, sheltering from the unearthly wind.

Screams. At first I think it's the sound of the wind. Then I realise they're coming from the tunnel which links this cave to the realm of the demons. The Demonata know what's happening. They can sense their gateway to this world collapsing. But all they can do in response is shriek hatefully at the herald of their ill fortune.

The spells race off my tongue. I'm barely aware of what I'm saying. I was foolish to worry about making a mistake. The spells are almost chanting themselves. I don't think I could stop even I wanted. I'm not in control now. The magic is.

I draw to the end of another spell, lick my lips, open them wide to start on the next... and stop. It's time. Only one spell left. And that comes after the sacrifice.

Drust knows too. He hauls himself up without having to be told. Smiles crookedly at me. "Live long, Bec. Live well."

I don't answer. I can't. My next words can only be words of magic. I can't break the sequence of spells.

Drust limps around to the other side of the lodestone. He leans forward, so his chin is directly over the rock. Then he tilts his head back, offering his throat. I let go of the lodestone with my right hand and press the nail of my index finger to the flesh of his throat. I smile at him, a tear trickling from my left eye. Then I swipe the magically hardened and sharpened nail across.

Blood gushes. The lodestone is soaked. It absorbs, then thirstily gulps the blood. Drust trembles but doesn't fall away. I can't see his eyes, only his throat. I'm glad of that. He remains upright, feeding his blood to the stone, held up by magic or sheer willpower-I'm not sure which.

And then, as the stone flashes with a blinding yellow light, Drust slumps.

No time to grieve. With a bellow of triumph, I roar the words of the final spell. The lodestone quivers. The cave shakes. The wind howls to a climax, ripping the outer layers of bones off the island, threatening to pick loose Bran and me and dash us to death against the walls. But before it can...

Release.

The wind roars up the tunnel-Brude's tunnel-increasing in strength as it tears through the druid's form. It fills the cave beyond, then explodes up the shaft and billows outwards at an unnatural speed, in all directions, scraping every demon and undead spirit free of the earth. It's like a giant wave, washing away all things demonic in its path, carrying them tumbling and screaming to the very edge of the land, not stopping until it reaches the sea, where it pauses for one long, dreadful moment... then sweeps back, drawn to its source, this point. After that it will drag its demonic prisoners back to their own world and crudely dump them there.

I don't wait for that. Magic has brought understanding. I know that when the last of the demons has been blown back to its own land by the final gust of wind, Brude's rock-infused bones will follow, then the tunnel will close, the rip between worlds will heal-and anyone still here will be crushed by rock or trapped underground to die slowly and horribly in the darkness.