We move so fast, it's as though we're not really part of the world. The horses push on at tremendous speeds without appearing to tire. It's only when we stop at Drust's command that they sweat and pant, trembling from exhaustion. We rub them down to warm them, find water for the beasts to drink and let them graze for a while. The others are keen to continue but Drust says we mustn't rush the horses.

"I'm keeping a close eye on the time," he snaps, irritated at being questioned. "This is my quest. I'm the one who knows what we can and can't do, when to race and when to rest."

While the horses are grazing, the druid approaches me. "I want you to ride beside me when we remount," he says. "I'm going to teach you the spells needed to close the tunnel."

"Why? I thought you were going to cast them."

"I am. But if anything should happen to me..."

"The Old Creatures said it would only work if a magician or priestess was sacrificed."

Drust sighs. "Aye. But if the worst comes to the worst, you might as well try it on one of the others. Cast the spell-it's complicated but I think you'll be able to master it-then pick someone for sacrifice..." He hesitates, gaze flickering over my friends. It comes to rest on Bran.

"No," I say instantly.

"He's a kind of magician," Drust says. "Of the four, he'd be most suitable. You'd stand a better chance with him than-"

"No," I say again. "Goll or Lorcan would give their lives willingly-maybe even Connla, though I doubt it-but Bran wouldn't understand. He couldn't make a choice. I won't kill someone who doesn't know what's being asked of him."

"I'm not so sure he wouldn't understand," Drust murmurs. "But if he didn't, wouldn't that be for the best? You could do it quickly, mercifully. He needn't even know what's happening."

I shake my head stubbornly. "If I have to, I'll ask one of the others. But I won't murder Bran."

"Even knowing the consequences if we fail?" Drust asks menacingly.

"Even then," I mutter. "There are certain things we should never do. Otherwise we'll become like the demons-mere monsters, best suited to the dark."

Drust shrugs sourly. "As you wish. If luck is with us, it won't come to that. But I thought I'd make you aware of your options. Just in case."

He rises and shouts at Bran to gather the horses-though they obey us when we're on their backs, they revert to creatures of the wild when left to graze and only Bran can get close to them. Soon we're off, racing through a forest, Drust riding beside me, teaching me the spells which will hopefully destroy the tunnel between this world and the Demonata's.

We rest several times over the course of the day. The third time, one of the horses collapses and dies. I ride with Bran after that, my hands loose around his waist. I can tell he enjoys having me behind him by the way he tilts his head back to nuzzle my cheek.

We stop for nightfall. This time Lorcan and Goll don't question Drust's judgement, but it's plain from their worried expressions that they think we should press on. Drust sees this, and though he scowls, he takes the time to reassure them. "We made excellent progress today. If we rest the horses tonight, we can push them hard tomorrow and arrive at the tunnel by afternoon. If we continued now, they'd die before dawn, leaving us to walk-we wouldn't make it on time."

Many demons pass us during the night, snuffling and snorting, more than I've ever seen before. It must be because we're so close to the tunnel through which they cross. It's hard masking the horses from the demons, but Bran gathered them in a small circle before dusk and dozes in the middle of them, waking whenever one stirs, shushing them, keeping them motionless.

I don't sleep. I can't. This is probably my last night alive. It's horrible, lying here, shivering with cold and fear, knowing what's to come, thinking about death and all that I'll lose. Why couldn't I have fallen in battle, killed quickly, no time to worry about the Otherworld and what I was leaving behind? This waiting is worse than death itself.

I have moments of doubt in the middle of the night, when the world is a lonely place. I could run. Desert with Connla. I'm not sure why he's stuck with us this long. He could have left when we were at the coast or when Bran brought the horses. He said he wasn't one to flee a challenge but maybe it's just that he fears running by himself, with no one to watch his back. If I said I'd go with him, I'm certain he'd jump at the chance. With his strength and standing, allied to my magical abilities, we could be a mighty pair. Set ourselves up as rulers of some far-off tuath. Connla a king, me a priestess-queen. All-powerful.

It's tempting. I know my duty and I believe my suffering will be brief, that I'll find peace in the Otherworld. But in my heart I'm a young girl, afraid of the darkness of death, wanting to grow up and see more of the world, taste more of life. I cry quietly to myself, thinking of the terrible sacrifice I must make, the joys I will never know, the love I'll now definitely never find. Part of me wants to slither across to Connla, put my offer to him, then leap on a horse and ride out of this nightmare as fast as I can.

But I don't. Duty wins out over fear in the end. I can't stop the shivers or the fast beat of my heart, but I can wipe away tears and hold my ground. And I do. I hate the prospect of dying and I'm more afraid than I ever thought I could be. But if this is my destiny... if it's what the gods ask of me... so be it. Better to die for my people in my own land than rule in another and suffer a lifetime of cowardly guilt.

Many of the demons return in the hour before dawn, some bearing trophies of their battles with humans-heads, limbs, torsos, sometimes children who are still alive, kicking and screaming in terror. It's hard to ignore the cries of the young but there's nothing we can do without giving our position away. If we did that, the demons would attack in great and unmerciful force and we'd all perish.

"They'll be the last," Drust whispers, his eyes hard. "After tomorrow, no more will die at the hands of the Demonata."

"You promise?" I ask, my fears and doubts causing me to question him, desperately searching his face for a hint of the lie that would provide me with an excuse to bail out.

"I promise," Drust says calmly. "It won't be easy, but having come this far I'm sure we won't fail." He pauses. "You're still prepared to...?"

"Of course!" I snap, pretending to be offended by the notion that I might have had second thoughts.

He lays a gentle hand on my right knee. "It will be quick. It won't hurt. You have my word."

I shrug as if that was the furthest thing from my thoughts, then listen to the demons crashing by and try to drown out the echoes of the children's screams.

Day. The order of the world restored. My final sun. Fittingly, it's obscured by heavy grey clouds. I've heard that clouds are rare in some lands, that the sun shines all day in a clear blue sky. But surely those are fanciful tales, told for the amusement of the young. This world was made to be cloaked in grey. It wouldn't feel natural if the sun shone brightly all the time.

Drust examines the horses and declares one of them unfit for the trek. We let it go and after a few mumbles from Bran it wanders off to find a good grazing spot. Perhaps it will be the only survivor of our group this day.

Before we leave, Drust makes a final speech, looking around slowly, his gaze lingering on each of us in turn, first Connla, then Lorcan, Goll, Bran and me.

"I've acted as if I don't care about you. In the beginning it was true. You were figures for me to manipulate, like pieces on my chess board. I didn't care if you lived or died. I couldn't afford to.

"But I've changed. I wasn't aware of it happening but it did. I think of you as friends now. You've been loyal and brave, putting the welfare of others before your own, risking all on the strength of my promise to rid this world of demons.

"So I say to you now, as friends-you can leave. Only Bec and I need go on. If our plan works, there won't be any battle. If something goes wrong and we have to fight, the chances are you won't make much difference against the masses of demons. You can step aside and return home without any shame or guilt."

He stops and awaits the men's response.

"A gracious offer," Goll says warmly, "but I'll stay. I want to see how it finishes, so I can tell those in our tuath and bask in the glory. I've always wanted to be part of a legend!"

"Me too," Lorcan says. "Besides, I want to kill a few more demons before you banish them from our land. For Ronan."

We all look at Connla. "I'm going nowhere," he says quietly, defiantly.

Drust smiles. "True warriors one and all." He puts a hand out and, one by one, we touch it, until all of us are joined, even Bran, who squints at the hands as if he expects a trick. "To the end," Drust says simply.

"To the end," we repeat.

"Of the demons!" Goll adds and we laugh.

Then we mount up-Drust rides with Bran, while I sit behind Lorcan-and set off. Our final journey. Our final challenge. My final day.

Working on the spells of closure. Not one spell but several. Spells to join split rock back together, move earth, seal magical gaps. The most difficult spells I've ever tried to learn. Even with my vastly expanded powers I have trouble mastering them. My tongue trips on the words. Despite my perfect memory, I get the order wrong and muddle them up.

Drust doesn't lose his temper. He repeats the spells over and over, making me slowly practise the words and phrases which are particularly difficult.

"This is helpful for me too," he says as we take a short break. "I've never cast these spells before. It's good that I get the order straight within my mind and the words clear on my tongue."

"If you... if I have to replace you," I say. "When do I make the sacrifice?"

"You'll know when the time comes," he says. "The spells will direct you. There is no single right moment. These spells react to the threat which the caster faces, so they're different each time. Even as you're uttering them, they'll change. As long as you keep the original spells clear within your thoughts, and don't stumble, you'll be fine-the new spells will carry you along."

"And if I make a mistake? Should I stop and start again?"

"No," he says quickly. "Once you start, you must continue. If you say a wrong word or stutter, don't stop. Push on and hope the error wasn't important. There will be forces working in opposition to our magic. Once the Demonata realise what we're doing, they'll set themselves against us. The spells will protect us-I hope-but if they break down, a second is all it will take for our enemies to destroy us."

I wish he could be more encouraging, but this is a time for the truth, however troubling it might be. So I listen. And repeat. And hope that I'm never charged with the task of having to do this. Because I'm not only unsure whether or not I'd be able to get the spells right-I also don't know if I could bring myself to take up a weapon against one of my friends and kill him.