Run Fast joins us nearly an hour later. I thought he'd be quicker than that, and was worrying, thinking about going back for him. When he appears, I see why he was so long-he stopped to pick flowers and weave a necklace out of them.

"Turnips!" he shouts happily, waving the necklace at us.

There's a big group cheer and we surround him, laughing, hugging, exclaiming at the same time-

"That was amazing!"

"I've never seen anything like it!"

"You must be a son of the gods!"

"The demons thought they had us dead but they didn't count on Run Fast!"

Run Fast smiles hazily, unsure of what all the fuss is about. In his head, I don't think leading demons a merry chase counts for much. He's far prouder of the necklace of flowers.

When we're through congratulating Run Fast we set off again, anxious to cover as much ground as we can before nightfall. It's a showery day and we're soon soaked. But that's a minor inconvenience. We'll take any amount of soakings after our unexpected escape from the demons.

Early afternoon. I've been discussing the ring of stones with Fiachna, wondering how old it was, who built it, what its original purpose might have been.

"A pity they didn't have ogham stones back then," Fiachna says. "They could have told us who they were and lived on through their writing."

"Can you read ogham?" I ask.

"A bit. I learnt it from a bard who couldn't pay me for my work. Can you?"

"No. Banba didn't like ogham. She said magic shouldn't be recorded, that history should be kept alive by word of mouth."

"Perhaps," Fiachna says. "But many stories are lost forever that way. I think..." He stops, eyes narrowing. "Connla!" he calls-the young would-be king has been leading for the last couple of hours. When Connla looks back, Fiachna points to a spot off to the right. "A large, strange hut. I think it's a church."

Everyone gathers around us. I can see the tip of the building now that Fiachna's pointed it out. It's not like any I've seen before but I've heard of its type. A Christian church. I didn't know they'd built any this close to our tuath.

We advance on the church. My insides are tight. It's a feeling I always get when I hear of the upstart religion.

Christians are new to our land, but already it's hard to imagine a time when they weren't here. They've spread as fast as rabbits, bringing their churches and unnatural ways into tuath after tuath, converting everyone they encounter. I've never met a Christian but from what I've heard they're powerful and persuasive, with no tolerance for other ways of thinking. They believe all people should follow their faith, that no gods are real except their own.

The threat of Christians was a major worry for us before the Fomorii came. Even though we were far removed from any of the infected tuatha, we knew we couldn't hope to avoid them forever.

From what we heard, they'd converted all of the north and east. It was only a matter of time before their priests came-maybe their high priest, Padraig, would come himself-and then...

Would they convert us too? Would Conn grant them his backing, as so many other kings had, and order us to follow their ways, abandon our gods, adopt their customs? It didn't seem possible. Our religion is old. Our gods are sacred, as real to us as our ancestors. We lead our lives based on ancient, just laws, handed down from father to son, mother to daughter. How could we turn away from all that within a matter of days and become another people entirely?

I'd have said it was impossible, except I knew from the reports that it isn't. While the Christians don't have our understanding and control of magic, they have strange powers of their own. They've come from far across the world, winning over most of those they met along the way. Common sense suggested we'd be no different, no more immune to their persuasive spells than any other clan.

We thought Christianity was the worst disaster that could befall us. Then the demons attacked and we realised there were far greater enemies in the world than the followers of the god they call Christ.

Creeping up to the door of the church. I sense power within. A dark, throbbing, painful power. It gives me a headache. This church doesn't have the natural feel of our own holy places. It's a building of power but not magic.

We stop at the door of the church, unwilling to enter in case demons are inside. I thought a church would be protected from the Fomorii, like the ring of stones. But as powerful as they are, Christians lack the skills of the Old Creatures, because it's obvious this church has been attacked and demons have been at play.

We can see the mess through the open door. Blood everywhere. Bits of human bodies. A man's head-maybe a priest's-stuck on the tip of a spear set in the centre of the church. Eyelids ripped off, eyes gouged out, demonic symbols scrawled in blood across his forehead and cheeks.

"I've never seen demons do this," Goll says, scratching the flesh over his own lost eye. "They usually strike and kill, make off with the bodies they want, leave the others just scattered around. This is different."

"It's like what we do with our enemies after a battle," Fiachna agrees. "If you add this to the trap they built around the ring of stones, there's only one conclusion. Tiernan was right-they're becoming more intelligent."

I feel sick when Fiachna says that. If the demons start plotting, scheming and fighting like humans, with their extra strength and powers they're certain to crush us all within months.

We stand in the doorway a few moments more, studying the face of the dead man. Then we retreat, spirits dampened, and continue on our trek to Run Fast's home, wondering if we'll find similar scenes of chaos there.

Late in the evening. Worrying about the night ahead and where we'll stop. It's too much to hope to find another ring of magical stones. We're tired from the march and lack of sleep. If we don't find shelter soon, we're in trouble.

All of a sudden, without warning, Run Fast darts ahead of us. He stops, looks back and beckons hastily. "Bumpy frogs!" he shouts. "Run fast!" Then he tears ahead, disappearing through the trees.

"Looks like our journey's at an end," Connla smiles. "I thought we'd have a much further march than that."

"The gods must be looking down on us," Goll grunts, then catches Connla's arm as he goes to follow Run Fast. "Careful. Don't forget why we're here. These people are in trouble. There's no telling what we'll find. The demons might have them surrounded, like at the ring of stones."

Connla hesitates, then takes a step back. "What do you suggest? Go in together or send a scout first?"

"Together," Goll says after a second of thought. "To separate is to weaken. But everybody draw your weapons and tread carefully."

When we're all prepared, we advance cautiously, scanning the branches of the trees overhead and roots at our feet-sometimes worm-like demons disguise themselves as roots and snag unsuspecting passers-by.

A couple of minutes later we come to a clearing and find ourselves at the edge of a lake. A crannog has been built on an island in the middle of the water. A small, fenced fort, containing half a dozen huts. There's a sentry post built above the gate, and from the marks beneath it and here on the shore, I think there was once a bridge connecting the island to the mainland. But that's been demolished, probably because of the threat posed by demons. Now you can only get to it by swimming or in one of the curraghs tied up close to the fort's gate.

"Hello!" Goll yells. Echoes, then silence.

Run Fast is hopping up and down, his face alight, reaching out to the crannog as though he can stretch across the lake and stroke the walls of the fence.

"Anybody there?" Goll shouts. When the silence holds, he adds, "We've come to help. Your boy told us you were in trouble. We're here to..."

He draws to a halt, since it's obvious nobody's going to answer.

"It's a ghost village," Ronan says.

"We're too late," Connla sniffs.

"Maybe not," Fiachna disagrees. "They might be sheltering underground, in a souterrain, where they can't hear us."

"You two seem to think people do nothing but cower underground," Connla snorts, nodding at Fiachna and Orna. "Why don't you just accept the simple truth that when nobody answers a call, it means they're all dead?"

"I prefer to hope for the best," Orna says stiffly, "even when I can see just as clearly as you that it's unlikely."

"Smoke bread," Run Fast says bafflingly, leaning over so far that he almost topples into the lake.

"Right," Goll says. "We haven't come all this way to turn back now. If nothing else, the crannog offers a place to rest tonight."

"Unless it's been taken over by demons," Connla says.

"Unless it's been taken over by demons," Goll agrees. "But we have to check. Lorcan, will you swim across and come back in a curragh for the rest of us?"

Lorcan's the best swimmer in our tuath. Even when he was twelve years old, he could beat most grown men in a race. He steps forward now and studies the water, looking for demons. He can't see any but that doesn't mean it's safe-they often hide down deep during the day, to avoid the rays of the sun.

Without saying anything, Lorcan undresses quickly, then dives in and strikes powerfully for the crannog. We watch nervously, Ronan having notched an arrow to his bow, ready to fire instantly if his brother comes under attack.

Lorcan makes it to the crannog unhindered and pulls himself out, pausing only to offer up a quick prayer of thanks to the gods. He brushes water from his stubbly hair-it comes off in rusty red drops, coloured by the blood caked into his scalp. Then he unties a leather-framed curragh and rows across to where we're waiting, hard strokes, one eye on the setting sun.

Lorcan, Goll, Run Fast and Orna cross first. Then Lorcan rows back to pick up Ronan, Fiachna, Connla and me. At the gate I test the air for the scent of demons. It's clear. I don't think there are monsters in the village but I can't be certain.

"Will we try the gate or go over the fence?" Goll asks.

"The gate's open," Fiachna says.

Goll squints, then chuckles. "I was never the sharpest with two eyes, but with only one..." He looks around. "We'll go in fast. Any sign of trouble, retreat to the gate. Based on what we're facing, we'll decide then whether to fight or flee."

Deep breath. Weapons drawn. A signal from Goll. In.

No demons. No people either. Just a few chickens and lots of blood. While we stand a few paces inside the gate, Run Fast chases after the chickens, laughing. They squawk and flap away from him. With his speed he could catch them easily, but he's only playing with them.

"Do you think they're all dead?" Orna asks, eyes narrow, nose wrinkled against the stench of fresh blood.

"Unless they're hiding," Goll grunts.

"We should check the huts," Fiachna says.

"Aye." Goll points at Ronan, Fiachna, Connla and me. "You four go right. The rest of us will go left. We'll meet in the middle if all's clear."

"What about Run Fast?" I ask.

Goll looks at the boy chasing the chickens. "I don't think he'd be much help."

We set off quickly, each of us aware of the rapidly setting sun. It's almost the time of the Fomorii.

The first hut. Holes have been torn in the walls, so it's easy to peer in. Floor caked in drying blood but otherwise empty. No trapdoor or hiding place. We push on.

The second hut's smaller than the first. A tiny entrance. No holes in the walls. Dark pools of shadows. We stick our heads through the doorway, allowing our eyes to adjust to the gloom. Objects gradually swim into sight. Pots, a small table, a broken chair. Rugs on the floor-there could be a souterrain beneath. We slide in, Ronan first, me last, looking up for winged demons hanging from the thatch. The men search beneath the rugs-nothing. They file out. I'm bringing up the rear, almost through the door, when something breathes behind me.

"Beccccccc..."

I stop... turn... eyes wide... heart beating fast. I stare into the shadows. I can't see anything but I know I'm not alone. I want to duck out of the door or call for help but I can't. My tongue is frozen, not with fear, but magic.

Long, terrifying seconds pass. Then, in a blur, claws dart out of the darkness... a twisted face... fiery eyes... a savage mouth filled with rows of teeth... the demon grabs me!