'Do you fear her, Myrddin?'

He watched the fire for a moment before answering. 'I fear her greatly, Gwalchavad,' he said quietly. 'Abandon any hopes you harbour that we shall escape the full impact of her malice. We will not. Morgian has determined the fight, and chosen the battleground that suits her best. The Queen of Air and Darkness will not spare us the least torment or travail. Our journey will be an ordeal of suffering.'

'Yet we go to meet her.'

'We go to meet her,' he replied, 'because we have no other choice.'

Arthur did not join us at the fire that night – his usual custom when we were encamped – but took food in his tent, admitted no one save Rhys, who served him, and emerged only at dawn the next morning when we moved on. We continued as before, riding in a long double rank south and west, slowly leaving behind the friendly hills of the Summer Realm and passing into the arid, drought-blasted barrens of Llyonesse.

The Pendragon, with Myrddin at his right hand, led the way, and I, who had already traversed this perilous path, rode with Rhys just behind them so as to be close to hand if needed. Bors rode behind me, followed by long ranks of warriors stretching back and back, fifty strong. Bedwyr, Cai, and Cador were given command of the rearward forces and took their places far down the line.

The sun, never bright, passed low over the southern hills before sinking once more. The dreary day dwindled away to a long, lingering dusk. Mist gathered thick on the trail and dull clouds lowered above. The voices of the men grew quieter by degrees until we moved in a netherworld between two skies, a world devoid of colour, light, and any sound – save the steady clop, clop, clop of the horses' hooves, hollow and slow on the bare, hard ground.

As the last fleeting glimmer of light faded in the west, we glimpsed a rise of fog on the trail ahead. The closer we came, the more dense it grew, billowing higher and higher until it resembled nothing so much as a massive wall towering over us.

Unwilling to enter the fog blindly, Arthur halted the columns a few hundred paces away so that he might observe for a time. 'Strange that it does not move,' Myrddin said to Arthur. Though he spoke low, his voice carried on the unnaturally still air. 'I advise caution.'

'The day is going and we are losing the light,' the king pointed out. 'We might make camp here and hope the weather clears tomorrow.'

'There is no wood for a fire,' Bedwyr put in.

'Then we will do without,' Arthur said, making up his mind. 'It makes a cold night for us, but that is better than risking our necks on a trail we cannot see.'

At a nod from the king, Rhys raised the hunting horn and signalled the Cymbrogi to dismount. We made camp and spent a chill, damp night on the trail. Dawnlight the next morning revealed that the bank of fog had not shifted or dissipated. Indeed, it now appeared more solid and imposing than before: a vast, gently seething eminence, beyond which neither eye nor ear could penetrate. The wall of mist lay across our path as if marking out the line of battle – as if an enemy had thrown up a defensive rampart and carved upon it the words, 'cross over if you dare.'

We crossed, of course. Having no better choice – there was no riding around it, and waiting was pointless – we formed tight columns and marched forward, breasted the wall, and passed into the mist. I could make out Rhys beside me, but Arthur and Myrddin ahead and those behind were hazy, half-formed figures floating at the perimeter of sight, and beyond that I could see nothing.

As the fog closed like a tight woollen glove around us, I spared a fleeting thought for the phantom legion. Was this how Legio XXII Augustus met its uncanny fate? Had they, like us, marched into the mist, and into the realm of the undead, never to return?

The mist, so close and thick, stole away every sound, even the hollow plod of the horses' hooves and the dull jingle of the tack. The world seemed still and cold and silent, as if offering us a foretaste of death. I ignored the damp chill and gazed staunchly into the quiet, unchanging void, and was surprised when, after a time, I began to hear an odd, rhythmic drumming. Looking around, I could not locate the source of the disturbing sound -until I realized it was the very blood pulsing in my ears with every beat of my heart.

In addition to banishing sight and sound, the fog was heavy and wet. Within moments of entering the mist, I felt the chill weight settle on my shoulders and the cold trickle of water along my spine. Water beaded on my face and moustache, and ran down my head and neck. I gathered my sodden cloak around me, lowered my head, and rode on, thinking, I have been cold before. And I have ridden in mist many times, and will again. It is winter, after all, and mist and fog are to be expected. This is just poor weather, nothing more.

We journeyed an eternity, or so it seemed. With neither light nor shadow to mark the passing day, time dwindled and stretched, and then stood still. Once, my horse stumbled over a rock and I came awake with a cry. Glancing quickly around, I found everything as it was before: dense, cloying fog pressing in on every side. Nothing had changed; nevertheless, I felt vexed at having slept, for, try as I might, I could not remember falling asleep.

'Gwalchavad?' said Rhys, his voice close.

I could make out my companion as a disembodied head peering anxiously back at me as if through a depth of clouded water – the face of a drowned man, bloodless and cold, and pale as a fish. All at once it came into my mind to warn Arthur…

'The river!' I shouted, surprising even myself with the sudden outcry. 'Arthur! Stop! There is a river ahead!'

Arthur's reply was quick and decisive. 'Rhys, the horn,' he said. 'Sound the halt.'

An instant later came the blast of the horn, signalling the column to stop. Arthur passed word back through the ranks to dismount and rest the horses. I slid from the saddle and walked a few paces ahead to where Myrddin and Arthur waited. 'The river is treacherous with quicksand,' I told them. 'I lost my horse to it last time.'

Arthur regarded me with a bemused expression on his face. 'We can see nothing of the trail ahead; how can you be certain we are anywhere near the river?'

His question brought me up short. Before he asked, I had been sure we were ready to topple over the brink. But now, as I observed their expressions of perplexity and concern, the certainty, so solid and secure just a moment before, crumbled away to nothing. I looked to the track before us and saw only the dull blankness of the all-obscuring fog.

I was saved from having to explain when Myrddin, calmly concerned, said, 'Come, it will not hurt to walk ahead a little.' He and Arthur dismounted, and we proceeded up the trail.

We had moved only a few paces, however, when my feet began sinking into soft mud. Arthur, beside me, took another step and his foot splashed into shallow water. He stopped at once, turned towards me, and opened his mouth to speak; but before he could say a word, his feet were sucked down into the quagmire. He threw out a hand, which I seized and pulled towards me. We stumbled backward together onto solid ground.

'Well done, Gwalchavad,' he commended.

The first rider in would have been lost,' Myrddin observed.

'That first rider would have been me,' Arthur declared, shaking cold mud from his feet. 'And others would have followed me in.

'Stay near,' said the king, gripping my shoulder. 'I have need of your discernment.'

That was all he said, but I sensed urgency in his touch. 'What little I have is yours, lord,' I said lightly.

'How do we get across?' wondered Cador, coming up behind us.

'There is a fording place some way up the valley,' I told him.

'Lead on, Gwalchavad,' the king commanded; 'we will follow you.'