'God's truth,' he said, shaking his head, 'it was the singing that woke me. I heard nothing of the bell.'

I stared at him, trying to define his face in the windy darkness. 'Singing?'

Strange to say, but even as I spoke the word, I heard the sound of voices lifted in slow, sonorous chant. Perhaps I had been too taken with the bell to have noticed, but I had not heard the sound before that instant. Nevertheless, Peredur maintained that the chanting had wakened him, and now that he had said it, I heard it, too.

As we stood in the wind-tossed night, discussing this, the moon broke free of the low-flying clouds and cast a thin, watery light over the barren hillscape. The bell tolled and the chanting grew louder, and I turned in the direction of the sound, but saw nothing and so directed my gaze elsewhere.

'There they are,' breathed Peredur, putting his head close to mine. 'Eight of them, I make it.'

'Where?' I searched the moon-shot darkness for a glimpse of what he saw, but found nothing.

There!' answered Peredur; placing his hand on my shoulder, he turned me in the direction he was looking – the same direction I had searched. Now I saw the flickering gleam of eight separate lights aglow on the hilltop. On my honour, I swear the lights had not been there a mere moment before. Yet there they were, bobbing gently along the crest of the hill: torches, held aloft by unseen hands, wafting gently nearer to the sound of chanting and the slow ringing of a bell.

'A poor night, I think, for travelling hereabouts,' I remarked.

'Who can they be?' wondered Peredur, and then suggested we take up our weapons and see.

'No,' I counselled, 'their course will bring them near enough. We will await them here.'

We stood our ground and shortly perceived the phantom glimmer of faces beneath the guttering torches. On they came, passing out of sight briefly as they descended one of the intervening valleys – only to reappear much closer than before. Now they were near enough for us to see that there were nine of them: eight torchbearers led by one who carried the bell -monks, as I had supposed, dressed in priestly robes that billowed in the wind. They were chanting in Latin and ringing their bell so intently that they did not appear to heed us at all; had I been in their place, I doubt if I should have expected to encounter fellow wanderers on such a night.

On they came, their voices low, their steps shuffling slowly, their shapes shifting in the wind-whipped torchlight as their robes blew this way and that. Dust churned up by the gusting wind cast a filthy pall over all, so that they seemed to float along on dirty clouds. When I judged they had come near enough, I stepped forth out of the darkness, my hands upraised to show I carried no weapons.

'Peace to you, good brothers,' I said, speaking boldly to be heard over the whine of the wind.

It was not my intent to frighten them, but an unexpected stranger looming out of the darkness of a storm-blown night might be assumed to set the heart racing. Curiously, the column simply halted, ceasing its chanting at the same instant, so that it seemed the monks had anticipated my sudden appearance.

'I give you good greeting,' I called, stepping nearer. They turned towards me and it was then I saw that their faces were swathed in strips of cloth dressings like those that bind the wounded.

None of them spoke a word. The hiss and flutter of the torches, and the sighing moan of the wind, were the only sounds to be heard in all the world. We all stood looking at one another in silence – Peredur and I on our side, the nine shrouded monks on theirs.

'What do you here on such a foul night?' I asked at last.

The foremost monk carrying the bell deigned to reply. 'We go to worship our lord,' he intoned. 'The time of our release approaches.'

'We have ridden far this day, but we have seen neither church nor chapel hereabouts,' I told him. 'Where is your abbey?'

'Our temple lies beneath the hollow hills,' he said in a voice cracking like the dull, distant thunder.

'We are Christian men, too,' I said, 'and camped nearby. You are welcome to share our fire.'

'Christ!' spat the monk, his anger sharp and quick. 'We know him not.'

Mystified by his denial, I asked, 'Then who do you worship?'

'Mithras!' he proclaimed triumphantly, and the remaining monks murmured the name in approval.

If this arrow was loosed to wound me, I confess it fell a good way short of the mark. For the monk's revelation so surprised me, I merely gaped at him. 'Mithras!' I cried in amazement. 'That old bull-killer departed Britain with the Romans,' I replied – which was what men like Bishop Tudno, Iltyd, and Elfodd taught, holy men and learned, every one.

'Mithras lives!' declared the man with the bell.

So saying, he lifted his hand to his shrouded face and drew aside the wrappings as if they had been a veil.

I beheld a visage ravaged by disease; the wretch's cheeks and nose had been eaten away, his chin was raw, his lips were cankered black, and on his forehead pale bone glinted beneath scab-crusted skin. There was not a thumb's-breadth of healthy flesh on him anywhere, for that which was not rotted away was as dry and cracked as the drought-blighted earth beneath our feet.

Peredur gasped. 'Lepers!'

Ignoring the young man's bad manners, I swallowed my dread and forced what I meant to be a smile of welcome. 'I have extended the hospitality of our hearth, such as it is,' I told them. 'I do not withdraw it now.'

'Fool!' said the leper, his voice a croaking whisper. 'You stand on ground sacred to Mithras.'

The wind tore aside his cloak and in the flickery light I saw the dull glint of an ancient lorica on his chest; a bronze-handled spatha hung from his hip, and a brooch at his shoulder was engraved with the image of a she-wolf and the words 'Legio XXII Augustus.'

'Hail, Mithras!' the leper hissed. 'Bow down!'

These words so alarmed me, I sained myself with the sign of the cross – something the good brothers do in times of trial when seeking comfort of the Heavenly Presence – an instinctive impulse, nothing more, yet the result was staggering.

Instantly, the sky was rent by dry lightning. A searing white flash set the heavens ablaze. Thunder rolled. I threw a hand over my eyes. When I dared look around once more, Peredur and I stood on the hilltop, the wind whipping at our cloaks, curling them about our trembling legs. We were alone. The nine lepers had vanished, leaving nothing behind but the burning stink of brimstone.

Thunder cracked over our heads as if the sky itself would fall in shattered chunks upon the ground. I felt Peredur crowding close beside me. 'Devilry walks among us,' I said, steadying my voice. 'Come, we will hold vigil until morning.'

Returning to our pitiful fire, we heaped up the small supply of brush we had put by and renewed the flame, then sat huddled close to the fire and waited out the long, storm-worried night. Tallaght slept on undisturbed.

When murky daylight finally broke over the barrens, I rose and retraced my steps to the hilltop to look for signs of what had passed in the night, but the wind had done its work too well, and there were no tracks to be seen. I did, however, see the faint smudge of smoke rising from a fire some distance away to the south. Upon rousing Tallaght, we saddled the horses and began making our way to our destination as quickly as possible.

It took longer than I imagined to reach the place, and we arrived to find the camp deserted; only the smouldering ash of a fire remained. Once again Peredur proved his skill. Forbidding us to dismount, he stalked around the camp, eyes down, squatting low now and then, searching this way and that for marks that only he could see.