At this I began to doubt. What did I hope to prove by making him swear his faith and loyalty before the altar? It was, as he had said, a meaningless exercise and would prove nothing.

I felt hard bone and muscle under my hand and doubt stole over me. Fool! What are you doing? Has the enemy so confused and deceived you that you can no longer tell the difference between friend and foe? Let him go!

As if echoing my thoughts, Peredur said, 'Let me go -1 will not think the worse of you. Trust me; we can still find the others, but we must hurry.'

If I had been alone, I believe I would have released him then and there. The urge to do so was stronger than my conviction to see the thing through. But Bors, when roused, is not easily put off. 'Save your breath,' he told the young warrior flatly. 'It is soon over, and no harm will come to you.'

With that we marched to the chapel door, whereupon I removed the knife from his throat and, shifting my free hand to the back of his head, pushed Peredur down so he could navigate the low entrance. He stooped and bent his back as he entered the narrow opening. But as his foot touched the threshold, he suddenly froze.

'No!' he shouted, and made to squirm away. I renewed my grip on his arm and held him tight. 'It proves nothing. I will not do it.'

Bors, close behind, put out a hand and pushed him further into the narrow opening. The young man arched his back and dug in his heels.

'Get on with it, man,' Bors urged roughly. There is nothing to fear.'

'No!' he cried again, almost frantic this time, his fingers raking at the pillar stones of the entrance. 'No!'

Bors, larger and stronger, pushed him further through the doorway. Twisting and turning, Peredur fought, resisting with all his strength. He shouted to be released, his distress turning quickly to rage. Bors, however, was growing ever more determined and would not be moved. He stooped and, with a mighty heave, shoved the struggling warrior through the low entrance and into the chapel.

Bors followed him through and I pushed quickly in behind them. Peredur had landed on hands and knees on the stone-flagged floor, and Bors stood over him, reaching down a hand to raise him up. I joined Bors and, taking hold of the young man's arm, said, 'Here, now – come stand before the altar.'

As I took his arm, I felt a tremor pass through his body. His head whipped around, mouth open to bite my hand. With but a fleeting glimpse of his face, I released my hold and leapt aside. 'Bors!' I cried. 'Get back!'

In the same instant, Peredur gave out a tremendous guttural growl and rose up, flinging Bors aside as if he were no more than a toddling child. Bors fell on his side, his head striking the stone floor. He made to rise and collapsed. I dove to his aid as Peredur, shaking in every limb, began howling like an animal.

'Bors!' I cried, trying to shake him awake. 'Can you hear me? Get up!'

A ragged snarl of rage filled the chapel. I glanced over my shoulder to where Peredur stood. I no longer recognized him at all: his neck was bent, forcing his head down low onto his chest; his lower jaw jutted out and his mouth gaped, revealing teeth both sharp and oddly curved; his shoulders and arms were thicker, his back more broad, with humps of powerful muscle. But it was his eyes that startled me most – red-rimmed and wild, they bulged out of their sockets as if they would burst from within.

Still howling, he turned and slowly stepped towards me, long hands with fingers like claws, twitching and reaching. Bors was still unconscious, and I could not leave him. I looked for his sword, but could not see it.

'Gereint!' I shouted.

He entered the chapel at a run. Without a quiver of hesitation, Gereint interposed himself between the monstrous Peredur and me, his blade drawn. Taking no heed, the thing lurched nearer, growling and slavering like a wolf for the kill.

Gereint held his ground; the blade in his hand never wavered. Heedless of the sword, the brute lunged and made a raking swipe, which the young warrior deftly deflected. The howling thing received a quick slash on the arm. 'In God's name, stay back!' warned Gereint.

At this the creature threw back its head and shrieked, gnashing its teeth and clawing at the air. Then, still shrieking, it started forth once more. Bors came awake at the sound. He pushed himself up from the floor and struggled to rise – only to slump back once more. 'I am with you, brother,' I said, holding to him so as to protect him.

On a sudden inspiration, Gereint grasped the naked blade and turned it in his hand, presenting the hilt upward in imitation of the Holy Cross – as Arthur had done at the consecration of the Grail Shrine. Taking the blade in both hands, he held the sword hilt before him, thrusting it at arm's length into the brute's face.

The creature roared, and staggered backward. Gereint advanced, holding the sword-cross and calling, 'In Jesu's holy name, be gone!'

The brute loosed a mind-freezing scream and began clawing at itself, as if to tear the ears from its own hideous head. It sank to its knees, wailing, keening, gnashing its teeth. Dauntless Gereint bore down upon it, calling upon Christ to drive the thing away.

The wicked thing shrieked and shrieked again to drown out all sound but that of its own torment. Then, even as we watched, the thing began to change again: its body stretched, growing thinner and taller, until its narrow head almost touched the rooftrees of the chapel – whereupon it could no longer support its height and fell, doubling over itself, to writhe and thrash, beating itself upon the floor.

Gereint, unyielding, his face hard as flint, clutched his improvised cross and stood implacable. Wailing pitifully, the creature continued its hideous transformation, its thin body becoming small and scaly and its terrible voice waning away to a high, hissing scream. It rolled in its writhing coils and then slithered for the chapel door, where, with the speed of a fleeing serpent, it slipped over the threshold and disappeared into the night beyond.

The young warrior, still clutching the sword-cross, hastened to where I knelt with Bors. 'It has gone,' he said, his voice hollow, his face drained.

'Well done, Gereint,' I told him, and noticed the blood dripping from his hands. He had gripped the sword blade so tightly, he had cut his palms and fingers. I reached for the hilt. 'You can let go now, son. The fight is over.'

Gereint released the sword, which I returned to its place at his side, then helped him cut strips from his cloak to bind his hands. I tied the strips in place, and we turned our attention to Bors. Between us, we rolled the big man onto his back, bunched up his cloak, and put it beneath his head to make him as comfortable as possible. Then Gereint and I sat down together; leaning against the stout wall, we rested and talked about what had happened.

'What do you think it was?' Gereint wondered. 'A shape-shifter?'

'A demon maybe,' I replied. 'I have heard Bishop Elfodd tell about such things.'

'Is that why you thought to bring it into the church?'

'Truly, I do not know what I thought,' I confessed. 'I only knew that Peredur was a devout man and it would be no hardship for him to take an oath before the altar.'

'But how did you know it was not Peredur?'

'Something about his manner made me suspicious. I cannot say what it was. But then' -1 shrugged – 'it seemed silly to hold such a small thing against him. I doubted myself and almost let him go.'

'But how did you know?' Gereint asked, then added ruefully, 'I was taken in completely.'

'There is no shame in it,' I assured him. 'As to what warned me, I can but say I did not like his manner. When I spoke of the Grail, he behaved as if it were a thing of no importance.'

'Yes!' agreed Gereint. 'The true Peredur would have wanted to see it.'