It chanced, long years ago, that a certain horse-dealer lived in the South of Scotland, near the Border, not very far from Longtown. He was known as Canonbie Dick; and as he went up and down the country, he almost always had a long string of horses behind him, which he bought at one fair and sold at another, generally managing to turn a good big penny by the transaction.

He was a very fearless man, not easily daunted; and the people who knew him used to say that if Canonbie Dick dare not attempt a thing, no one else need be asked to do it.

One evening, as he was returning from a fair at some distance from his home with a pair of horses which he had not succeeded in selling, he was riding over Bowden Moor, which lies to the west of the Eildon Hills. These hills are, as all men know, the scene of some of the most famous of Thomas the Rhymer's prophecies; and also, so men say, they are the sleeping-place of King Arthur and his Knights, who rest under the three high peaks, waiting for the mystic call that shall awake them.

But little recked the horse-dealer of Arthur and his Knights, nor yet of Thomas the Rhymer. He was riding along at a snail's pace, thinking over the bargains which he had made at the fair that day, and wondering when he was likely to dispose of his two remaining horses.

All at once he was startled by the approach of a venerable man, with white hair and an old-world dress, who seemed almost to start out of the ground, so suddenly did he make his appearance.

When they met, the stranger stopped, and, to Canonbie Dick's great amazement, asked him for how much he would be willing to part with his horses.

The wily horse-dealer thought that he saw a chance of driving a good bargain, for the stranger looked a man of some consequence; so he named a good round sum.

The old man tried to bargain with him; but when he found that he had not much chance of succeeding—for no one ever did succeed in inducing Canonbie Dick to sell a horse for a less sum than he named for it at first—he agreed to buy the animals, and, pulling a bag of gold from the pocket of his queerly cut breeches, he began to count out the price.

As he did so, Canonbie Dick got another shock of surprise, for the gold that the stranger gave him was not the gold that was in use at the time, but was fashioned into Unicorns, and Bonnet-pieces, and other ancient coins, which would be of no use to the horse-dealer in his everyday transactions. But it was good, pure gold; and he took it gladly, for he knew that he was selling his horses at about half as much again as they were worth. "So," thought he to himself, "surely I cannot be the loser in the long run."

Then the two parted, but not before the old man had commissioned Dick to get him other good horses at the same price, the only stipulation he made being that Dick should always bring them to the same spot, after dark, and that he should always come alone.

And, as time went on, the horse-dealer found that he had indeed met a good customer.

For, whenever he came across a suitable horse, he had only to lead it over Bowden Moor after dark, and he was sure to meet the mysterious, white-headed stranger, who always paid him for the animal in old-fashioned golden pieces.

And he might have been selling horses to him yet, for aught I know, had it not been for his one failing.

Canonbie Dick was apt to get very thirsty, and his ordinary customers, knowing this, took care always to provide him with something to drink. The old man never did so; he paid down his money and led away his horses, and there was an end of the matter.

But one night, Dick, being even more thirsty than usual, and feeling sure that his mysterious friend must live somewhere in the neighbourhood, seeing that he was always wandering about the hillside when everyone else was asleep, hinted that he would be very glad to go home with him and have a little refreshment.

"He would need to be a brave man who asks to go home with me," returned the stranger; "but, if thou wilt, thou canst follow me. Only, remember this—if thy courage fail thee at that which thou wilt behold, thou wilt rue it all thy life."

Canonbie Dick laughed long and loud. "My courage hath never failed me yet," he cried. "Beshrew me if I will let it fail now. So lead on, old man, and I will follow."

Without a word the stranger turned and began to ascend a narrow path which led to a curious hillock, which from its shape, was called by the country-folk the "Lucken Hare."

It was supposed to be a great haunt of Witches; and, as a rule, nobody passed that way after dark, if they could possibly help it.

Canonbie Dick was not afraid of Witches, however, so he followed his guide with a bold step up the hillside; but it must be confessed that he felt a little startled when he saw him turn down what seemed to be an entrance to a cavern, especially as he never remembered having seen any opening in the hillside there before.

He paused for a moment, looking round him in perplexity, wondering where he was being taken; and his conductor glanced at him scornfully.

"You can go back if you will," he said. "I warned thee thou wert going on a journey that would try thy courage to the uttermost." There was a jeering note in his voice that touched Dick's pride.

"Who said that I was afraid?" he retorted. "I was just taking note of where this passage stands on the hillside, so as to know it another time."

The stranger shrugged his shoulders. "Time enough to look for it when thou wouldst visit it again," he said. And then he pursued his way, with Dick following closely at his heels.

After the first yard or two they were enveloped in thick darkness, and the horse-dealer would have been sore put to it to keep near his guide had not the latter held out his hand for him to grasp. But after a little space a faint glimmering of light began to appear, which grew clearer and clearer, until at last they found themselves in an enormous cavern lit by flaming torches, which were stuck here and there in sconces in the rocky walls, and which, although they served to give light enough to see by, yet threw such ghostly shadows on the floor that they only seemed to intensify the gloom that hung over the vast apartment.

And the curious thing about this mysterious cave was that, along one side of it, ran a long row of horse stalls, just like what one would find in a stable, and in each stall stood a coal-black charger, saddled and bridled, as if ready for the fray; and on the straw, by every horse's side, lay the gallant figure of a knight, clad from head to foot in coal-black armour, with a drawn sword in his mailed hand.

But not a horse moved, not a chain rattled. Knights and steeds alike were silent and motionless, looking exactly as if some strange enchantment had been thrown over them, and they had been suddenly turned into black marble.

There was something so awesome in the still, cold figures and in the unearthly silence that brooded over everything that Canonbie Dick, reckless and daring though he was, felt his courage waning and his knees beginning to shake under him.

In spite of these feelings, however, he followed the old man up the hall to the far end of it, where there was a table of ancient workmanship, on which was placed a glittering sword and a curiously wrought hunting-horn.

When they reached this table the stranger turned to him, and said, with great dignity, "Thou hast heard, good man, of Thomas of Ercildoune—Thomas the Rhymer, as men call him—he who went to dwell for a time with the Queen of Fairy-land, and from her received the Gifts of Truth and Prophecy?"

Canonbie Dick nodded; for as the wonderful Soothsayer's name fell on his ears, his heart sank within him and his tongue seemed to cleave to the roof of his mouth. If he had been brought there to parley with Thomas the Rhymer, then had he laid himself open to all the eldrich Powers of Darkness.

"I that speak to thee am he," went on the white-haired stranger. "And I have permitted thee thus to have thy desire and follow me hither in order that I may try of what stuff thou art made. Before thee lies a Horn and a Sword. He that will sound the one, or draw the other, shall, if his courage fail not, be King over the whole of Britain. I, Thomas the Rhymer, have spoken it, and, as thou knowest, my tongue cannot lie. But list ye, the outcome of it all depends on thy bravery; and it will be a light task, or a heavy, according as thou layest hand on Sword or Horn first."

Now Dick was more versed in giving blows than in making music, and his first impulse was to seize the Sword, then, come what might, he had something in his hand to defend himself with. But just as he was about to lift it the thought struck him that, if the place were full of spirits, as he felt sure that it must be, this action of him might be taken to mean defiance, and might cause them to band themselves together against him.