"Something ahead!" Thorvald did not slacken the pace set by the brilliant spot of green they trailed. Both of the Terrans feared to fall behind, to lose touch with that guide. Their belief that somehow the traveling disk would bring them to the end of the mist and its attendant illusions had grown firmer with every foot of ground they traversed.

A dark, fixed point, now partly veiled by mist, lay beyond, and it was toward that looming half-shadow that the spinning disk hurtled. Now the mist curled away to display its bulk—larger, blacker and four or five times Thorvald's height. Both men stopped short, for the disk no longer played pathfinder. It still whirled on its axis in the air, faster and faster, until it appeared to be throwing off sparks, but the sparks faded against a monolith of dark rock unlike the native stone they had seen elsewhere. For it was neither red nor warmly brown, but a dull, dead black. It could have been a huge stone slab, trimmed, smoothed, set up on end as a monument or marker, except that only infinite labor could have accomplished such a task, and there was no valid reason for such toil as far as the Terrans could perceive.

"This is it." Thorvald moved closer.

By the disk's action, they deduced that their guide had drawn them to this featureless black steel with the precision of a beam-controlled ship. However, the purpose still eluded them. They had hoped for some exit from the territory of the veil, but now they faced a solid slab of dark stone, neither a conventional exit or entrance, as they proved by circling its base. Beneath their boots was the eternal sand, around them the fog.

"Now what?" Shann asked. They had made their trip about the slab and were back again where the disk whirled with unceasing vigor in a shower of emerald sparks.

Thorvald shook his head, scanning the rock face before them glumly. The eagerness had gone out of his expression, a vast weariness replacing it.

"There must have been some purpose in coming here," he replied, but his tone had lost the assurance of moments earlier.

"Well, if we strike away from here, we'll just get right back in again." Shann waved a hand toward the mist, waiting as if with a hunter's watch upon them. "And we certainly can't go down." He dug a boot toe into the sand to demonstrate the folly of that. "So, what about up?"

He ducked under the spinning disk to lay his hands against the surface of the giant slab. And in so doing he made a discovery, revealed to his touch although hidden from sight. For his fingers, running aimlessly across the cold, slightly uneven surface of the stone, slipped into a hollow, quite a deep hollow.

Excited, half fearing that his sudden guess might be wrong, Shann slid his hand higher in line with that hollow, to discover a second. The first had been level with his chest, the second perhaps eighteen inches or so above. He jumped, to draw his fingers down the rock, with damage to his nails but getting his proof. There was a third niche, deep enough to hold more than just the toe of a boot, and a fourth above that....

"We've a ladder of sorts here," he reported. Without waiting for any answer from Thorvald, Shann began to climb. The holds were so well matched in shape and size that he was sure they could not be natural; they had been bored there for use—the use to which he was now putting them—a ladder to the top of the slab. Though what he might find there was beyond his power to imagine.

The disk did not rise. Shann passed that core of light, climbing above it into the greater gloom. But the holes did not fail him; each was waiting in a direct line with its companion. And to an active man the scramble was not difficult. He reached the summit, glanced around, and made a quick grab for a secure handhold.

Waiting for him was no level platform such as he had confidently expected to find. The surface up which he had just made his way fly-fashion was the outer wall of a well or chimney. He looked down now into a pit where black nothingness began within a yard of the top, for the radiance of the mist did not penetrate far into that descent.

Shann fought an attack of giddiness. It would be very easy to lose control, to tumble over and be swallowed up in what might well be a bottomless chasm. And what was the purpose of this well? Was it a trap to entice a prisoner into an unwary climb and then let gravity drag him over? The whole setup was meaningless. Perhaps meaningless only to him, Shann conceded, with a flash of level thinking. The situation could be quite different as far as the natives were concerned. This structure did have a reason, or it would never have been erected in the first place.

"What's the matter?" Thorvald's voice was rough with impatience.

"This thing's a well." Shann edged about a fraction to call back. "The inside is open and—as far as I can tell—goes clear to the planet's core."

"Ladder on the inside too?"

Shann squirmed. That was, of course, a very obvious supposition. He kept a tight hold with his left hand, and with the other, he did some exploring. Yes, here was a hollow right enough, twin to those on the outside. But to swing over that narrow edge of safety and begin a descent into the black of the well was far harder than any action he had taken since the morning the Throgs had raided the camp. The green mist could hold no terrors greater than those with which his imagination peopled the depths now waiting to engulf him. But Shann swung over, fitted his boot into the first hollow, and started down.

The only encouragement he gained during that nightmare ordeal was that those holes were regularly spaced. But somehow his confidence did not feed on that fact. There always remained the nagging fear that when he searched for the next it would not be there and he would cling to his perch lacking the needful strength in aching arms and legs to reclimb the inside ladder.

He was fast losing that sense of well being which had been his during his travels through the fog; a fatigue tugged at his arms and weighed leaden on his shoulders. Mechanically he prospected for the next hold, and then the next. Above, the oblong of half-light grew smaller and smaller, sometimes half blotted out by the movements of Thorvald's body as the other followed him down that interior way.

How far was down? Shann giggled lightheadedly at the humor of that, or what seemed to be humor at the moment. He was certain that they were now below the level of the sand floor outside the slab. And yet no end had come to the well hollow.

No break of light down here; he might have been sightless. But just as the blind develop an extra perceptive sense of unseen obstacles, so did Shann now find that he was aware of a change in the nature of the space about him. His weary arms and legs held him against the solidity of a wall, yet the impression that there was no longer another wall at his back grew stronger with every niche which swung him downward. And he was as sure as if he could see it, that he was now in a wide-open space, another cavern; perhaps, but this one totally dark.

Deprived of sight, he relied upon his ears. And there was a sound, faint, distorted perhaps by the acoustics of this place, but keeping up a continuous murmur. Water! Not the wash of waves with their persistent beat, but rather the rippling of a running stream. Water must lie below!

And just as his weariness had grown with his leaving behind the fog, so now did both hunger and thirst gnaw at Shann, all the sharper for the delay. The Terran wanted to reach that water, could picture it in his mind, putting away the possibility—the probability—that it might be sea-born and salt, and so unfit to drink.

The upper opening to the cavern of the fog was now so far above him that he had to strain to see it. And that warmth which had been there was gone. A dank chill wrapped him here, dampened the holds to which he clung until he was afraid of slipping. While the murmur of the water grew louder, until its slap-slap sounded within arms' distance. His boot toe skidded from a niche. Shann fought to hold on with numbed fingers. The other foot went. He swung by his hands, kicking vainly to regain a measure of footing.

Then his arms could no longer support him, and he cried out as he fell. Water closed about him with an icy shock which for a moment paralyzed him. He flailed out, fighting the flood to get his head above the surface where he could gasp in precious gulps of air.

There was a current here, a swiftly running one. Shann remembered the one which had carried him into that cavern in which the Warlockians had their strange dwelling. Although there were no clusters of crystals in this tunnel to supply him with light, the Terran began to nourish a faint hope that he was again in that same stream, that those light crystals would appear, and that he might eventually return to the starting point of this meaningless journey.

So he strove only to keep his head above water. Hearing a splashing behind him, he called out: "Thorvald?"

"Lantee?" The answer came back at once; the splashing grew louder as the other swam to catch up.

Shann swallowed a mouthful of the water lapping against his chin. The taste was brackish, but not entirely salt, and though it stung his lips, the liquid relieved a measure of his thirst.

Only no glowing crystals appeared to stud these walls, and Shann's hope that they were on their way to the cavern of the island faded. The current grew swifter, and he had to fight to keep his head above water, his tired body reacting sluggishly to commands.

The murmur of the racing flood drummed louder in his ears, or was that sound the same? He could no longer be sure. Shann only knew that it was close to impossible to snatch the necessary breath as he was rolled over and over in the hurrying flood.

In the end he was ejected into blazing, blinding light, into a suffocation of wild water as the bullet in an ancient Terran rifle might have been fired at no specific target. Gasping, beaten, more than half-drowned, Shann was pummeled by waves, literally driven up on a rocky surface which skinned his body cruelly. He lay there, his arms moving feebly until he contrived to raise himself in time to be wretchedly sick. Somehow he crawled on a few feet farther before he subsided again, blinded by the light, flinching from the heat of the rocks on which he lay, but unable to do more for himself.

His first coherent thought was that his speculation concerning the reality of this experience was at last resolved. This could not possibly be an hallucination; at least this particular sequence of events was not. And he was still hazily considering that when a hand fell on his shoulder, fingers biting into his raw flesh.

Shann snarled, rolled over on his side. Thorvald, water dripping from his rags—or rather steaming from them—his shaggy hair plastered to his skull, sat there.

"You all right?"

Shann sat up in turn, shielding his smarting eyes. He was bruised, battered badly enough, but he could claim no major injuries.

"I think so. Where are we?"

Thorvald's lips stretched across his teeth in what was more a grimace than a smile. "Right off the map, any map I know. Take a look."

They were on a scrap of beach—beach which was more like a reef, for it lacked any covering comparable to sand except for some cupfuls of coarse gravel locked in rock depressions. Rocks, red as the rust of dried blood, rose in fantastic water-sculptured shapes around the small semi-level space they had somehow won.

This space was V-shaped, washed by equal streams on either side of the prong of rock by water which spouted from the face of a sheer cliff not too far away, with force enough to spray several feet beyond its exit point. Shann seeing that and guessing at its significance, drew a deep breath, and heard the ghost of an answering chuckle from his companion.

"Yes, that's where we came out, boy. Like to make a return trip?"

Shann shook his head, and then wished that he had not so rashly made that move, for the world swung in a dizzy whirl. Things had happened too fast. For the moment it was enough that they were out of the underground ways, back under the amber sky, feeling the bite of Warlock's sun.

Steadying his head with both hands, Shann turned slowly, to survey what might lie at their backs. The water, pouring by on either side, suggested that they were again on an island. Warlock, he thought gloomily, seemed to be for Terrans a succession of islands, all hard to escape.

The tangle of rocks did not encourage any exploration. Just gazing at them added to his weariness. They rose, tier by tier, to a ragged crown against the sky. Shann continued to sit staring at them.

"To climb that...." His voice trailed into the silence of complete discouragement.

"You climb—or swim," Thorvald stated. But, Shann noted, the Survey officer was not in a hurry to make either move.

Nowhere in that wilderness of rock was there the least relieving bit of purple foliage. Nor did any clak-claks or leather-headed birds tour the sky over their heads. Shann's thirst might have been partially assuaged, but his hunger remained. And it was that need which forced him at last into action. The barren heights promised nothing in the way of food, but remembering the harvest the wolverines had taken from under the rocks along the river, he got to his feet and lurched out on the reef which had been their salvation, hunting some pool which might hold an edible captive or two.

So it was that Shann made the discovery of a possible path consisting of a ledge running toward the other end of the island, if this were an island where they had taken refuge. The spray of the water drenched that way, feeding small pools in the uneven surface, and strips of yellow weed trailed in slimy ribbons back below the surface of the waves.

He called to Thorvald and gestured to his find. And then, close together, linking hands when the going became hazardous, the men followed the path. Twice they made finds in the pools, finned or clawed grotesque creatures, which they killed and ate, wolfing down the few fragments of odd-tasting flesh. Then, in a small crevice, which could hardly be dignified by the designation of "cave," Thorvald chanced upon a quite exciting discovery—a clutch of four greenish eggs, each as large as his doubled fist.

Their outer covering was more like tough membrane than true shell, and the Terrans worried it open with difficulty. Shann shut his eyes, trying not to think of what he mouthed as he sucked his share dry. At least that semi-liquid stayed put in his middle, though he expected disastrous results from the experiment.

More than a little heartened by this piece of luck, they kept on, though the ledge changed from a reasonably level surface to a series of rising, unequal steps, drawing them away from the water. At long last they came to the end of that path. Shann leaned back against a convenient spur of rock.

"Company!" he alerted Thorvald.

The Survey officer joined him to share an outcrop of rock from which they were provided with an excellent view of the scene below, and it was a scene to hold their full attention.

That soft sweep of sand which had floored the cavern of the fog lay here also, a gray-blue carpet sloping gently out of the sea. For Shann had no doubt that the wide stretch of water before them was the western ocean. Walling the beach on either side, and extending well out into the water so that the farthest piles were awash except for their crowns, were pillars of stone, shaped with the same finish as that slab which had provided them a ladder of escape. And because of the regularity of their spacing, Shann did not believe them works of nature.

Grouped between them now were the players of the drama. One of the Warlockian witches, her gem body patterns glittering in the sunlight, was walking backward out of the sea, her hands held palms together, breast high, in a Terran attitude of prayer. And following her something swam in the water, clearly not another of her own species. But her actions suggested that by some invisible means she was drawing that water dweller after her. Waiting on shore were two others of her kind, viewing her actions with close attention, the attention of scholars for an instructor.

"Wyverns!"

Shann looked inquiringly at his companion. Thorvald added a whisper of explanation. "A legend of Terra—they were supposed to have a snake's tail instead of hind legs, but the heads.... They're Wyverns!"

Wyverns. Shann liked the sound of that word; to his mind it well fitted the Warlockian witches. And the one they were watching in action continued her steady backward retreat, rolling her bemused captive out of the water. What emerged into the blaze of sunlight was one of those fork-tailed sea dwellers such as the Terrans had seen die after the storm. The thing crawled out of the shallows, its eyes focused in a blind stare on the praying hands of the Wyvern.

She halted, well up on the sand, when the body of her victim or prisoner—Shann was certain that the fork-tail was one or the other—was completely out of the water. Then, with lightning speed, she dropped her hands.

Instantly fork-tail came to life. Fanged jaws snapped. Aroused, the beast was the incarnation of evil rage, a rage which had a measure of intelligence to direct it into deadly action. And facing it, seemingly unarmed and defenseless, were the slender, fragile Wyverns.

Yet none of the small group of natives made any attempt to escape. Shann thought them suicidal in their indifference as fork-tail, short legs sending the fine sand flying in a dust cloud, made a rush toward its enemies.

The Wyvern who had led the beast ashore did not move. But one of her companions swung up a hand, as if negligently waving the monster to a stop. Between her first two digits was a disk. Thorvald caught at Shann's arm.

"See that! It's a copy of the one I had; it must be!"

They were too far away to be sure it was a duplicate, but It was coin-shaped and bone-white. And now the Wyvern swung it back and forth in a metronome sweep. Fork-tail skidded to a stop, its head beginning—reluctantly at first, and then, with increasing speed—to echo that left-right sweep. This Wyvern had the sea beast under control, even as her companion had earlier held it.

Chance dictated what happened next. As had her sister charmer, the Wyvern began a backward withdrawal up the length of the beach, drawing the sea thing in her wake. They were very close to the foot of the drop above which the Terrans stood, fascinated, when the sand betrayed the witch. Her foot slipped into a hole and she was thrown backward, her control disk spinning out of her fingers.

At once the monster she had charmed shot forth its head, snapped at that spinning trifle—and swallowed it. Then the fork-tail hunched in a posture Shann had seen the wolverines use when they were about to spring. The weaponless Wyvern was the prey, and both her companions were too far away to interfere.

Why he moved he could not have explained. There was no reason for him to go to the aid of the Warlockian, one of the same breed who had ruled him against his will. But Shann sprang, landing in the sand on his hands and knees.

The sea thing whipped around, undecided between two possible victims. Shann had his knife free, was on his feet, his eyes on the beast's, knowing that he had appointed himself dragon slayer for no good reason.