Shann took up the piece of soft chalklike stone he had found and drew another short white mark on the rust-red of a boulder well above tide level. That made three such marks, three days since Thorvald had marooned him. And he was no nearer the shore now than he had been on that first morning! He sat where he was by the boulder, aware that he should be up, trying to climb to the less accessible nests of the sea birds. The prisoners, man and wolverines, had cleaned out all those they had discovered on beach and cliffs. But at the thought of more eggs, Shann's stomach knotted in pain and he began to retch.

There had been no sign of Thorvald since Shann had watched him steer between the two westward islands. And the younger Terran's faint hope that the officer would return had died. On the shore a few feet away lay his own pitiful attempt to solve the problem of escape.

The force ax had vanished with Thorvald, along with all the rest of the meager supplies which had been the officer's original contribution to their joint equipment. Shann had used his knife on brush and small trees, trying to put together some kind of a raft. But he had not been able to discover here any of those vines necessary for binding, and his best efforts had all come to grief when he tried them in a lagoon launching. So far he had achieved no form of raft which would keep him afloat longer than five minutes, let alone support three of them as far as the next island.

Shann pulled listlessly at the framework of his latest try, fully disheartened. He tried not to think of the unescapable fact that the water in the rain tank had sunk to only an inch or so of muddy scum. Last night he had dug in the heart of the interior valley where the rankness of the vegetation was a promise of moisture, to uncover damp clay and then a brackish ooze. Far too little to satisfy both him and the animals.

There were surely fish somewhere in the lagoon. Shann wondered if the raw flesh of sea dwellers could supply the water they needed. But lacking net, line, or hooks, how did one fish? Yesterday, using his stunner, he had brought down a bird, to discover the carcass so rank even the wolverines, never dainty eaters, refused to gnaw it.

The animals prowled the two beaches, and Shann guessed they hunted shell dwellers, for at times they dug energetically in the gravel. Togi was busied in this way now, the sand flowing from under her pumping legs, her claws raking in good earnest.

And it was Togi's excavation which brought Shann a first ray of hope. Her excitement was so marked that he believed she was in quest of some worthwhile game and he moved across to inspect the pit. A patch of brown, which had been skimmed bare by one raking paw, made him shout.

Taggi shambled downslope, going to work beside his mate with an eagerness as open as hers. Shann hovered at the edge of the pit they were rapidly enlarging. The brown patch was larger, disclosing itself as a hump doming up from the gravel. The Terran did not need to run his hands over that rough surface to recognize the nature of the find. This was another shell such as had come floating in after the storm to form the raw material of their canoe.

However, as fast as the wolverines dug, they did not appear to make correspondingly swift headway in uncovering their find as might reasonably be expected. In fact, a witness could guess that the shell was sinking at a pace only a fraction slower than the burrowers were using to free it. Intrigued by that, Shann went back to the waterline, secured one of the lengths he had been trying to weave into his failures, and returned to use it as a makeshift shovel.

Now, with three of them at the digging, the brown hump was uncovered, and Shann pried down around its edge, trying to lever it up and over. To his amazement, his tool was caught and held, nearly jerked from his hands. To his retaliating tug the obstruction below-ground gave way, and the Terran sprawled back, the length of wood coming clear, to show the other end smashed and splintered as if it had been caught between mashing gears.

For the first time he understood that they were dealing not with an empty shell casing buried by drift under this small beach, but with a shell still inhabited by the Warlockian to whom it was a natural covering, and that that inhabitant would fight to continue ownership. A moment's examination of that splintered wood also suggested that the shell's present wearer appeared well able to defend itself.

Shann attempted to call off the wolverines, but they were out of control now, digging frantically to get at this new prey. And he knew that if he pulled them away by force, they were apt to turn those punishing claws and snapping jaws on him.

It was for their protection that he returned to digging, though he no longer tried to pry up the shell. Taggi leaped to the top of that dome, sweeping paws downward to clear its surface, while Togi prowled around its circumference, pausing now and then to send dirt and gravel spattering, but treading warily as might one alert for a sudden attack.

They had the creature almost clear now, though the shell still rested firmly on the ground, and they had no notion of what it might protect. It was smaller, perhaps two thirds the size of the one which Thorvald had fashioned into a seagoing craft. But it could provide them with transportation to the mainland if Shann was able to repeat the feat of turning it into an outrigger canoe.

Taggi joined his mate on the ground and both wolverines padded about the dome, obviously baffled. Now and then they assaulted the shell with a testing paw. Claws raked and did not leave any marks but shallow scratches. They could continue that forever, as far as Shann could see, without solving the problem in the least.

He sat back on his heels and studied the scene in detail. The excavation holding the shelled creature was some three yards above the high-water mark, with a few more feet separating that from the point where lazy waves now washed the finer sand. Shann watched the slow inward slip of those waves with growing interest. Where their combined efforts had failed to win this odd battle, perhaps the sea itself could now be pressed into service.

Shann began his own excavation, a trough to lead from the waterline to the pit occupied by the obstinate shell. Of course the thing living in or under that covering might be only too familiar with salt water. But it had placed its burrow, or hiding place, above the reach of the waves and so might be disconcerted by the sudden appearance of water in its bed. However, the scheme was worth trying, and he went to work doggedly, wishing he could make the wolverines understand so they would help him.

They still prowled about their captive, scrapping at the sand about the shell casing. At least their efforts would keep the half-prisoner occupied and prevent its escape. Shann put another piece of his raft to work as a shovel, throwing up a shower of sand and gravel while sweat dampened his tattered blouse and was salt and sticky on his arms and face.

He finished his trench, one which ran at an angle he hoped would feed water into the pit rapidly once he knocked away the last barrier against the waves. And, splashing out into the green water, he did just that.

His calculations proved correct. Waves lapped, then flowed in a rapidly thickening stream, puddling out about the shell as the wolverines drew back, snarling. Shann lashed his knife fast to a stout length of sapling, so equipping himself with a spear. He stood with it ready in his hand, not knowing just what to expect. And when the answer to his water attack came, the move was so sudden that in spite of his preparation he was caught gaping.

For the shell fairly erupted out of the mess of sand and water. A complete fringe of jointed, clawed brown limbs churned in a forward-and-upward dash. But the water worked to frustrate that charge. For one of the pit walls crumbled, over-balancing the creature so that the fore end of the shell lifted from the ground, the legs clawing wildly at the air.

Shann thrust with the spear, feeling the knife point go home so deeply that he could not pull his improvised weapon free. A limb snapped claws only inches away from his leg as he pushed down on the haft with all his strength. That attack along with the initial upset of balance did the job. The shell flopped over, its rounded hump now embedded in the watery sand of the pit while the frantic struggles of the creature to right itself only buried it the deeper.

The Terran stared down upon a segmented under belly where legs were paired in riblike formation. Shann could locate no head, no good target. But he drew his stunner and beamed at either end of the oval, and then, for good measure, in the middle, hoping in one of those three general blasts to contact the thing's central nervous system. He was not to know which of those shots did the trick, but the frantic wiggling of the legs slowed and finally ended, as a clockwork toy might run down for want of winding—and at last projected, at crooked angles, completely still. The shell creature might not be dead, but it was tamed for now.

Taggi had only been waiting for a good chance to do battle. He grabbed one of those legs, worried it, and then leaped to tear at the under body. Unlike the outer shell, this portion of the creature had no proper armor and the wolverine plunged joyfully into the business of the kill, his mate following suit.

The process of butchery was a bloody, even beastly job, and Shann was shaken before it was complete. But he kept at his labors, determined to have that shell, his one chance of escape from the Island. The wolverines feasted on the greenish-white flesh, but he could not bring himself to sample it, climbing to the heights in search of eggs, and making a happy find of a niche filled with the edible moss-fungi.

By late afternoon he had the shell scooped fairly clean and the wolverines had carried away for burial such portions as they had not been able to consume at their first eating. Meanwhile, the leather-headed birds had grown bold enough to snatch up the fragments he tossed out on the water, struggling for that bounty against feeders arising from the depths of the lagoon.

At the coming of dusk Shann hauled the bloodstained, grisly trophy well up the beach and wedged it among the rocks, determined not to lose his treasure. Then he stripped and washed, first his clothing and then himself, rubbing his hands and arms with sand until his skin was tender. He was still exultant at his luck. The drift would supply him with materials for an outrigger. One more day's work—or maybe two—and he could leave. He wrung out his blouse and gazed toward the distant line of the shore. Once he had his new canoe ready he would try to make the trip back in the early morning while the mists were still on the sea. That should give him cover against any Throg flight.

That night Shann slept in the deep fog of bodily exhaustion. There were no dreams, nothing but an unconsciousness which even a Throg attack could not have pierced. He roused in the morning with an odd feeling of guilt. The water hole he had scooped in the valley yielded him some swallows tasting of earth, but he had almost forgotten the flavor of a purer liquid. Munching on a fistful of moss, he hurried down to the shore, half fearing to find the shell gone, his luck out once again.

Not only was the shell where he had wedged it, but he had done better than he knew when he had left it exposed in the night. Small things scuttled away from it into hiding, and several birds arose—scavengers had been busy lightening his unwelcome task for that morning. And seeing how the clean-up process had gone, Shann had a second inspiration.

Pushing the thing down the beach, he sank it in the shallows with several rocks to anchor it. Within a few seconds the shell was invaded by a whole school of spiny-tailed fish, that ate greedily. Leaving his find to their cleansing, Shann went back to prospect the pile of raft material, choosing pieces which could serve for an outrigger frame. He was handicapped as he had been all along by the absence of the vines one could use for lashings. And he had reached the point of considering a drastic sacrifice of his clothing to get the necessary strips when he saw Taggi dragging behind him one of the jointed legs the wolverines had put in storage the day before.

Now and again Taggi laid his prize on the shingle, holding it firmly pinned with his forepaws as he tried to worry loose a section of flesh. But apparently that feat was beyond even his notable teeth, and at length he left it lying there in disgust while he returned to a cache for more palatable fare. Shann went to examine more closely the triple-jointed limb.

The casing was not as hard as horn or shell, he discovered upon testing; it more resembled tough skin laid over bone. With a knife he tried to loosen the skin—a tedious job requiring a great deal of patience, since the tissue tore if pulled away too fast. But with care he acquired a few thongs perhaps a foot long. Using two of these, he made a trial binding of one stick to another, and experimented farther, soaking the whole construction in sea water and then exposing it to the direct rays of the sun.

When he examined his test piece an hour later, the skin thongs had set into place with such success that the one piece of wood might have been firmly glued to the other. Shann shuffled his feet in a little dance of triumph as he went on to the lagoon to inspect the water-logged shell. The scavengers had done well. One scraping, two at the most, would have the whole thing clean and ready to use.

But that night Shann dreamed. No climbing of a skull-shaped mountain this time. Instead, he was again on the beach, laboring under an overwhelming compulsion, building something for an alien purpose he could not understand. And he worked as hopelessly as a beaten slave, knowing that what he made was to his own undoing. Yet he could not halt the making, because just beyond the limit of his vision there stood a dominant will which held him in bondage.

And he awoke on the beach in the very early dawn, not knowing how he had come there. His body was bathed in sweat, as it had been during his day's labors under the sun, and his muscles ached with fatigue.

But when he saw what lay at his feet he cringed. The framework of the outrigger, close to completion the night before, was dismantled—smashed. All those strips of hide he had so laboriously culled were cut—into inch-long bits which could be of no service.

Shann whirled, ran to the shell he had the night before pulled from the water and stowed in safety. Its rounded dome was dulled where it had been battered, but there was no break in the surface. He ran his hands anxiously over the curve to make sure. Then, very slowly, he came back to the mess of broken wood and snipped hide. And he was sure, only too sure, of one thing. He, himself, had wrought that destruction. In his dream he had built to satisfy the whim of an enemy; in reality he had destroyed; and that was also, he believed, to satisfy an enemy.

The dream was a part of it. But who or what could set a man dreaming and so take over his body, make him in fact betray himself? But then, what had made Thorvald maroon him here? For the first time, Shann guessed a new, if wild, explanation for the officer's desertion. Dreams—and the disk which had worked so strangely on Thorvald. Suppose everything the other had surmised was the truth! Then that disk had been found on this very island, and here somewhere must lie a clue to the riddle.

Shann licked his lips. Suppose that Thorvald had been sent away under just such a strong compulsion as the one which had ruled Shann last night? Why was he left behind if the other had been moved away to protect some secret? Was it that Shann himself was wanted here, wanted so much that when he at last found a means of escape he was set to destroy it? That act might have been forced upon him for two reasons: to keep him here, and to impress upon him how powerless he was.

Powerless! A flicker of stubborn will stirred to respond to that implied challenge. All right, the mysterious they had made him do this. But they had underrated him by letting him learn, almost contemptuously, of their presence by that revelation. So warned, he was in a manner armed; he could prepare to fight back.

He squatted by the wreckage as he thought that through, turning over broken pieces. And, Shann realized, he must present at the moment a satisfactory picture of despondency to any spy. A spy, that was it! Someone or something must have him under observation, or his activities of the day before would not have been so summarily countered. And if there was a spy, then there was his answer to the riddle. To trap the trapper. Such action might be a project beyond his resources, but it was his own counterattack.

So now he had to play a role. Not only must he search the island for the trace of his spy, but he must do it in such a fashion that his purpose would not be plain to the enemy he suspected. The wolverines could help. Shann arose, allowed his shoulders to droop, slouching to the slope with all the air of a beaten man which he could assume, whistling for Taggi and Togi.

When they came, his exploration began. Ostensibly he was hunting for lengths of drift or suitable growing saplings to take the place of those he had destroyed under orders. But he kept a careful watch on the animal pair, hoping by their reactions to pick up a clue to any hidden watcher.

The larger of the two beaches marked the point where the Terrans had first landed and where the shell thing had been killed. The smaller was more of a narrow tongue thrust out into the lagoon, much of it choked with sizable boulders. On earlier visits there Taggi and Togi had poked into the hollows among these with their usual curiosity. But now both animals remained upslope, showing no inclination to descend to the water line.

Shann caught hold of Taggi's scruff, pulling him along. The wolverine twisted and whined, but he did not fight for freedom as he would have upon scenting Throg. Not that the Terran had ever believed one of those aliens was responsible for the happenings on the island.

Taggi came down under Shann's urging, but he was plainly ill at ease. And at last he snarled a warning when the man would have drawn him closer to two rocks which met overhead in a crude semblance of an arch. There was a stick of drift protruding from that hollow affording Shann a legitimate excuse to venture closer. He dropped his hold on the wolverines, stooped to gather in the length of wood, and at the same time glanced into the pocket.

Water lay just beyond, making this a doorway to the lagoon. The sun had not yet penetrated into the shadow, if it ever did. Shann reached for the wood, at the same time drawing his finger across the flat rock which would furnish a steppingstone for anything using that door as an entrance to the island.

Wet! Which might mean his visitor had recently arrived, or else merely that a splotch of spray had landed there not too long before. But in his mind Shann was convinced that he had found the spy's entrance. Could he turn it into a trap? He added a piece of drift to his bundle and picked up two more before he returned to the cliff ahead.

A trap.... He revolved in his mind all the traps he knew which could be used here. He already had decided upon the bait—his own work. And if his plans went through—and hope does not die easily—then this time he would not waste his labor either.

So he went back to the same job he had done the day before, making do with skin strips he had considered second-best before, smoothing, cutting. Only the trap occupied his mind, and close to sunset he knew just what he was going to do and how.

Though the Terran did not know the nature of the unseen opponent, he thought he could guess two weaknesses which might deliver the other into his hands. First, the enemy was entirely confident of success in this venture. No being who was able to control Shann as completely and ably as had been done the night before would credit any prey with the power to strike back in force.

Second, such a confident enemy would be unable to resist watching the manipulation of a captive. The Terran was certain that his opponent would be on the scene somewhere when he was led, dreaming, to destroy his work once more.

He might be wrong on both of those counts, but inwardly he didn't believe so. However, he had to wait until the dark to set up his own answer, one so simple he was certain the enemy would not suspect it at all.