As the raft revolved slowly it also slipped downstream at a steadily increasing pace, for the current had them in hold. The wolverines pressed close to Shann until the musky scent of their fur, their animal warmth, enveloped him. One growled deep in its throat, perhaps in answer to that wind-borne wail.

"Hound?" Shann asked.

Beside him in the dark Thorvald was working loose one of the poles they had readied to help control the raft's voyaging. The current carried them along, but there was a need for those lengths of sapling to fend them free from rocks and water-buried snags.

"What hound?" the younger man demanded more sharply when there came no immediate answer.

"The Throgs' tracker. But why did they import one?" Thorvald's puzzlement was plain in his tone. He added a moment later, with some of his usual firmness, "We may be in for bad trouble now. Use of a hound means an attempt to take prisoners——"

"Then they do not know that we are here, as Terrans, I mean?"

Thorvald seemed to be sorting out his thoughts when he replied to that. "They could have brought a hound here just on chance that they might miss one of us in the initial mop-up. Or, if they believe we are natives, they could want a specimen for study."

"Wouldn't they just blast down Terrans on sight?"

Shann saw the dark blot which was Thorvald's head shake in negation.

"They might need a live Terran—badly and soon."

"Why?"

"To operate the camp call beam."

Shann's momentary bewilderment vanished. He knew enough of Survey procedure to guess the reason for such a move on the part of the aliens.

"The settler transport?"

"Yes, the ship. She won't planet here without the proper signal. And the Throgs can't give that. If they don't take her, their time's run out before they have even made a start here."

"But how could they know that the transport is nearly due? When we intercept their calls they're pure gibberish to us. Can they read our codes?"

"The supposition is that they can't. Only, concerning Throgs, all we know is supposition. Anyway, they do know the routine for establishing a Terran colony, and we can't alter that procedure except in small nonessentials," Thorvald said grimly. "If that transport doesn't pick up the proper signal to set down here on schedule, her captain will call in the patrol escort ... then exit one Throg base. But if the beetle-heads can trick the ship in and take her, then they'll have a clear five or six more months here to consolidate their own position. After that it would take more than just one patrol cruiser to clear Warlock; it will require a fleet. So the Throgs will have another world to play with, and an important one. This lies on a direct line between the Odin and Kulkulkan systems. A Throg base on such a trade route could eventually cut us right out of this quarter of the galaxy."

"So you think they want to capture us in order to bring the transport in?"

"By our type of reasoning, that would be a logical move—if they know we are here. They haven't too many of those hounds, and they don't risk them on petty jobs. I'd hoped we'd covered our trail well. But we had to risk that attack on the camp.... I needed the map case!" Again Thorvald might have been talking to himself. "Time ... and the right maps—" he brought his fist down on the raft, making the platform tremble—"that's what I have to have now."

Another patch of light-willows stretched along the river-banks, and as they sailed through that ribbon of ghostly radiance they could see each other's faces. Thorvald's was bleak, hard, his eyes on the stream behind them as if he expected at any moment to see a Throg emerge from the surface of the water.

"Suppose that thing—" Shann pointed upstream with his chin—"follows us? What is it anyway?" Hound suggested Terran dog, but he couldn't stretch his imagination to believe in a working co-operation between Throg and any mammal.

"A rather spectacular combination of toad and lizard, with a few other grisly touches, is about as close as you can get to a general description. And that won't be too accurate, because like the Throgs its remote ancestors must have been of the insect family. If the thing follows us, and I think we can be sure that it will, we'll have to take steps. There is always this advantage—those hounds cannot be controlled from a flyer, and the beetle-heads never take kindly to foot slogging. So we won't have to expect any speedy chase. If it slips its masters in rough country, we can try to ambush it." In the dim light Thorvald was frowning. "I flew over the territory ahead on two sweeps, and it is a queer mixture. If we can reach the rough country bordering the sea, we'll have won the first round. I don't believe that the Throgs will be in a hurry to track us in there. They'll try two alternatives to chasing us on foot. One, use their energy beams to rake any suspect valley, and since there are hundreds of valleys all pretty much alike, that will take some time. Or they can attempt to shake us out with a dumdum should they have one here, which I doubt."

Shann tensed. The stories of the effects of the Throg's dumdum weapon were anything but pretty.

"And to get a dumdum," Thorvald continued as if he were discussing a purely theoretical matter and not a threat of something worse than death, "They'll have to bring in one of their major ships. Which they will hesitate to do with a cruiser near at hand. Our own danger spot now is the section we should strike soon after dawn tomorrow if the rate of this current is what I have timed it. There is a band of desert on this side of the mountains. The river gorge deepens there and the land is bare. Let them send a ship over and we could be as visible as if we were sending up flares——"

"How about taking cover now and going on only at night?" suggested Shann.

"Ordinarily, I'd say yes. But with time pressing us now, no. If we keep straight on, we could reach the foothills in about forty hours, maybe less. And we have to stay with the river. To strike across country there without good supplies and on foot is sheer folly."

Two days. With perhaps the Throgs unleashing their hound on land, combing from their flyers. With a desert.... Shann put out his hands to the wolverines. The prospect certainly didn't seem anywhere near as simple as it had the night before when Thorvald had planned this escape. But then the Survey officer had left out quite a few points which were not pertinent. Was he also leaving out other essentials? Shann wanted to ask, but somehow he could not.

After a while he dozed, his head resting on his knees. He awoke, roused out of a vivid dream, a dream so detailed and so deeply impressed in a picture on his mind that he was confused when he blinked at the riverbank visible in the half-light of early dawn.

Instead of that stretch of earth and ragged vegetation now gliding past him as the raft angled along, he should have been fronting a vast skull stark against the sky—a skull whose outlines were oddly inhuman, from whose eyeholes issued and returned flying things while its sharply protruding lower jaw was lapped by water. In color that skull had been a violent clash of blood-red and purple. Shann blinked again at the riverbank, seeing transposed on it still that ghostly haze of bone-bare dome, cavernous eyeholes and nose slit, fanged jaws. That skull was a mountain, or a mountain was a skull—and it was important to him; he must locate it!

He moved stiffly, his legs and arms cramped but not cold. The wolverines stirred on either side of him. Thorvald continued to sleep, curled up beyond, the pole still clasped in his hands. A flat map case was slung by a strap about his neck, its thin envelope between his arm and his body as if for safekeeping. On the smooth flap was the Survey seal, and it was fastened with a finger lock.

Thorvald had lost some of the bright hard surface he had shown at the spaceport where Shann had first sighted him. There were hollows in his cheeks, sending into high relief those bone ridges beneath his eye sockets, giving him a faint resemblance to the skull of Shann's dream. His face was grimed, his field uniform stained and torn. Only his hair was as bright as ever.

Shann smeared the back of his hand across his own face, not doubting that he must present an even more disreputable appearance. He leaned forward cautiously to look into the water, but that surface was not quiet enough to act as a mirror.

Getting to his feet as the raft bobbed under his shift of weight, Shann studied the territory now about them. He could not match Thorvald's inches, just as he must have a third less bulk than the officer, but standing, he could sight something of what now lay beyond the rising banks of the cut. That grass which had been so thick in the meadowlands around the camp had thinned into separate clumps, pale lavender in color. And the scrawniness of stem and blade suggested dehydration and poor soil. The earth showing between those clumps was not of the usual blue, but pallid, too, bleached to gray, while the bushes along the stream's edge were few and smaller. They must have crossed the line into the desert Thorvald had promised.

Shann edged around to face west. There was light enough in the sky to sight tall black pyramids waiting. They had to reach those distant mountains, mountains whose feet on the other side were resting in sea water. He studied them carefully, surveying each peak he could separate from its fellows.

Did the skull lie among them? The conviction that the place he had seen in his dream was real, that it was to be found on Warlock, persisted. Not only was it a definite feature of the landscape somewhere in the wild places of this world, but it was also necessary for him to locate it. Why? Shann puzzled over that, with a growing uneasiness which was not quite fear, not yet, anyway.

Thorvald moved. The raft tilted and the wolverines became growly. Shann sat down, one hand out to the officer's shoulder in warning. Feeling that touch Thorvald shifted, one hand striking out blindly in a blow which Shann was just able to avoid while with the other he pinned the map case yet tighter to him.

"Take it easy!" Shann urged.

The other's eyelids flicked. He looked up, but not as if he saw Shann at all.

"The Cavern of the Veil——" he muttered. "Utgard...." Then his eyes did focus and he sat up, gazing around him with a frown.

"We're in the desert," Shann announced.

Thorvald got up, balancing on feet planted a little apart, looking to the faded expanse of the waste spreading from the river cut. He stared at the mountains before he squatted down to fumble with the lock of the map case.

The wolverines were growing restless, though they still did not try to move about too freely on the raft, greeting Shann with vocal complaint. He and Thorvald could satisfy their hunger with a handful of concentrates from the survival kit. But those dry tablets could not serve the animals. Shann studied the terrain with more knowledge than he had possessed a week earlier. This was not hunting land, but there remained the bounty of the river.

"We'll have to feed Taggi and Togi," he broke the silence abruptly. "If we don't, they'll be into the river and off on their own."

Thorvald glanced up from one of the tough, thin sheets of map skin, again as if he had been drawn back from some distance. His eyes moved from Shann to the unpromising shore.

"How? With what?" he wanted to know. Then the real urgency of the situation must have penetrated his mental isolation. "You have an idea——?"

"There's those fish we found them eating back by the mountain stream," Shann said, recalling an incident of a few days earlier. "Rocks here, too, like those the fish were hiding under. Maybe we can locate some of them here."

He knew that Thorvald would be reluctant to work the raft in shore, to spare time for such hunting. But there would be no arguing with hungry wolverines, and he did not propose to lose the animals for the officer's whim.

However, Thorvald did not protest. They poled the raft out of the main pull of the current, sending it in toward the southern shore in the lee of a clump of light-willows. Shann scrambled ashore, the wolverines after him, sniffling along at his heels while he overturned likely looking rocks to unroof some odd underwater dwellings. The fish with the rudimentary legs were present and not agile enough even in their native element to avoid well-clawed paws which scooped them neatly out of the river shallows. There was also a sleek furred creature with a broad flat head and paddle-equipped forepaws, rather like a miniature seal, which Taggi appropriated before Shann had a chance to examine it closely. In fact, the wolverines wrought havoc along a half-mile section of bank before the Terran could coax them back to the raft.

As they hunted, Shann got a better idea of the land about the river. It was sere, the vegetation dwindling except for some rough spikes of things pushing through the parched ground like flayed fingers, their puffed redness in contrast to the usual amethystine coloring of Warlock's growing things. Under the climbing sun that whole stretch of country was revealed in a stark bareness which at first repelled, and then began to interest him.

He discovered Thorvald standing on the upper bluff, looking out toward the waiting mountains. The officer turned as Shann urged the wolverines to the raft, and when he jumped down the drop to join them, Shann saw he carried a map strip unrolled in his hand.

"The situation is not as good as we hoped," he told the younger man. "Well have to leave the river to cross the heights."

"Why?"

"There're rapids—bending in a falls." The officer squatted down, spreading out the strip and making stabs at it with a nervous finger tip. "Here we have to leave. This is all rough ground. But lying to the south there's a gap which may be a pass. This was made from an aerial survey."

Shann knew enough to realize to what extent such a guide could go wrong. Main features of the landscape would be clear enough from aloft, but there might be unsurmountable difficulties at ground level which were not distinguishable from the air. Yet Thorvald had planned this journey as if he had already explored their escape route and that it was as open and easy as a stroll down Tyr's main transport way. Why was it so necessary that they try to reach the sea? However, since he had no objection to voice except a dislike for indefinite information, Shann did not question the other's calm assumption of command, not yet, anyway.

As they embarked and worked back into the current, Shann studied his companion. Thorvald had freely listed the difficulties lying before them. Yet he did not seem in the least worried about their being able to win through to the sea—or if he was, his outer shell of unconcern remained uncracked. Before their first day together had ended, the younger Terran had learned that to Thorvald he was only another tool, to be used by the Survey officer in some project which the other believed of primary importance. And his resentment of the valuation was under control so far. He valued Thorvald's knowledge, but the other's attitude chilled and rebuffed his need for something more than a half partnership of work.

Why had Thorvald come back to Warlock in the first place? And why had it been necessary for him to risk his life—perhaps more than his life if their theory was correct concerning the Throgs' wish to capture a Terran—to get that set of maps from the plundered camp? When he had first talked of that raid, his promised loot had been supplies to fill their daily needs; there had been no mention of maps. By all signs Thorvald was engaged on some mission. And what would happen if he, Shann, suddenly stopped being the other's obedient underling and demanded a few explanations here and now?

Only Shann knew enough about men to also know that he would not get any information out of Thorvald that the latter was not ready to give, and that such a showdown, coming prematurely, would only end in his own discomfiture. He smiled wryly now, remembering his emotions when he had first seen Ragnar Thorvald months ago. As if the officer ever considered the likes, dislikes—or dreams—of one Shann Lantee. No, reality and dreams seldom approached each other. Dreams....

"On any of those shoreline maps," he asked suddenly, "do they have marked a mountain shaped like a skull?"

Thorvald thrust with his pole. "Skull?" he repeated, a little absently, as he so often did in answer to Shann's questions unless they dealt with some currently important matter.

"A queer sort of skull," Shann said. Just as vividly as when he had first awakened, he could picture that skull mountain with the flying things about its eye sockets. And that, too, was odd; dream impressions usually faded with the passing of waking hours. "It has a protruding lower jaw and the waves wash that ... red-and-purple rock——"

"What?"

He had Thorvald's complete attention now.

"Where did you hear about it?" That demand followed quickly.

"I didn't hear about it. I dreamed of it last night. I stood there right in front of it. There were birds—or things flying like birds—going in and out of the eyeholes——"

"What else?" Thorvald leaned across his pole, his eyes alive, avid, as if he would pull the reply he wanted out of Shann by force.

"That was all I remember—the skull mountain." He did not add his other impression, that he was meant to find that skull, that he must find it.

"Nothing...." Thorvald paused, and then spoke slowly, with a visible reluctance. "Nothing else? No cavern with a green veil—a wide green veil—strung across it?"

Shann shook his head. "Just the skull mountain."

Thorvald looked as if he didn't quite believe that, but Shann's expression must have been convincing, for he laughed shortly.

"Well, there goes one nice neat theory up in smoke!" he commented. "No, your skull doesn't appear on any of our maps, and so probably my cavern does not exist either. They may both be smoke screens——"

"What——?" But Shann never finished that query.

A wind was rising in the desert to blow across the slit which held the river, carrying with it a fine shifting of sand which coasted down into the water as a gray haze, coating men, animals, and raft, and sighing as snow sighs when it falls.

Only that did not drown out another cry, a thin cry, diluted by the miles of land stretching behind them, but yet carrying that long ululating howl they had heard in the Throg camp. Thorvald grinned mirthlessly.

"The hound's on trail."

He bent to the pole, using it to aid the pace of the current. Shann, chilled in spite of the sun's heat, followed his example, wondering if time had ceased to fight on their side.