This was not the first time Dalgard had faced the raging fury of a snake-devil thirsting for a kill. The slaying he had done in the arena was an exception to the rule, not the usual hunter's luck. And now that he saw the creature crouched at the far end of the hall he was ready. Sssuri, also, followed their familiar pattern, separating from his companion and slipping along the wall toward the monster, ready to attract its attention at the proper moment.

Only one doubt remained in Dalgard's mind. This devil had not acted in the normal brainless fashion of its kin. What if it was able to assess the very simple maneuvers, which always before had completely baffled its species, and attacked not the moving merman but the waiting archer?

It was backed against another door, a closed one, as if it had fled for refuge to some aid it had expected and did not find. But as Sssuri moved, its long neck straightened until it was almost at right angles with its narrow shoulders, and from its snake's jaws proceeded a horrific hissing which arose to a scream as its leg muscles tensed for a spring.

At just the right moment Sssuri's arm went back, his spear sang through the air. And the snake-devil, with an incredible twist of its neck, caught the haft of the weapon between its teeth, crunching the iron-hard substance into powder. But with that move it exposed its throat, and the arrow from Dalgard's bow was buried head-deep in the soft inner flesh.

The snake-devil spat out the spear and tried to raise its head. But the muscles were already weakening. It fought the poison long enough to take a single step forward, its small red eyes alight with brainless hate. Then it crashed and lay twisting. Dalgard lowered his bow. There was no need for a second shot.

Sssuri regarded the remains of his spear unhappily. Not only was it the product of long hours of work, but no merman ever felt fully equipped to face the world without such a weapon to hand. He salvaged the barbed head and broke it free of the shred of haft the snake-devil had left. Knotting it at his belt he turned to Dalgard.

"Shall we see what lies beyond?"

Dalgard crossed the hall to test the door. It did not yield to an inward push, but rolled far enough into the wall to allow them through.

On the other side was a room which amazed the scout. The colonists had their laboratory, their workshops, in which they experimented and tried to preserve the remnants of knowledge their forefathers had brought across space, as well as to discover new. But the extent of this storehouse with its bewildering mass of odd machines, tanks, bales, and stocked shelves and tables, was too much to be taken in without a careful and minute examination.

"We are not the first to walk here." Sssuri had given little attention to what was stacked about him. Instead he bent over the disturbed dust in one aisle. Dalgard noted as he went to join the merman that there were gaps on those tables which ran the full length of the room, lines left in the grimy deposit of years which told of things recently moved. And then he saw what had interested Sssuri: tracks, some resembling those which his own bare feet might leave, except that there were only three toes!

"They."

Dalgard who had been a hunter and a tracker before he was an explorer crouched for a clearer view. Yes, they were recent, yet not made today or even yesterday; there was a thin film of dust resettled in each.

"Some days ago. They are not in the city now," the merman declared with certainty. "But they will come again."

"How do you know that?"

Sssuri's hand swept about to include the wealth around them. "They have taken some, perhaps to them the most needful. But they will not be able to resist gathering the rest. Surely they will return, perhaps not once but many times. Until—"

"Until they come to stay." Dalgard was grim as he completed that sentence for the other.

"That is what they will work for. This land was once under their mastery. This world was theirs before they threw it away warring among themselves. Yes, they dream of holding all once more. But"—Sssuri's yellow eyes took on some of the fire which had shone in those of the snake-devil during its last seconds of life—"that must not be so!"

"If they take the land, you have the sea," Dalgard pointed out. The mermen had a means of escape. But what of his own clansmen? Large families were unknown among the Terran colonists. In the little more than a century they had been on this planet their numbers, from the forty-five survivors of the voyage, had grown to only some two hundred and fifty, of which only a hundred and twenty were old enough or young enough to fight. And for them there was no retreat or hiding place.

"We do not go back to the depths!" There was stern determination in that declaration from Sssuri. His tribe had been long hunted, and it wasn't until they had made a loose alliance with the Terran colonists that they had dared to leave the dangerous ocean depths, where they were the prey of monsters more ferocious and cunning than any snake-devil, to house their families in the coast caves and on the small islands off-shore, to increase in numbers and develop new skills of civilization. No, knowing the stubbornness which was bred into their small, furry bodies, Dalgard did not believe that many of the sea people would willingly go back into the sunless depths. They would not surrender tamely to the rulership of the loathed race.

"I don't see," Dalgard spoke aloud, half to himself, as he studied the tables closely packed, the machines standing on bases about the walls, the wealth of alien technology, "what we can do to stop them."

The restriction drilled into him from early childhood, that the knowledge of Those Others was not for his race and in some way dangerous, gave him an uneasy feeling of guilt just to be standing there. Danger, danger which was far worse than physical, lurked there. And he could bring it to life by merely putting out his hand and picking up any one of those fascinating objects which lay only inches away. For the pull of curiosity was warring inside him against the stern warnings of his Elders.

Once when Dalgard had been very small he had raided his father's trip bag after the next to the last exploring journey the elder Nordis had made. And he had found a clear block of some kind of greenish crystal, in the heart of which threadlike lines of color wove patterns which were utterly strange. When he had turned the block in his hand, those lines had whirled and changed to form new and intricate designs. And when he had watched them intently it had seemed that something happened inside his mind and he knew, here and there, a word, a fragment of alien thought—just as he normally communicated with the cub who was Sssuri or the hoppers of the field. And his surprise had been so great that he had gone running to his father with the cube and the story of what happened when one watched it.

But there had been no praise for his discovery. Instead he had been hurried off to the chamber where an old, old man, the son of the Great Man who had planned to bring them across space, lay in his bed. And Forken Kordov himself had talked to Dalgard in his old voice, a voice as withered and thin as the hands crossed helplessly on his shrunken body, explaining in simple, kindly words that the knowledge which lay in the cubes, in the oddly shaped books which the Terrans sometimes came across in the ruins, was not for them. That his own great-grandfather Dard Nordis, who had been one of the first of the mutant line of sensitives, had discovered that. And Dalgard, impressed by Forken, by his father's concern, and by all the circumstances of that day, had never forgotten nor lost that warning.

"We cannot hope to stop them," Sssuri pointed out. "But we must learn when they will come again and be waiting for them—with your people and mine. For I tell you now, brother of the knife, they must not be allowed to rise once more!"

"And how can we foretell their coming?" Dalgard wanted to know.

"Perhaps that alone we cannot do. But when they come they will not leave speedily. They have stayed here before without harm, and their distrust has been lulled. When next they come, it will be only according to their natures that they will wish to stay longer. Not snatching up the closest to hand of these treasures of theirs, but choosing out with care those things which will give them the best results. Therefore they may make a camp, and we can summon others to aid us."

"To return to Homeport will take several days even if we push," pointed out the scout.

"Word can pass swifter than man," the merman returned, with confidence in his own plan of action. "We shall put other eyes, other ears, many eyes, many ears, to service for us. Be assured we are not the only ones to fear the return of Those Others from overseas."

Dalgard caught his meaning. Yes, it would not be the first time the hoppers and other small animals living in the grasslands, the runners and even the moth birds that only the mermen could mind touch, would relay a message across the land. It might not be an accurate message—to transmit that by small animal brains was impossible—but the meaning would reach both merman and colony Elders: trouble in the north, help needed there. And since Dalgard was the only explorer at present who had chosen the northern trails, his people would know that he had sent that warning and would act upon it, as Sssuri's message would in turn be heeded by the warriors of his tribe.

Yes, it could be done. But what of the traces they had left here—the slaughtered snake-devils—?

Sssuri had an answer for that also. "Let them believe that one of my race came here, or that a party of us ventured to explore inland. We can make it appear that way. But they must not know of you. I do not believe that they ever learned of you or how your fathers came from the sky. And so that may swing the battle in our favor if it comes to open warfare."

What the merman said was sensible enough, and Dalgard was willing to obey orders. As he left the storehouse, Sssuri trailed him, scuffing each dusty print the scout left. Perhaps a master of trailcraft could unravel that spoor, but the colonist was ready to believe that no such master existed in the ranks of Those Others.

In the outer hall the merman approached the now dead snake-devil and jerked from its loose skin the arrow which had killed it. Loosing the head of his ruined spear from his belt, he dug and gouged at the small wound, tearing it so that its original nature was concealed forever. Then they retraced their way through the underground passages until they reached the sanded arena. Already insects buzzed hungrily about the hulks of the dead monsters.

There was a shrill squeal as the remaining infant reptile fled from the pouch where it had hidden. Sssuri hurled his knife, and the blade caught the small devil above the shoulder line, half cutting, half snapping its tender neck, so that it bounded aimlessly on to crash against the wall and fall back squirming feebly.

They collected the darts which had killed the others. Dalgard took the opportunity to study those bands on the forearms of the adults. To his touch they had the slick smoothness of metal, yet he was unfamiliar with the material. It possessed the ruddy fire of copper, but through it ran small black veins. He would have liked to have taken one with him for investigation, but it was out of the question to pry it off that scaled limb.

Sssuri straightened up from his last gruesome bit of stage-setting with a sigh of relief. "Go ahead." He pointed to one of the other archways. "I will confuse the trail."

Dalgard obeyed, treading as lightly as he could, avoiding all stretches in which he could leave a clear print. Sssuri ran lightly back and forth mixing the few impressions to the best of his ability.

They backtracked to the river, retrieved the boat and recrossed, to leave the city behind and strike into the open country beyond its sinister walls. Night was falling, and Dalgard was very glad that he was not to spend the time of darkness within those haunted buildings. But he knew that it was more than a dislike for being shut up in the alien dwellings which had brought Sssuri out into the fields. The second part of their plan must be put into operation.

While Dalgard willed his body motionless, the merman lay relaxed upon the ground before him as he might have floated upon his beloved waves in some secluded cove. His brilliant eyes were closed. Yet Dalgard knew that Sssuri was far from asleep, and with all his own power he tried to join in the broadcast: that urgency which should send some hopper, some night runner, on to spread the rumor that there was trouble in the north, that danger existed and must be investigated. They had already met one colony of runners ranging southward to escape. But if they could send another such tribe traveling, arouse and aim south a hopper exodus, the story would spread until the fringe would reach the animals who lived in peace within touch of Homeport.

The sun was gone, the dark gathered fast. Dalgard could not even see the clustered buildings of the city now. And since he lacked Sssuri's range and staying power, he had no idea whether their efforts had met with even a shadow of success. He shivered in the bite of the wind and dared to lay his hand on Sssuri's shoulder, feeling anew the electric shock of warmth and bursting life which was always there.

Having so broken the other's absorption he asked a question: "Would it not be well, brother of the knife, if with the rising sun you returned to the sea and struck out to join your tribesmen, leaving me here to watch until you return?"

Sssuri's answer came with a speed which suggested that he, too, had been considering that problem. "We shall see what happens with the sun's rising. It is true that in the sea I can travel with greater speed, that there are hunting parties of my people striking into these waters. But they will not come to this city without good reason. It is an accursed place."

With the early morning the city drew them once more. Dalgard's curiosity pulled him to that storehouse. He could not stifle the hope that with luck he might find something there which would solve their problem for them. If there could only be a way to avoid open conflict with Those Others, some solution whereby the aliens need never know of the existence of the Colony. For so many generations, even centuries, the aliens had been confined, or had confined themselves, safely overseas on the western continent. Perhaps if now they were faced by some new catastrophe, they would never attempt to come east again. He had visions of discovering and activating some trap set to protect their treasures which could be turned against them. But he realized that he lacked the technical knowledge which would have aided him in the search for such a weapon.

The remnants of Terran science and mechanics, which the outlaws had brought with them from their native world, had been handed on; the experiments they had managed since with crude equipment had been carefully recorded, and he was acquainted with the outlines of most of them. But the few destructive arms they had imported were long since worn out or lacked charges, and they had not been able to duplicate them. Just as they had torn asunder the ship in which they had crossed space, to use its parts for the building of Homeport, so had they hoarded all else they had brought. But they were limited by lack of materials on Astra, and their fear of the knowledge of the aliens had kept them from experimenting with things found in the ruins.

There might be hundreds of objects on the shelves of that storage place, which, properly used, would reduce not only just the room and its contents to glowing slag, but take half the city with it. But he had no idea which, or which combination, would do it.

And here Sssuri could be no help. The mermen had made great strides forward in biological and mental sciences, but mechanics was a closed section of learning because of their enforced habitat under the sea, and of machines they knew less than the colonists.

"I have been thinking—" Sssuri broke into his companion's chain of reasoning, "of what we may do. And perhaps there is a way to reach the sea more swiftly than by returning overland."

"Downriver? But you said that way may have its watching devices."

"Which would be centered on objects coming upstream, not down. But in this city there should be yet another way—"

He did not enlarge upon that, but since he apparently knew what he was doing, Dalgard let him play guide once more. They recrossed the sluggish river, the scout looking into its murky depths with little relish for it as a means of transportation. Though it had an oily, flowing current, there was a suggestion of stagnant water with unpleasant surprises waiting beneath its turgid surface.

For the second time they entered the arena. Avoiding the bodies, Sssuri made a circuit of the sanded floor. He did not turn in at the archway which led to the storage place, but paused before another as if there lay what he had been searching for.

Dalgard's less sensitive nostrils picked up a new scent, the not-to-be-missed fetor of damp underground ways where water stood. The merman edged around a barred gate as Dalgard sniffed again. The smell of damp was crossed by other and even less appetizing odors, but he did not catch the stench of the snake-devils. And, relying on Sssuri's judgment, he followed the merman into the dark.

Once again patches of violet light glimmered over their heads as the passage narrowed and sloped downward. Dalgard tried to remember the general geography of the section which was above them now. He had assumed that this way with its dank chill must give on the river. But when they had pattered on for a long distance, he knew that either they had passed beneath the stream or that he was totally lost as to direction.

As their eyes adjusted to the gloom of the passage the violet light grew stronger. So Dalgard saw clearly when Sssuri whirled and faced back along the way they had come, his body in a half crouch, his knife ready in his hand.

Dalgard, his bow useless in the damp, drew his own sword-knife. But, though his mind probed and he listened, he could sense or hear nothing on their trail.