THE great snake's head and long slender neck glistened in the morning sun as it stood above the tops of the waving reeds and the softly rattling cane stalks of the great swamp. Slowly with a smooth, pendulous, weaving motion it swayed from side to side as its cold green eyes peered toward the tree into which Og and Ru had taken refuge. Its darting tongue flashed inquisitively in and out between the cruel, thin, scaly lips of its powerful jaws, and it seemed to pause there as if trying to make up its mind just what to do. Then suddenly, soundlessly, like a flash the head disappeared, and Og and his companion huddled in the branches of the big tree into which they had taken refuge knew instinctively that the snake had seen them and that it was sliding swiftly and silently toward them.
They could see the undulating movement in the reeds as the long, slender body moved its serpentine way in their direction. It was like the coming of relentless, hideous doom, and both of the Hairy Boys shivered with fear and consternation, for in their mad and hurried scramble at first catching sight of the great snake they had climbed into the tree nearest to them not paying much attention to the fact that while it was a big tree, it stood to a certain extent alone. The other trees about it were too far away for them to swing from branch to branch across the intervening space, and now they were cornered; marooned, as it were, in that one tree and their only chance of getting away would be to drop back to the ground again and dash for another tree. But now the big snake was too close for them to do even that.
On came the snake, swiftly, silently save for the sickening sound of its long scaly body dragging through the marsh growth. Og and Ru looked at each other and each knew that the other felt that death was close upon him. But Og, ever valiant, and perhaps with better control of his fears and emotions than Ru, grunted words of encouragement to his companion and gripping his stone hammer more securely indicated that he did not intend to yield without a struggle.
Closer drew the serpent. They could see the great undulating folds of its mottled green and black and brown body among the reeds now, but the ugly flat head remained hidden as it pushed its way through the tangle of undergrowth. Then suddenly it came into the opening where reeds and cane and all other vegetation had been trampled down, or uprooted by the death struggle of the hairy mammoth, and there it paused a moment while it raised its head and shining neck and peered up into the foliage of the tree where Og and Ru crouched trembling against the swelling trunk. For many horror-fraught seconds it hesitated there and the Hairy Boys saw by the cold, wicked gleam in its green eyes, that it had marked them for its prey. But they saw too that despite its great size and tremendous strength the snake was cautious. It did not intend to take any needless risk in getting them. Og and Ru sensed this caution and Og's brain, ever working, found a measure of encouragement in its hesitation.
Perhaps he could make it fear him enough to have it decide to give over the attack and go peacefully on its way. He began to frown and make ugly faces and brandish his stone hammer belligerently. He even began to call the great snake names; ugly names. He reviled it and hurled imprecations and threats at it. He even warned it that he would come down out of the tree and kill it if it did not go away. In his heart he knew this was idle boasting, but somehow it seemed the natural, human thing to do, for he sensed that if he could make himself appear big and formidable he might be able to make the snake fear him as much as he feared the snake. Ru looked at Og and marveled at what he heard him say. And then because Og appeared so big and brave Ru took heart too. With Og's bluffing both of them gained courage.
But of course their threats were nothing but so much noisy chatter to the great snake. The reptile hesitated only because it sensed a difference between these two Hairy Boys, and the people who always lived in the trees; the Tree People-apes  who were its natural prey. The serpent had often lain in waiting, its ugly length draped and hidden among the lianas that intertwined among the trees of the forest, lurking thus until some wandering band of Tree People came trooping noisily by. Then it would strike among them and whipping its great body about one of them crush out its life while the others scattered chattering through the forest. But the great snake knew that these two were different; they were not Tree People, they were the people who lived in the cliff caves. But it feared them not much more than it feared the Tree People; for when it was really hungry and food was hard to find it had more than once made a nocturnal visit to the cliff dwellings and dragged one of these men kicking and struggling and screaming from his cave, crushing it and devouring it with little more trouble than it did a goat or a three-toed horse. And it was hungry now, and hunting food, and here was all it wanted for one meal cornered and trembling with fear and only needed to be captured.
The great snake, had apparently made up its mind what to do for presently it began to slide toward the trunk of the tree, and Og and Ru, seeing this, and realizing that their threats and boasting had been in vain, began to scramble higher among the branches. Unhurried, slowly, relentlessly the snake began to climb. It reached its ugly flat head and scaly neck along the tree trunk until it slid part of its body over one of the lower branches. Then it climbed more swiftly, weaving from branch to branch and draping its scaly folds among them as it made its way upward.
Higher and higher climbed Og and Ru. They were getting into the very top now where the branches were the thickness of their wrists and smaller. The top was swaying under their weight and the leaves rustled as if in a wind storm. But they knew that as high as they climbed the snake would eventually reach higher and pull them down for it was in its element, and they could go nowhere in the tree that it could not follow them.
Suddenly Ru stopped as if to think a moment. Then with an exclamation he pointed to where, lower down and on the other side of the trunk one limb a little longer than all the rest reached out until it's leaves and smaller twigs intertwined with an adjacent tree. There was just one chance of escape that way. If they could run out onto that branch and leap safely into the next tree they could get away for they knew they could travel much faster among the trees than the snake could. Ru determined to take that one chance and shouting for Og, who was higher up, to follow him he swung down toward the long branch and onto it. But he reached it just as the snake's head curled over it where the branch joined the trunk, and Og who was above them realized with a sickening feeling that he was cut off; that the snake was between him and escape and that Ru had successfully reached the branch that might be the pathway deeper into the forest.
For an instant the snake and the two Hairy Boys hesitated, Og in the tree top, Ru on the swaying branch and the snake between them, looking at first one and then the other with his cold evil eyes. It was as if the reptile was trying to make up his mind which one to pursue. Then perhaps because Ru was the nearest, for he stood balancing uncertainly on the limb which proved to be not as thick and strong as he hoped, the snake decided that he was the one he would make a meal of for he ceased his climbing then and began to slide his big flat ugly head and scaly length slowly out onto the branch on which Ru stood.
With a scream of terror, Ru ran out onto the branch until it began to bend and sway perilously under his weight. And then he discovered to his horror that the limb sagged far down and that the space between himself and the other tree was far too great for him to leap across. He was cornered indeed.
Turning, with horror and the fear of death in his eyes, he faced the great snake moving slowly out onto the branch toward him. Sitting astride the swaying branch and gripping it with his feet and one free hand he waited; waited for death  a terrible death. But he waited with his fist clenched grimly about his upraised stone hammer, determined to strike as soon as the snake's head came within striking distance. And the snake seeing his threatening attitude raised its head and long neck swanlike and arched it above him just out of reach of his stone hammer, but still moving slowly toward him, with terrible jaws open and long gleaming teeth distended, ready to strike from above and encompass his whole head in its cavernous mouth. Ru sick and trembling with fear and nauseated with the stench that came to him as he felt the hot breath of the serpent in his face, stared up at the snake as if paralyzed by the awful doom that hung over him.