Waldo watched him out of sight, half minded to follow, for he was far from satisfied that the fellow had been entirely honest with him. Why he should have been otherwise Waldo could not imagine, but nevertheless there had been an indefinable suggestion of duplicity in the man's behavior that had puzzled him.

However, Waldo took up his search toward the west, passing down from the hills into a deep valley, the bottom of which was overgrown by a thick tangle of tropical jungle. He had forced his way through this for nearly half a mile when he came to the bank of a wide, slow-moving river. Its water was thick with sediment--not clean, sparkling, and inviting, as were the little mountain streams of the hills and valleys farther south.

Waldo traveled along the edge of the river in a northwesterly direction, searching for a ford. The steep, muddy banks offered no foothold, so he dared not venture a crossing until he could be sure of a safe landing upon the opposite shore. A couple of hundred yards from the point at which he had come upon the stream he found a broad trail leading down into the water, and on the other side saw a similar track cutting up through the bank.

This, evidently, was the ford he sought, but as he started toward the river he noticed the imprints of the feet of many animals--human and brute.

Waldo stooped to examine them minutely. There were the broad pads of Nagoola, the smaller imprints of countless rodents, but back and forth among them all were old and new signs of man. There were the great, flat-foot prints of huge adult males, the smaller but equally flat-footed impresses of the women and children; but one there was that caught his eye particularly.

It was the fine and dainty outline of a perfect foot, with the arch well defined. It was new, as were many of the others, and, like the other newer ones, it led down to the river and then back again, as though she who made it had come for water and then returned from whence she had come. Waldo knew that the tracks leading away from the river were the newer, because where the two trails overlapped those coming up from the ford were always over those which led downward.

The multiplicity of signs indicated a considerable community, and their newness the proximity of the makers. Waldo hesitated but a moment before he reached a decision, and then he turned up the trail away from the river, and at a rapid trot followed the spoor along its winding course through the jungle to where it emerged at the base of the foothills, to wind upward toward their crest.

He found that the trail he was following crossed the hills but a few yards from the spot at which he had met the cave man a short time before. Evidently the man had been returning from the river when he had espied Waldo.

The young man could see where the fellow's tracks had left the main trail, and he followed them to the point where the man had stood during his conversation with Waldo; from there they led toward the east for a short distance, and then turned suddenly north to reenter the main trail.

Waldo could see that as soon as the man had reached a point from which he would be safe from the stranger's observation he had broken into a rapid trot, and as he already had two hours' start Waldo felt that he would have to hurry were he to overtake him.

Just why he wished to do so he did not consider, but, intuitively possibly, he felt that the surly brute could give him much more and accurate information than he had. Nor could Waldo eliminate the memory of those dainty feminine footprints. It was foolish, of course, and he fully realized the fact; but his silly mind would insist upon attributing them to the cave girl--Nadara.

For two hours he trotted doggedly along the trail, which for the most part was well defined. There were places, of course, which taxed his trailing ability, but by circling widely from these points he always was able to pick up the tracks again.

He had come down from the hills and entered an open forest, where the trail was entirely lost in the mossy carpet that lay beneath the trees, when he was startled by a scream--a woman's scream--and the hoarse gutturals of two men, deep and angry.

Hastening toward the sound, Waldo came upon the authors of the commotion in a little glade half hidden by surrounding bushes.

There were three actors in the hideous tragedy--a hairy brute dragging a protesting girl by her long, black hair and an old man, who followed, protesting futilely against the outrage that threatened the young woman.

None of them saw Waldo as he ran toward them until he was almost upon them, and then the beast who grasped the girl looked up, and Waldo recognized him as the same who had sent him toward the west earlier in the day.

At the same instant he saw the girl was Nadara. In the brief interval that the recognition required there sloughed from the heart and mind and soul of Waldo Emerson Smith-Jones every particle of the civilization and culture and refinement that had required countless ages in the building, stripping him naked, age on age, down to the primordial beast that had begot his first human progenitor.

He saw red through blood as he leaped for the throat of the man-beast whose ruthless hands were upon Nadara. His lip curled in the fighting snarl that exposed his long-unused canine fangs.

He forgot sword and shield and spear.

He was no longer a man, but a terrible beast; and the hairy brute that witnessed the metamorphosis blanched and shrank back in fear. But he could not escape the fury of that mad charge or the raging creature that sought his throat.

For a moment they struggled in a surging, swaying embrace, and then toppled to the ground--the hairy one beneath. Rolling, tearing, and biting, they battled--each seeking a death hold upon the other.

Time and again the gleaming teeth of the once-fastidious Bostonian sank into the breast and shoulder of his antagonist, but it was the jugular his primal instinct sought.

The girl and the old man had drawn away where they could watch the battle in safety. Nadara's eyes were wide in fascination.

Her slim, brown hands were tight pressed against her rapidly rising and falling breasts as she leaned a little forward with parted lips, drinking in every detail of the conflict between the two beasts.

Ah, but was the yellow-haired giant really fighting for possession of her, or merely in protection, because she was a woman?

She could readily conceive from her knowledge of him that he :night be acting now solely from some peculiar sense of duty which she realized that he might entertain, although she could not herself understand it.

Yes, that was it, and when he had conquered his rival he would run away again, as he had months before. At the thought Nadara felt herself flush with mortification. No, he should never have another opportunity to repeat that terrible affront.

As she allowed her mind to dwell on the humiliating moment that had witnessed the discovery that Thandar had fled from her at the very threshold of her home Nadara found herself hating him again as fiercely as she had all these long months--a hatred that had almost dissolved at sight of him as he rushed our of the underbrush a moment before to wrest her from the clutches of her hideous tormentor.

Waldo and his antagonist were still tearing futilely at one another in mad efforts to maim or kill. The giant muscles of the cave man gave him but little if any advantage over his agile, though slightly less-powerful, adversary.

The hairy one used his teeth to better advantage, with the result that Waldo was badly torn and bleeding from a dozen wounds.

Both were weakening now, and it seemed to the girl who watched that the younger man would be the first to succumb to the terrific strain under which both had been. She took a step forward and, stooping, picked up a stone.

Her small strength would be ample to turn the scales as she might choose--a sharp blow upon the head of either would give his adversary the trifling advantage that would spell death for the one she struck.

The two men had struggled to their feet again as she approached with raised weapon.

At the very moment that it left her hand they swung completely round, so that Waldo faced her, and in the instant before the missile struck his forehead he saw Nadara in the very act of throwing--upon her face an expression of hatred and loathing.

Then he lost consciousness and went down, dragging with him the cave man, upon whose throat his fingers had just found their hold.