if any further proof were needed of the delicacy and danger of the situation of the white men, it came the next minute, when, as they were in the act of stepping back into the trail, the sailor caught the arm of his friend and checked him.

no need of speaking, for ashman had detected the peril at the same instant.

two natives were stealing like phantoms along the path, from the direction of the river and going toward the village.

had they been ten seconds later, the foremost would have collided with the young explorer.

the latter held his breath, and placed his hand on his revolver, believing a fight was inevitable.

so it would have been, had not the attention of the savages been absorbed by the scene in the square, of which they caught sight a pace or two before coming opposite the watchers.

they strode directly onward, and swung across the open space, swerving enough to one side to avoid the struggling lines, and moving on until they reached the fringe of spectators beyond. there they could no longer be identified, and probably took their places among those who were enjoying the cruel spectacle.

ashman waited a brief while beside the path, fearful that other natives might be coming; but, when the minutes passed without their appearance, he resumed picking his way back, and quickly stood erect in the narrow opening, which he felt had been followed too far from the xingu.

there was no reason to suspect that any of the natives knew of the presence of the mysterious strangers so near them, but since they seemed to have a remarkable disposition to be on the move, our friends felt it would not be safe to relax their caution for a single instant.

while they did not apprehend a direct pursuit, there was a probability that some parties might be moving along the trail behind them, while they had seen enough to convince them of the danger from the front. ashman, therefore, whispered to his companion to keep special guard against an approach from the rear, while he would be equally alert in guarding the front.

the two kept so near that they could have reached each other by simply extending the hand.

they had no more than fairly started on their withdrawal from the spot, when johnston touched the arm of his friend, who instantly halted to learn the cause.

"i believe some of 'em are following us," said johnston.

fred listened, but his straining ear could detect nothing to warrant such an alarming conclusion, and he so stated.

the sailor became convinced that possibly he was mistaken. there is no law governing noises at night, and it might be that he had misjudged the rustling of a branch or possibly the stealthy footsteps of some wild animal.

not entirely convinced, however, that his companion was mistaken, fred once more resumed the advance, trying to perform the difficult task of giving as much attention to the rear as the front.

if the savages suspected the presence of others, they would be likely to tread so lightly that their footfalls could not be heard; but inasmuch as neither of the whites could believe they had even the most shadowy knowledge of them, they relied more on hearing than sight.

suddenly fred started and almost uttered an exclamation. in his nervous, apprehensive state, he was sure that one of their dusky foes had leaped from the side of the path and was crouching in front.

he drew his pistol and waited for the assault, which he was confident would come the next moment; but the seconds passed and all remained profoundly still.

with his weapon ready for instant use, he advanced a pace or two, touching the sailor as a command for him to remain motionless; but the chivalrous fellow would not obey, and was close behind him, when he stooped down and placed his hand on a piece of decayed limb that had fallen into the path.

"what a mistake," muttered fred, with a sigh, as he shoved it aside with his foot, explaining its nature to the wondering johnston.

but it was only simple prudence to maintain unceasing vigilance, and he did not permit the error to lessen his watchfulness. it was rather the reverse.

but the explorers were threading their way through a labyrinth of peril, the like of which they had never encountered before.

fred had not gone a hundred yards further, when his companion once more caught his arm, and he turned about as before to learn the cause.

"what have you heard?" he asked, with his mouth almost against the ear of the other.

"there are some of 'em behind us, certain sure!"

"how do you know there are more than one?"

"by the sound—there!"

the amazement of the two may be understood, when they not only detected the sound of footfalls, but discovered that instead of being at the rear as both thought, they were in front!

a party of natives were approaching from the xingu, and the keener hearing of johnston first discovered them.

the whites had stopped near a spot where a few rays of moonlight fell upon the trail, giving them a faint but needed view of the direction from which the danger threatened.

neither spoke again, but with the utmost care and noiselessness, they stepped aside from the path and crouched among the undergrowth.

they had barely time to ensconce themselves in their new position, when the footfalls sounded more distinctly than before, and something in the nature of an exclamation was heard from one of the approaching savages.

it sounded more like the grunt of a pig than anything the listeners could call to mind, and ashman feared it was notice of one warrior to his companions that he had discovered something amiss.

but if such were the fact, the natives would have stopped, while the cat-like steps were more audible than before, though the wonder to the watchers was that the parties continued invisible.

the eyes of both remained fixed on the faintly illuminated space, where they expected to catch sight of them, but the straining gaze failed to detect the most shadowy form.

ashman was just beginning to suspect some strange mistake had been made, when he suddenly saw the form of a tall savage with bushy head and a javelin in his hand, glide like a shadow into the darkness in front. a moment after, a second followed, then a third, fourth and fifth, the last carrying a long-bow, and all plainly seen by the whites at the side of the trail.

a few minutes later, fred once more took the advance, reflecting that they were as likely to meet more of the natives as to have them overtake them.

the mystery was where they had come from in the first place. they could not have entered the trail at the camp where ashman and johnston had started on their little exploring enterprise. it looked as though they were hiding among the trees at the time the canoe approached the land, and may have followed the explorers soon after they started along the path with the purpose of cutting off their retreat. if such should prove to be the case, fred felt that not only he and his companion were in danger, but all the rest were liable to be attacked by these natives, who, as has been stated, were the most athletic that had been encountered since leaving the amazon.

"fred," whispered the sailor a little later, "they've turned back and are following us again."

"are you sure of it?"

"there's no mistake about it."

fred was debating whether they should not turn again from the path, but he reflected that the natives having discovered the trick played on them, would be likely to defeat such a piece of strategy.

before he could decide upon the best course, johnston whispered:

"run! it's the only chance we've got!"