smiling man was anxious to learn which way the other safari had gone, and was hoping that Biff’s change of manner would give the fact away.

Suddenly, there came an interruption that gave Biff a cause for real alarm.

“Listen!” he exclaimed.

From the treetops came a running chatter that seemed to carry like a wave from somewhere off in the jungle. Biff recognized the excited gabble.

“The howler monkeys!” he told Serbot. “That’s the way they acted after the Macus shot some of them with arrows yesterday!”

Serbot tried to gauge the direction of the sound, then ordered the safari onward, faster. They followed the rough, irregular trail until they reached a spot where the chatter lessened and finally quieted altogether. Serbot waved for the bearers to set down their packs.

The order came just in time. The bearers themselves pointed to heads and shoulders that bobbed from behind trees and bushes. Terrified, the bearers shouted, “Macu!”

Serbot dived behind a pack, to use it as a shelter. Pepito and Urubu did the same, expecting Biff to join them with the huddling bearers, for spears, arrows, and darts were now skimming toward them. Instead, Biff acted upon sudden impulse and raced along the jungle trail. He heard guns blast in back of him, but knew Serbot and the others were too busy shooting at the attacking head-hunters to worry about him.

Biff passed a turn in the trail and knew then that he was safe from gunfire, but he had his eye on an opening in the jungle another hundred feet ahead. There, Biff was sure that he could duck from sight the way Kamuka had. But Biff was becoming too hopeful too soon.

Less than halfway to the spot, Biff halted in his tracks as the foliage parted and a painted Macu warrior loomed in sight. Armed with bow and arrow, the deadly marksman was already taking aim at Biff with his bowstring fully drawn.

Another moment, and the poison-tipped arrow would be in flight, allowing Biff no chance of escape at such close range!

CHAPTER XIII The River of Death

CHAPTER XIII

The twang of the head-hunter’s bowstring was drowned by an explosive burst from farther up the trail. With it, the Macu marksman gave an upward, sideward jolt at the very instant the arrow was leaving his 

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