The ebon form of the Krooman giant seemed everywhere at once.
In the moonlight his terrible axe flashed incessantly and every time it fell a shriek or a muffled groan showed that it had found its fatal mark. The huge form of the warrior black seemed, however, to bear a charmed life. Again and again one of the attacking force would fire at him, but the bullets seemed to be warded off by some supernatural force. He was immune alike to bullets and arrows—with which latter the natives attached to Muley-Hassan's force battled.
Billy and Lathrop fought with unflinching courage, pouring out a leaden hail into the onslaught that again and again seemed as if it must drive the attacking force back. But fighting at such desperately uneven odds could not in the nature of things last long. There came a minute when Billy, turning to reload, found that before he could snatch up a handful of cartridges a huge Arab was on top of him.
Lathrop's clubbed rifle struck the fellow helpless the next minute and sent his long, cruel knife with a ringing crash to the floor.
Before Billy's half breathed "Thanks, old man," had left his lips, however, another of Muley-Hassan's followers had rushed in and the moment would have been Lathrop's last but that Billy drove his fist into the fellow's face with a crashing blow that knocked him on the top of his fallen comrade. It was hand-to-hand fighting then with a vengeance. Billy seized hold of the muzzle of an Arab's revolver as it was thrust into his very face, and twisted it upward as it was discharged. Seizing up a camp chair Lathrop swung it round his head like a club and scattered the brains of a native follower of Muley-Hassan.
But strategy was to put an abrupt end to the fight even if it could have continued much longer.
Billy was bleeding from a cut over the forehead which blinded him, and Lathrop had got two nasty knife thrusts, one in the arm and the other in the fleshy part of the calf of his leg, when they were suddenly attacked from the rear by half-a-dozen slavers. The next minute, wounded and bound, they were as helpless as two captured puppies.
The fight was over, but the Arabs had come out of it with a badly crippled force.
Of the twenty-five men who had attacked the adventurers' camp ten had been killed outright and half a dozen others so badly wounded that they could not move. Hardly one of them had not received some minor injury, and the very fact that they had made such a poor showing against two American boys and a Krooman armed only with an axe, filled Muley-Hassan with savage rage.
Furiously the slave-dealer ordered the two boys brought before him. A huge fire had been lighted by his followers and in the glare cast by this he received them. It was a wild scene and the two boys hardly knew whether they were awake or dreaming, as they were roughly hustled into the presence of their captor.
Diego de Barros, his cruel, thin lips curled in a sneer that showed his yellow teeth, stood by the side of Muley-Hassan, the latter a tall determined-looking man with a crisp, curly black beard and a sinister cast of features. A long burnoose of white, worn after the Arab style, hung from his head and framed his dark features, which were just then overspread by a frown as black as thunder.
Outside the circle of firelight lay the bodies of the victims of the Krooman's axe and the boys' bullets. All who could do so of Muley-Hassan's followers were gathered about him, as the two young Americans were brought face to face with the man they had such good reason to fear.
"So these are the young Americans?" he asked as Billy and Lathrop returned his hawk-like gaze unflinchingly.
"No, sir," spoke up Diego, "they are not. Wiseman has just told me that the Chester boys have flown in their air-ship and these are the cubs left behind to guard the camp."
At Wiseman's name mentioned in such a connection both the boys started.
"What! they have gone?" thundered the Arab chief.
"Yes, sir," stammered Diego, his coward nature aroused at the sight of his superior's fury.
"And by this time they are rifling the ivory cache. That fool Wiseman shall pay dearly for this. Bring him to me," shouted the Arab.
Desperate as was the boys' position they could not restrain a start of amazement as Professor Wiseman, his face pale as ashes to his very lips, came tremblingly forward.
"You were attached to this boys' camp to prevent by all means their sailing till I attacked the camp and made them prisoners, were you not?" demanded Muley-Hassan angrily.
Wiseman stammered something in reply.
"You are a coward as well as a fool," went on the slave-dealer, a cruel sneer breaking over his face; "but you have blundered for the last time. Take this fool away and kill him!" he ordered, turning away as if there was an end of the business.
Pitiful cries broke from the lips of the unhappy professor as he heard his death-warrant thus pronounced. He threw himself on his knees and begged and pleaded in a loud screeching tone for a little more time. But the chief was obdurate.
"Take him away," was all he said, and his men, not daring to disobey his orders any longer, fairly dragged the unfortunate prisoner toward the river bank. There was a short, sharp scream that chilled every drop of blood in the boys' bodies and then a splash. Professor Wiseman had paid the price of his treachery.
It was not till long after that the boys heard the full measure of his villainy. How posing as a naturalist he had wandered up and down the Ivory Coast for years acting as the secret agent of Muley-Hassan and making arrangements for the smuggling of slaves and illicitly procured ivory out of the country. He was too accomplished a rascal to be suspected and his learned appearance made it still more improbable that he should be engaged in any illegal trafficking. It was small wonder, too, that he had started when Frank mentioned the name of Luther Barr, for it was Luther Barr whom he had betrayed to Muley-Hassan and advised him of the whereabouts of the wily old New Yorker's ivory cache. As soon as he heard Frank mention the name he had of course surmised that the pretended hunting expedition was merely a blind to cover a bold dash to recover the ivory, though how they were to discover its whereabouts he could not imagine till, by prying and listening, he learned that they had a map of the locality of the stolen stuff.
He had then dispatched native canoe-men to Muley-Hassan and apprised him of the coming of the boys, and Diego had been at once sent out by the Arab to secure possession of the map if possible and, failing that, to destroy the boys' canoes. That the aeroplane would also have been put out of commission there is little doubt, if Diego or Wiseman could have found an opportunity. The brutal Arab could then have disposed of the expedition at his leisure. But the Golden Eagle II was too closely guarded for the two spies to be able to harm it.
The Kroomen porters attached to the camp had, as old Sikaso had forecast, fled into the jungle at the first attack of the Arab's followers and they did not put in an appearance till long after the marauders had left the camp.
But what puzzled the boys, as they stood facing the Arab with Professor Wiseman's scream still ringing in their ears, was "What had become of the old warrior."
He could not have turned traitor. His valiant behavior in the skirmish made that impossible to consider a minute. But it was equally certain that he was nowhere to be seen. What could have become of him? A dread that he was dead oppressed both boys as they stood there waiting for the Arab to speak.
Muley-Hassan seemed to be considering.
He twisted the ends of his jet-black mustaches like a man lost in thought, and the firelight playing on his bold reckless features showed there an expression of deep perplexity. But it was no question of mercy that was agitating his mind.
It was whether he would kill the boys right there or sell them into slavery.
To his money-making mind the latter idea commended itself. Two strong youths such as they were would fetch a good price anywhere, and so it came about that Billy and Lathrop—who had fully expected to share the Professor's fate—were flung by no gentle hands into their bullet-riddled tent and left to pass the night as best they could. Two men were posted to watch them and a rough cuff on the head rewarded Billy's single attempt to speak to Lathrop.
The next day at dawn the camp was the scene of great activity. The dead were carried into the forest a short distance and buried, while the wounded were attended to with such rough surgery as Muley-Hassan knew. In this work Diego, his lieutenant, who seemed to be a sort of Jack-of-all-trades—outside of his regular occupation of scoundrel—aided him; bandaging the cuts and extracting the bullets of his companions with some skill.
The boys were then given to eat some sort of stew in a big wooden basin and being just healthy American boys and not heroes of romance they ate heartily of the compound and felt better. Muley-Hassan himself examined the cut on Billy's forehead and Lathrop's two wounds and pronounced them mere scratches.
Just as it appeared that a start was about to be made the signal bell of the wireless rang. As our readers know it was Frank signaling from the Moon Mountains.
A sudden idea seemed to strike Diego at this. He called Muley-Hassan aside and talked earnestly with him for a few seconds, then he came up to the boy and demanded fiercely which one of them it was that understood wireless.
Lathrop replied that he did, and the next minute wished that he had bitten out his tongue before he had admitted it; for Diego, in a rough tone, ordered him to sit down at the instrument and reply that all was well at the River Camp.
"And, mind you, youngster—no tricks," he said savagely, "or I'll kill you as dead as mutton. I understand the Morse code myself and can tell what you are sending; and send slow so that I can get every letter."
Lathrop was in a quandary. To refuse to sit down at the instrument meant instant death.
He could tell that by the look in Diego's eyes and from what he had seen of him he knew he would not stop at a little thing like a murder to drive home a point.
The question was, did the man really understand telegraphy? If he didn't and was only, bluffing Lathrop determined to inform Frank of the true state of affairs. Otherwise it would do neither himself nor the others any good to try to trick Diego.
With a prayer on his lips that the Portuguese might not have been stating the truth about his knowledge of wireless the boy started to send. He had in his mind the message he would try to get through:
"We have been attacked. Get help and follow us."
But he had hardly tapped out with a hesitating finger the first word of his message when he felt a bullet whiz by his ear and the report flashed so close to him that it deafened him and scorched his skin.
"Thought I was bluffing did you, eh?" sneered the Portuguese, "come now, no tricks; send out what I tell you or the next bullet will come closer."
And so it came about that the queer hesitating message that Frank received at Moon Mountains was sent out.
Immediately it was dispatched Muley-Hassan gave the order to advance and his ragged followers, carrying the worst wounded in improvised litters, set out toward the northwest.
"We are going to the Moon Mountains," whispered Billy to Lathrop, "at least it looks that way. I overheard Muley-Hassan say to Diego that we'd have to hurry to get the ivory—"
Lathrop's reply was cut short by a scene that sent the angry blood to both boys' faces.
Before the camp was abandoned for good and the plunge into the forest began, Muley-Hassan gave a sharp order and directed several of his men set about demolishing the camp. Diego himself smashed the field wireless of which Frank and Harry had been so proud. He hacked it to atoms with one of the heavy axes. The tents and provision boxes were next piled in a heap and set in a blaze.
As the column of dark smoke rose from the ruins of the once happy camp into the clear sky the order to advance was given and the train once more moved forward.
They had hardly deserted the clearing before, from the river bank, half a hundred wild figures appeared.
They were similar in appearance—only even more wild-looking than the savages fought off by Frank, Harry and Ben the previous day. Like the others their slashed and scarred faces and clay-daubed lips showed them to belong to one of the fierce cannibal tribes of the Bambara region.
Their leader, a tall, thin savage of exceptionally repulsive appearance, motioned with his fingers to his thick lips for absolute silence among his followers.
Clutching their great broad-headed war-spears the next moment the savages slipped into the forest in the direction the Arab and his band had gone. Steadily they advanced with the quiet stealthy tread of panthers on the track of their prey.
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