The lightning lasted for seconds at a time, and at such times the scene stood for all that was barbarous and fantastic. The dark, mysterious river flowed upon its course through the narrow gorge where the lightning beat upon the rocks. The electricity in the air flashed, died out, and flashed again, like thousands of sparks in the wind. And there, upon the white sand, writhing in torture, were the dark forms of those who had been stricken by the pestilence.

Max had never felt so powerless. He was in the heart of the Unknown.

Close at hand, lay those who had been stricken by a force which all the resource of modern science had entirely failed to conquer. Overhead, echoed and mirrored by the rocks, the typhoon rent the sky with sheets of fire, whilst peal upon peal of thunder caused the earth to tremble.

Yet Max was by no means disposed to forget the object of his quest. He was determined to find out the nature of the work which was carried on at the quarry. He hastened forward, and presently blundered into one of the great heaps of sifted debris.

He picked up a handful of this and examined it in the light of the lightning. As far as he could make out, it was composed of a kind of fine gravel, in which appeared great quant.i.ties of a green stone, known as serpentine.

Being unable to find out anything definite from the heaps of debris, he resolved to examine the quarry. The wind was too great to permit him to strike a match, even had that been prudent. He was obliged to rely upon the lightning to guide him in his search. He availed himself of the opportunity of a series of flashes to run to the quarry, and there he found himself in impenetrable darkness.

He stood waiting for the lightning to return. It seemed that the storm was already pa.s.sing. These tropical hurricanes, that often uproot the trees of the forest, are seldom of long duration. They are too violent to last for many minutes.

Max was beginning to think that the storm was pa.s.sed, when the sky immediately overhead burst into a lurid glow, and almost simultaneously a deafening peal of thunder rolled across the valley. Max leaned forward to examine the face of the rock; and as he did so, he was seized suddenly from behind.

As quick as thought, he whipped his revolver from its holster; and immediately the weapon was struck from his hand.

The lightning still continued, jumping like fire-light; and Max was able to make out the dark eyes and the pointed beard of Caesar.

The Portuguese was aided by an Arab. The struggle that ensued was no more than an affair of seconds. Max, though he fought with the strength that comes of desperation, was overpowered from the first, and presently he was thrown violently to the ground. There his hands were tied fast behind his back. Caesar was heard to laugh.

"Get up," said he, and then ran on in his broken English: "You must think me a fool, if I do not keep a sentry by night over the richest of my possessions. Come, follow me."

He led the way across the bridge, and Max had no alternative but to obey him. The Arab, rifle in hand, brought up the rear.

They pa.s.sed around the eastern sh.o.r.e of the lake, walking on the crisp sand in which their boots sank to the ankles. Max saw the kraal wherein the man's slaves were asleep; and a few minutes afterwards they came to the stockade. Caesar led the way into his hut--the hut in which Crouch and he had played cards some weeks before. He told Max to sit down upon a chair, and placed himself on the other side of the room, with his loaded revolver ready to his hand.

"If you endeavour to escape," said he, "I shoot. I advise you to remain still, and listen to what I have to say."

Max looked about him. As far as he could see there was no method of escape. His wrists had been bound securely.

"In the first place," said Caesar, "I would like to know for what reason you have meddled in my affairs."

"You are a slave-dealer," said Max.

"That may, or may not, be true."

"It is true," cried the young Englishman, his anger rising in a flood.

"I know it. The employment of slaves is a sin in the eyes of both G.o.d and man. Justice is the duty of every one; and that is why we have meddled--as you call it--in your affairs."

"I have already pointed out," said Caesar, "that the laws of civilization do not apply to Makanda. But that is beside the mark. I understand you are a doctor, that you have had some sort of medical training."

Max answered that that was so.

"Do you understand the treatment of cholera?"

"I know the various methods that have been tried," said Max; "but, as you probably know, they are seldom successful."

It was at that moment that Max heard a loud groan which issued from a hut not far away.

"Do you hear that?" asked Caesar.

Max nodded his head.

"That is my friend, de Costa. When he returned to the stockade this evening he was taken ill with cholera. I went to look at him an hour ago, just before my sentry informed me that you were in the quarry. He is dying."

"How does that concern me?" asked Max.

"It concerns you," answered Caesar, "inasmuch as it concerns myself. Your life is in my hands. I can either kill you, or place an iron collar around your neck and yoke you to a gang of slaves. If you do not do as I wish, I will have you shot. If you obey me, you may continue to live--as a slave."

"What is it you want?" asked Max.

"I want you to do what you can to save de Costa. He is of some use to me. Indeed, I could not do very well without him."

"I will do what I can," said Max.

Outside, the Arab was on guard. Caesar lead the way to de Costa's hut; and there, Max found the half-caste stretched upon his bed, with features drawn and haggard, and his complexion of a ghastly purple hue.

His body was all twisted in his agony. He was too far gone to speak.

"Now," said Caesar, "I do not feel disposed to untie your hands; but you will kindly look at the bottles of medicine on that shelf, and see if you can find anything that might be of use."

Max searched the shelf where the half-caste kept his stock of drugs, and had no difficulty in finding the very thing he wanted, namely, opium.

He found also bis.m.u.th and nitrate of silver. He instructed Caesar how to mix these drugs in the ordained proportions; and the Portuguese placed a gla.s.s containing the medicine at the sick man's bedside. It is noteworthy that he took care not to touch the patient, for the disease is one of the most contagious in the world.

"Will he live, do you think?" asked Caesar.

"It is impossible to say," said Max.

"You can do nothing else?"

"Absolutely nothing. He has reached the turning point. If he does not die in an hour or so, he will live."

"Come," said Caesar, "we must not risk contagion."

Outside the hut he paused, and spoke to the Arab, who immediately left the stockade. He then ordered Max to enter his hut, and followed with his loaded revolver in his hand.

"You have come to spy out my secrets," said he. "You are at liberty to learn as much as you wish. It can make no difference to me; for I intend that you shall never see Europe again."

So saying, he drew a bunch of keys from his pocket, and stepped to the great, padlocked chest on the other side of the room. One by one, he unlocked the padlocks, and then threw back the lid, and stood by, holding the candle over the contents.

"Here," said he, "see for yourself. Few have ever witnessed such a sight."

Max drew nearer, and looked down into the box. For some seconds he stood as if spellbound, unable to move his gaze. The chest was about three-quarters full of the most enormous Oriental rubies.

Caesar took one at random, and held it before the light. Garnets had been found in Africa, and even spinels; but these were genuine rubies of the highest quality, such as had hitherto only been discovered in the famous mines of Ava.

CHAPTER XVII--THE TABLES TURNED