Now I realized why the black pirate had kept me engrossed with his strange tale. For miles he had sensed the approach of succour, and but for that single tell-tale glance the battleship would have been directly above us in another moment, and the boarding party which was doubtless even now swinging in their harness from the ship's keel, would have swarmed our deck, placing my rising hope of escape in sudden and total eclipse.

I was too old a hand in aerial warfare to be at a loss now for the right manoeuvre. Simultaneously I reversed the engines and dropped the little vessel a sheer hundred feet.

Above my head I could see the dangling forms of the boarding party as the battleship raced over us. Then I rose at a sharp angle, throwing my speed lever to its last notch.

Like a bolt from a crossbow my splendid craft shot its steel prow straight at the whirring propellers of the giant above us. If I could but touch them the huge bulk would be disabled for hours and escape once more possible.

At the same instant the sun shot above the horizon, disclosing a hundred grim, black faces peering over the stern of the battleship upon us.

At sight of us a shout of rage went up from a hundred throats. Orders were shouted, but it was too late to save the giant propellers, and with a crash we rammed them.

Instantly with the shock of impact I reversed my engine, but my prow was wedged in the hole it had made in the battleship's stern. Only a second I hung there before tearing away, but that second was amply long to swarm my deck with black devils.

There was no fight. In the first place there was no room to fight. We were simply submerged by numbers. Then as swords menaced me a command from Xodar stayed the hands of his fellows.

"Secure them," he said, "but do not injure them."

Several of the pirates already had released Xodar. He now personally attended to my disarming and saw that I was properly bound. At least he thought that the binding was secure. It would have been had I been a Martian, but I had to smile at the puny strands that confined my wrists. When the time came I could snap them as they had been cotton string.

The girl they bound also, and then they fastened us together. In the meantime they had brought our craft alongside the disabled battleship, and soon we were transported to the latter's deck.

Fully a thousand black men manned the great engine of destruction. Her decks were crowded with them as they pressed forward as far as discipline would permit to get a glimpse of their captives.

The girl's beauty elicited many brutal comments and vulgar jests. It was evident that these self-thought supermen were far inferior to the red men of Barsoom in refinement and in chivalry.

My close-cropped black hair and thern complexion were the subjects of much comment. When Xodar told his fellow nobles of my fighting ability and strange origin they crowded about me with numerous questions.

The fact that I wore the harness and metal of a thern who had been killed by a member of my party convinced them that I was an enemy of their hereditary foes, and placed me on a better footing in their estimation.

Without exception the blacks were handsome men, and well built. The officers were conspicuous through the wondrous magnificence of their resplendent trappings. Many harnesses were so encrusted with gold, platinum, silver and precious stones as to entirely hide the leather beneath.

The harness of the commanding officer was a solid mass of diamonds. Against the ebony background of his skin they blazed out with a peculiarly accentuated effulgence. The whole scene was enchanting. The handsome men; the barbaric splendour of the accoutrements; the polished skeel wood of the deck; the gloriously grained sorapus of the cabins, inlaid with priceless jewels and precious metals in intricate and beautiful design; the burnished gold of hand rails; the shining metal of the guns.

Phaidor and I were taken below decks, where, still fast bound, we were thrown into a small compartment which contained a single port-hole. As our escort left us they barred the door behind them.

We could hear the men working on the broken propellers, and from the port-hole we could see that the vessel was drifting lazily toward the south.

For some time neither of us spoke. Each was occupied with his own thoughts. For my part I was wondering as to the fate of Tars Tarkas and the girl, Thuvia.

Even if they succeeded in eluding pursuit they must eventually fall into the hands of either red men or green, and as fugitives from the Valley Dor they could look for but little else than a swift and terrible death.

How I wished that I might have accompanied them. It seemed to me that I could not fail to impress upon the intelligent red men of Barsoom the wicked deception that a cruel and senseless superstition had foisted upon them.

Tardos Mors would believe me. Of that I was positive. And that he would have the courage of his convictions my knowledge of his character assured me. Dejah Thoris would believe me. Not a doubt as to that entered my head. Then there were a thousand of my red and green warrior friends whom I knew would face eternal damnation gladly for my sake. Like Tars Tarkas, where I led they would follow.

My only danger lay in that should I ever escape the black pirates it might be to fall into the hands of unfriendly red or green men. Then it would mean short shrift for me.

Well, there seemed little to worry about on that score, for the likelihood of my ever escaping the blacks was extremely remote.

The girl and I were linked together by a rope which permitted us to move only about three or four feet from each other. When we had entered the compartment we had seated ourselves upon a low bench beneath the porthole. The bench was the only furniture of the room. It was of sorapus wood. The floor, ceiling and walls were of carborundum aluminum, a light, impenetrable composition extensively utilized in the construction of Martian fighting ships.

As I had sat meditating upon the future my eyes had been riveted upon the port-hole which was just level with them as I sat. Suddenly I looked toward Phaidor. She was regarding me with a strange expression I had not before seen upon her face. She was very beautiful then.

Instantly her white lids veiled her eyes, and I thought I discovered a delicate flush tingeing her cheek. Evidently she was embarrassed at having been detected in the act of staring at a lesser creature, I thought.

"Do you find the study of the lower orders interesting?" I asked, laughing.

She looked up again with a nervous but relieved little laugh.

"Oh very," she said, "especially when they have such excellent profiles."

It was my turn to flush, but I did not. I felt that she was poking fun at me, and I admired a brave heart that could look for humour on the road to death, and so I laughed with her.

"Do you know where we are going?" she said.

"To solve the mystery of the eternal hereafter, I imagine," I replied.

"I am going to a worse fate than that," she said, with a little shudder.

"What do you mean?"

"I can only guess," she replied, "since no thern damsel of all the millions that have been stolen away by black pirates during the ages they have raided our domains has ever returned to narrate her experiences among them. That they never take a man prisoner lends strength to the belief that the fate of the girls they steal is worse than death."

"Is it not a just retribution?" I could not help but ask.

"What do you mean?"

"Do not the therns themselves do likewise with the poor creatures who take the voluntary pilgrimage down the River of Mystery? Was not Thuvia for fifteen years a plaything and a slave? Is it less than just that you should suffer as you have caused others to suffer?"

"You do not understand," she replied. "We therns are a holy race. It is an honour to a lesser creature to be a slave among us. Did we not occasionally save a few of the lower orders that stupidly float down an unknown river to an unknown end all would become the prey of the plant men and the apes."

"But do you not by every means encourage the superstition among those of the outside world?" I argued. "That is the wickedest of your deeds. Can you tell me why you foster the cruel deception?"

"All life on Barsoom," she said, "is created solely for the support of the race of therns. How else could we live did the outer world not furnish our labour and our food? Think you that a thern would demean himself by labour?"

"It is true then that you eat human flesh?" I asked in horror.

She looked at me in pitying commiseration for my ignorance.

"Truly we eat the flesh of the lower orders. Do not you also?"

"The flesh of beasts, yes," I replied, "but not the flesh of man."

"As man may eat of the flesh of beasts, so may gods eat of the flesh of man. The Holy Therns are the gods of Barsoom."

I was disgusted and I imagine that I showed it.

"You are an unbeliever now," she continued gently, "but should we be fortunate enough to escape the clutches of the black pirates and come again to the court of Matai Shang I think that we shall find an argument to convince you of the error of your ways. And--," she hesitated, "perhaps we shall find a way to keep you as--as--one of us."

Again her eyes dropped to the floor, and a faint colour suffused her cheek. I could not understand her meaning; nor did I for a long time. Dejah Thoris was wont to say that in some things I was a veritable simpleton, and I guess that she was right.

"I fear that I would ill requite your father's hospitality," I answered, "since the first thing that I should do were I a thern would be to set an armed guard at the mouth of the River Iss to escort the poor deluded voyagers back to the outer world. Also should I devote my life to the extermination of the hideous plant men and their horrible companions, the great white apes."

She looked at me really horror struck.

"No, no," she cried, "you must not say such terribly sacrilegious things--you must not even think them. Should they ever guess that you entertained such frightful thoughts, should we chance to regain the temples of the therns, they would mete out a frightful death to you. Not even my--my--" Again she flushed, and started over. "Not even I could save you."

I said no more. Evidently it was useless. She was even more steeped in superstition than the Martians of the outer world. They only worshipped a beautiful hope for a life of love and peace and happiness in the hereafter. The therns worshipped the hideous plant men and the apes, or at least they reverenced them as the abodes of the departed spirits of their own dead.

At this point the door of our prison opened to admit Xodar.

He smiled pleasantly at me, and when he smiled his expression was kindly--anything but cruel or vindictive.

"Since you cannot escape under any circumstances," he said, "I cannot see the necessity for keeping you confined below. I will cut your bonds and you may come on deck. You will witness something very interesting, and as you never shall return to the outer world it will do no harm to permit you to see it. You will see what no other than the First Born and their slaves know the existence of--the subterranean entrance to the Holy Land, to the real heaven of Barsoom.

"It will be an excellent lesson for this daughter of the therns," he added, "for she shall see the Temple of Issus, and Issus, perchance, shall embrace her."

Phaidor's head went high.

"What blasphemy is this, dog of a pirate?" she cried. "Issus would wipe out your entire breed an' you ever came within sight of her temple."

"You have much to learn, thern," replied Xodar, with an ugly smile, "nor do I envy you the manner in which you will learn it."

As we came on deck I saw to my surprise that the vessel was passing over a great field of snow and ice. As far as the eye could reach in any direction naught else was visible.

There could be but one solution to the mystery. We were above the south polar ice cap. Only at the poles of Mars is there ice or snow upon the planet. No sign of life appeared below us. Evidently we were too far south even for the great fur-bearing animals which the Martians so delight in hunting.

Xodar was at my side as I stood looking out over the ship's rail.

"What course?" I asked him.

"A little west of south," he replied. "You will see the Otz Valley directly. We shall skirt it for a few hundred miles."

"The Otz Valley!" I exclaimed; "but, man, is not there where lie the domains of the therns from which I but just escaped?"

"Yes," answered Xodar. "You crossed this ice field last night in the long chase that you led us. The Otz Valley lies in a mighty depression at the south pole. It is sunk thousands of feet below the level of the surrounding country, like a great round bowl. A hundred miles from its northern boundary rise the Otz Mountains which circle the inner Valley of Dor, in the exact centre of which lies the Lost Sea of Korus. On the shore of this sea stands the Golden Temple of Issus in the Land of the First Born. It is there that we are bound."

As I looked I commenced to realize why it was that in all the ages only one had escaped from the Valley Dor. My only wonder was that even the one had been successful. To cross this frozen, wind-swept waste of bleak ice alone and on foot would be impossible.

"Only by air boat could the journey be made," I finished aloud.

"It was thus that one did escape the therns in bygone times; but none has ever escaped the First Born," said Xodar, with a touch of pride in his voice.

We had now reached the southernmost extremity of the great ice barrier. It ended abruptly in a sheer wall thousands of feet high at the base of which stretched a level valley, broken here and there by low rolling hills and little clumps of forest, and with tiny rivers formed by the melting of the ice barrier at its base.

Once we passed far above what seemed to be a deep canyon-like rift stretching from the ice wall on the north across the valley as far as the eye could reach. "That is the bed of the River Iss," said Xodar. "It runs far beneath the ice field, and below the level of the Valley Otz, but its canyon is open here."

Presently I descried what I took to be a village, and pointing it out to Xodar asked him what it might be.

"It is a village of lost souls," he answered, laughing. "This strip between the ice barrier and the mountains is considered neutral ground. Some turn off from their voluntary pilgrimage down the Iss, and, scaling the awful walls of its canyon below us, stop in the valley. Also a slave now and then escapes from the therns and makes his way hither.

"They do not attempt to recapture such, since there is no escape from this outer valley, and as a matter of fact they fear the patrolling cruisers of the First Born too much to venture from their own domains.

"The poor creatures of this outer valley are not molested by us since they have nothing that we desire, nor are they numerically strong enough to give us an interesting fight--so we too leave them alone.

"There are several villages of them, but they have increased in numbers but little in many years since they are always warring among themselves."

Now we swung a little north of west, leaving the valley of lost souls, and shortly I discerned over our starboard bow what appeared to be a black mountain rising from the desolate waste of ice. It was not high and seemed to have a flat top.

Xodar had left us to attend to some duty on the vessel, and Phaidor and I stood alone beside the rail. The girl had not once spoken since we had been brought to the deck.

"Is what he has been telling me true?" I asked her.

"In part, yes," she answered. "That about the outer valley is true, but what he says of the location of the Temple of Issus in the centre of his country is false. If it is not false--" she hesitated. "Oh it cannot be true, it cannot be true. For if it were true then for countless ages have my people gone to torture and ignominious death at the hands of their cruel enemies, instead of to the beautiful Life Eternal that we have been taught to believe Issus holds for us."

"As the lesser Barsoomians of the outer world have been lured by you to the terrible Valley Dor, so may it be that the therns themselves have been lured by the First Born to an equally horrid fate," I suggested. "It would be a stern and awful retribution, Phaidor; but a just one."

"I cannot believe it," she said.

"We shall see," I answered, and then we fell silent again for we were rapidly approaching the black mountains, which in some indefinable way seemed linked with the answer to our problem.

As we neared the dark, truncated cone the vessel's speed was diminished until we barely moved. Then we topped the crest of the mountain and below us I saw yawning the mouth of a huge circular well, the bottom of which was lost in inky blackness.

The diameter of this enormous pit was fully a thousand feet. The walls were smooth and appeared to be composed of a black, basaltic rock.

For a moment the vessel hovered motionless directly above the centre of the gaping void, then slowly she began to settle into the black chasm. Lower and lower she sank until as darkness enveloped us her lights were thrown on and in the dim halo of her own radiance the monster battleship dropped on and on down into what seemed to me must be the very bowels of Barsoom.

For quite half an hour we descended and then the shaft terminated abruptly in the dome of a mighty subterranean world. Below us rose and fell the billows of a buried sea. A phosphorescent radiance illuminated the scene. Thousands of ships dotted the bosom of the ocean. Little islands rose here and there to support the strange and colourless vegetation of this strange world.

Slowly and with majestic grace the battleship dropped until she rested on the water. Her great propellers had been drawn and housed during our descent of the shaft and in their place had been run out the smaller but more powerful water propellers. As these commenced to revolve the ship took up its journey once more, riding the new element as buoyantly and as safely as she had the air.

Phaidor and I were dumbfounded. Neither had either heard or dreamed that such a world existed beneath the surface of Barsoom.

Nearly all the vessels we saw were war craft. There were a few lighters and barges, but none of the great merchantmen such as ply the upper air between the cities of the outer world.

"Here is the harbour of the navy of the First Born," said a voice behind us, and turning we saw Xodar watching us with an amused smile on his lips.

"This sea," he continued, "is larger than Korus. It receives the waters of the lesser sea above it. To keep it from filling above a certain level we have four great pumping stations that force the oversupply back into the reservoirs far north from which the red men draw the water which irrigates their farm lands."

A new light burst on me with this explanation. The red men had always considered it a miracle that caused great columns of water to spurt from the solid rock of their reservoir sides to increase the supply of the precious liquid which is so scarce in the outer world of Mars.

Never had their learned men been able to fathom the secret of the source of this enormous volume of water. As ages passed they had simply come to accept it as a matter of course and ceased to question its origin.

We passed several islands on which were strangely shaped circular buildings, apparently roofless, and pierced midway between the ground and their tops with small, heavily barred windows. They bore the earmarks of prisons, which were further accentuated by the armed guards who squatted on low benches without, or patrolled the short beach lines.

Few of these islets contained over an acre of ground, but presently we sighted a much larger one directly ahead. This proved to be our destination, and the great ship was soon made fast against the steep shore.

Xodar signalled us to follow him and with a half-dozen officers and men we left the battleship and approached a large oval structure a couple of hundred yards from the shore.

"You shall soon see Issus," said Xodar to Phaidor. "The few prisoners we take are presented to her. Occasionally she selects slaves from among them to replenish the ranks of her handmaidens. None serves Issus above a single year," and there was a grim smile on the black's lips that lent a cruel and sinister meaning to his simple statement.

Phaidor, though loath to believe that Issus was allied to such as these, had commenced to entertain doubts and fears. She clung very closely to me, no longer the proud daughter of the Master of Life and Death upon Barsoom, but a young and frightened girl in the power of relentless enemies.

The building which we now entered was entirely roofless. In its centre was a long tank of water, set below the level of the floor like the swimming pool of a natatorium. Near one side of the pool floated an odd-looking black object. Whether it were some strange monster of these buried waters, or a queer raft, I could not at once perceive.

We were soon to know, however, for as we reached the edge of the pool directly above the thing, Xodar cried out a few words in a strange tongue. Immediately a hatch cover was raised from the surface of the object, and a black seaman sprang from the bowels of the strange craft.

Xodar addressed the seaman.

"Transmit to your officer," he said, "the commands of Dator Xodar. Say to him that Dator Xodar, with officers and men, escorting two prisoners, would be transported to the gardens of Issus beside the Golden Temple."

"Blessed be the shell of thy first ancestor, most noble Dator," replied the man. "It shall be done even as thou sayest," and raising both hands, palms backward, above his head after the manner of salute which is common to all races of Barsoom, he disappeared once more into the entrails of his ship.

A moment later an officer resplendent in the gorgeous trappings of his rank appeared on deck and welcomed Xodar to the vessel, and in the latter's wake we filed aboard and below.

The cabin in which we found ourselves extended entirely across the ship, having port-holes on either side below the water line. No sooner were all below than a number of commands were given, in accordance with which the hatch was closed and secured, and the vessel commenced to vibrate to the rhythmic purr of its machinery.

"Where can we be going in such a tiny pool of water?" asked Phaidor.

"Not up," I replied, "for I noticed particularly that while the building is roofless it is covered with a strong metal grating."

"Then where?" she asked again.

"From the appearance of the craft I judge we are going down," I replied.

Phaidor shuddered. For such long ages have the waters of Barsoom's seas been a thing of tradition only that even this daughter of the therns, born as she had been within sight of Mars' only remaining sea, had the same terror of deep water as is a common attribute of all Martians.

Presently the sensation of sinking became very apparent. We were going down swiftly. Now we could hear the water rushing past the port-holes, and in the dim light that filtered through them to the water beyond the swirling eddies were plainly visible.

Phaidor grasped my arm.

"Save me!" she whispered. "Save me and your every wish shall be granted. Anything within the power of the Holy Therns to give will be yours. Phaidor--" she stumbled a little here, and then in a very low voice, "Phaidor already is yours."

I felt very sorry for the poor child, and placed my hand over hers where it rested on my arm. I presume my motive was misunderstood, for with a swift glance about the apartment to assure herself that we were alone, she threw both her arms about my neck and dragged my face down to hers.