I raised the bar and shot it to the right just as the foremost of the guardsmen threw himself against the opposite side of the massive panels.

The barrier held-I had been in time, but by the fraction of a second only.

Now I turned my attention to the prisoners. To Tardos Mors I went first, asking where the keys might be which would unfasten their fetters.

"The officer of the guard has them," replied the Jeddak of Helium, "and he is among those without who seek entrance. You will have to force them."

Most of the prisoners were already hacking at their bonds with the swords in their hands. The yellow men were battering at the door with javelins and axes.

I turned my attention to the chains that held Tardos Mors. Again and again I cut deep into the metal with my sharp blade, but ever faster and faster fell the torrent of blows upon the portal.

At last a link parted beneath my efforts, and a moment later Tardos Mors was free, though a few inches of trailing chain still dangled from his ankle.

A splinter of wood falling inward from the door announced the headway that our enemies were making toward us.

The mighty panels trembled and bent beneath the furious onslaught of the enraged yellow men.

What with the battering upon the door and the hacking of the red men at their chains the din within the armory was appalling. No sooner was Tardos Mors free than he turned his attention to another of the prisoners, while I set to work to liberate Mors Kajak.

We must work fast if we would have all those fetters cut before the door gave way. Now a panel crashed inward upon the floor, and Mors Kajak sprang to the opening to defend the way until we should have time to release the others.

With javelins snatched from the wall he wrought havoc among the foremost of the Okarians while we battled with the insensate metal that stood between our fellows and freedom.

At length all but one of the prisoners were freed, and then the door fell with a mighty crash before a hastily improvised battering-ram, and the yellow horde was upon us.

"To the upper chambers!" shouted the red man who was still fettered to the floor. "To the upper chambers! There you may defend the tower against all Kadabra. Do not delay because of me, who could pray for no better death than in the service of Tardos Mors and the Prince of Helium."

But I would have sacrificed the life of every man of us rather than desert a single red man, much less the lion-hearted hero who begged us to leave him.

"Cut his chains," I cried to two of the red men, "while the balance of us hold off the foe."

There were ten of us now to do battle with the Okarian guard, and I warrant that that ancient watchtower never looked down upon a more hotly contested battle than took place that day within its own grim walls.

The first inrushing wave of yellow warriors recoiled from the slashing blades of ten of Helium's veteran fighting men. A dozen Okarian corpses blocked the doorway, but over the gruesome barrier a score more of their fellows dashed, shouting their hoarse and hideous war-cry.

Upon the bloody mound we met them, hand to hand, stabbing where the quarters were too close to cut, thrusting when we could push a foeman to arm's length; and mingled with the wild cry of the Okarian there rose and fell the glorious words: "For Helium! For Helium!" that for countless ages have spurred on the bravest of the brave to those deeds of valor that have sent the fame of Helium's heroes broadcast throughout the length and breadth of a world.

Now were the fetters struck from the last of the red men, and thirteen strong we met each new charge of the soldiers of Salensus Oll. Scarce one of us but bled from a score of wounds, yet none had fallen.

From without we saw hundreds of guardsmen pouring into the courtyard, and along the lower corridor from which I had found my way to the armory we could hear the clank of metal and the shouting of men.

In a moment we should be attacked from two sides, and with all our prowess we could not hope to withstand the unequal odds which would thus divide our attention and our small numbers.

"To the upper chambers!" cried Tardos Mors, and a moment later we fell back toward the runway that led to the floors above.

Here another bloody battle was waged with the force of yellow men who charged into the armory as we fell back from the doorway. Here we lost our first man, a noble fellow whom we could ill spare; but at length all had backed into the runway except myself, who remained to hold back the Okarians until the others were safe above.

In the mouth of the narrow spiral but a single warrior could attack me at a time, so that I had little difficulty in holding them all back for the brief moment that was necessary. Then, backing slowly before them, I commenced the ascent of the spiral.

All the long way to the tower's top the guardsmen pressed me closely. When one went down before my sword another scrambled over the dead man to take his place; and thus, taking an awful toll with each few feet gained, I came to the spacious glass-walled watchtower of Kadabra.

Here my companions clustered ready to take my place, and for a moment's respite I stepped to one side while they held the enemy off.

From the lofty perch a view could be had for miles in every direction. Toward the south stretched the rugged, ice-clad waste to the edge of the mighty barrier. Toward the east and west, and dimly toward the north I descried other Okarian cities, while in the immediate foreground, just beyond the walls of Kadabra, the grim guardian shaft reared its somber head.

Then I cast my eyes down into the streets of Kadabra, from which a sudden tumult had arisen, and there I saw a battle raging, and beyond the city's walls I saw armed men marching in great columns toward a near-by gate.

Eagerly I pressed forward against the glass wall of the observatory, scarce daring to credit the testimony of my own eyes. But at last I could doubt no longer, and with a shout of joy that rose strangely in the midst of the cursing and groaning of the battling men at the entrance to the chamber, I called to Tardos Mors.

As he joined me I pointed down into the streets of Kadabra and to the advancing columns beyond, above which floated bravely in the arctic air the flags and banners of Helium.

An instant later every red man in the lofty chamber had seen the inspiring sight, and such a shout of thanksgiving arose as I warrant never before echoed through that age-old pile of stone.

But still we must fight on, for though our troops had entered Kadabra, the city was yet far from capitulation, nor had the palace been even assaulted. Turn and turn about we held the top of the runway while the others feasted their eyes upon the sight of our valiant countrymen battling far beneath us.

Now they have rushed the palace gate! Great battering-rams are dashed against its formidable surface. Now they are repulsed by a deadly shower of javelins from the wall's top!

Once again they charge, but a sortie by a large force of Okarians from an intersecting avenue crumples the head of the column, and the men of Helium go down, fighting, beneath an overwhelming force.

The palace gate flies open and a force of the jeddak's own guard, picked men from the flower of the Okarian army, sallies forth to shatter the broken regiments. For a moment it looks as though nothing could avert defeat, and then I see a noble figure upon a mighty thoat-not the tiny thoat of the red man, but one of his huge cousins of the dead sea bottoms.

The warrior hews his way to the front, and behind him rally the disorganized soldiers of Helium. As he raises his head aloft to fling a challenge at the men upon the palace walls I see his face, and my heart swells in pride and happiness as the red warriors leap to the side of their leader and win back the ground that they had but just lost-the face of him upon the mighty thoat is the face of my son-Carthoris of Helium.

At his side fights a huge Martian war-hound, nor did I need a second look to know that it was Woola-my faithful Woola who had thus well performed his arduous task and brought the succoring legions in the nick of time.

"In the nick of time?"

Who yet might say that they were not too late to save, but surely they could avenge! And such retribution as that unconquered army would deal out to the hateful Okarians! I sighed to think that I might not be alive to witness it.

Again I turned to the windows. The red men had not yet forced the outer palace wall, but they were fighting nobly against the best that Okar afforded-valiant warriors who contested every inch of the way.

Now my attention was caught by a new element without the city wall-a great body of mounted warriors looming large above the red men. They were the huge green allies of Helium-the savage hordes from the dead sea bottoms of the far south.

In grim and terrible silence they sped on toward the gate, the padded hoofs of their frightful mounts giving forth no sound. Into the doomed city they charged, and as they wheeled across the wide plaza before the palace of the Jeddak of Jeddaks I saw, riding at their head, the mighty figure of their mighty leader-Tars Tarkas, Jeddak of Thark.

My wish, then, was to be gratified, for I was to see my old friend battling once again, and though not shoulder to shoulder with him, I, too, would be fighting in the same cause here in the high tower of Okar.

Nor did it seem that our foes would ever cease their stubborn attacks, for still they came, though the way to our chamber was often clogged with the bodies of their dead. At times they would pause long enough to drag back the impeding corpses, and then fresh warriors would forge upward to taste the cup of death.

I had been taking my turn with the others in defending the approach to our lofty retreat when Mors Kajak, who had been watching the battle in the street below, called aloud in sudden excitement. There was a note of apprehension in his voice that brought me to his side the instant that I could turn my place over to another, and as I reached him he pointed far out across the waste of snow and ice toward the southern horizon.

"Alas!" he cried, "that I should be forced to witness cruel fate betray them without power to warn or aid; but they be past either now."

As I looked in the direction he indicated I saw the cause of his perturbation. A mighty fleet of fliers was approaching majestically toward Kadabra from the direction of the ice-barrier. On and on they came with ever increasing velocity.

"The grim shaft that they call the Guardian of the North is beckoning to them," said Mors Kajak sadly, "just as it beckoned to Tardos Mors and his great fleet; see where they lie, crumpled and broken, a grim and terrible monument to the mighty force of destruction which naught can resist."

I, too, saw; but something else I saw that Mors Kajak did not; in my mind's eye I saw a buried chamber whose walls were lined with strange instruments and devices.

In the center of the chamber was a long table, and before it sat a little, pop-eyed old man counting his money; but, plainest of all, I saw upon the wall a great switch with a small magnet inlaid within the surface of its black handle.

Then I glanced out at the fast-approaching fleet. In five minutes that mighty armada of the skies would be bent and worthless scrap, lying at the base of the shaft beyond the city's wall, and yellow hordes would be loosed from another gate to rush out upon the few survivors stumbling blindly down through the mass of wreckage; then the apts would come. I shuddered at the thought, for I could vividly picture the whole horrible scene.

Quick have I always been to decide and act.