The morning of the second day of her incarceration in the east tower of the palace of Astok, Prince of Dusar, found Thuvia of Ptarth waiting in dull apathy the coming of the assassin.

She had exhausted every possibility of escape, going over and over again the door and the windows, the floor and the walls.

The solid ersite slabs she could not even scratch; the tough Barsoomian glass of the windows would have shattered to nothing less than a heavy sledge in the hands of a strong man. The door and the lock were impregnable. There was no escape. And they had stripped her of her weapons so that she could not even anticipate the hour of her doom, thus robbing them of the satisfaction of witnessing her last moments.

When would they come? Would Astok do the deed with his own hands? She doubted that he had the courage for it. At heart he was a coward — she had known it since first she had heard him brag as, a visitor at the court of her father, he had sought to impress her with his valour.

She could not help but compare him with another. And with whom would an affianced bride compare an unsuccessful suitor? With her betrothed? And did Thuvia of Ptarth now measure Astok of Dusar by the standards of Kulan Tith, Jeddak of Kaol?

She was about to die; her thoughts were her own to do with as she pleased; yet furthest from them was Kulan Tith. Instead the figure of the tall and comely Heliumite filled her mind, crowding therefrom all other images.

She dreamed of his noble face, the quiet dignity of his bearing, the smile that lit his eyes as he conversed with his friends, and the smile that touched his lips as he fought with his enemies — the fighting smile of his Virginian sire.

And Thuvia of Ptarth, true daughter of Barsoom, found her breath quickening and heart leaping to the memory of this other smile — the smile that she would never see again. With a little half-sob the girl sank to the pile of silks and furs that were tumbled in confusion beneath the east windows, burying her face in her arms.

In the corridor outside her prison-room two men had paused in heated argument.

"I tell you again, Astok," one was saying, "that I shall not do this thing unless you be present in the room."

There was little of the respect due royalty in the tone of the speaker's voice. The other, noting it, flushed.

"Do not impose too far upon my friendship for you, Vas Kor," he snapped. "There is a limit to my patience."

"There is no question of royal prerogative here," returned Vas Kor. "You ask me to become an assassin in your stead, and against your jeddak's strict injunctions. You are in no position, Astok, to dictate to me; but rather should you be glad to accede to my reasonable request that you be present, thus sharing the guilt with me. Why should I bear it all?"

The younger man scowled, but he advanced toward the locked door, and as it swung in upon its hinges, he entered the room beyond at the side of Vas Kor.

Across the chamber the girl, hearing them enter, rose to her feet and faced them. Under the soft copper of her skin she blanched just a trifle; but her eyes were brave and level, and the haughty tilt of her firm little chin was eloquent of loathing and contempt.

"You still prefer death?" asked Astok.

"To YOU, yes," replied the girl coldly.

The Prince of Dusar turned to Vas Kor and nodded. The noble drew his short-sword and crossed the room toward Thuvia.

"Kneel!" he commanded.

"I prefer to die standing," she replied.

"As you will," said Vas Kor, feeling the point of his blade with his left thumb. "In the name of Nutus, Jeddak of Dusar!" he cried, and ran quickly toward her.

"In the name of Carthoris, Prince of Helium!" came in low tones from the doorway.

Vas Kor turned to see the panthan he had recruited at his son's house leaping across the floor toward him. The fellow brushed past Astok with an: "After him, you — calot!"

Vas Kor wheeled to meet the charging man.

"What means this treason?" he cried.

Astok, with bared sword, leaped to Vas Kor's assistance. The panthan's sword clashed against that of the noble, and in the first encounter Vas Kor knew that he faced a master swordsman.

Before he half realized the stranger's purpose he found the man between himself and Thuvia of Ptarth, at bay facing the two swords of the Dusarians. But he fought not like a man at bay. Ever was he the aggressor, and though always he kept his flashing blade between the girl and her enemies, yet he managed to force them hither and thither about the room, calling to the girl to follow close behind him.

Until it was too late neither Vas Kor nor Astok dreamed of that which lay in the panthan's mind; but at last as the fellow stood with his back toward the door, both understood — they were penned in their own prison, and now the intruder could slay them at his will, for Thuvia of Ptarth was bolting the door at the man's direction, first taking the key from the opposite side, where Astok had left it when they had entered.

Astok, as was his way, finding that the enemy did not fall immediately before their swords, was leaving the brunt of the fighting to Vas Kor, and now as his eyes appraised the panthan carefully they presently went wider and wider, for slowly he had come to recognize the features of the Prince of Helium.

The Heliumite was pressing close upon Vas Kor. The noble was bleeding from a dozen wounds. Astok saw that he could not for long withstand the cunning craft of that terrible sword hand.

"Courage, Vas Kor!" he whispered in the other's ear. "I have a plan. Hold him but a moment longer and all will be well," but the balance of the sentence, "with Astok, Prince of Dusar," he did not voice aloud.

Vas Kor, dreaming no treachery, nodded his head, and for a moment succeeded in holding Carthoris at bay. Then the Heliumite and the girl saw the Dusarian prince run swiftly to the opposite side of the chamber, touch something in the wall that sent a great panel swinging inward, and disappear into the black vault beyond.

It was done so quickly that by no possibility could they have intercepted him. Carthoris, fearful lest Vas Kor might similarly elude him, or Astok return immediately with reinforcements, sprang viciously in upon his antagonist, and a moment later the headless body of the Dusarian noble rolled upon the ersite floor.

"Come!" cried Carthoris. "There is no time to be lost. Astok will be back in a moment with enough warriors to overpower me."

But Astok had no such plan in mind, for such a move would have meant the spreading of the fact among the palace gossips that the Ptarthian princess was a prisoner in the east tower. Quickly would the word have come to his father, and no amount of falsifying could have explained away the facts that the jeddak's investigation would have brought to light.

Instead Astok was racing madly through a long corridor to reach the door of the tower-room before Carthoris and Thuvia left the apartment. He had seen the girl remove the key and place it in her pocket-pouch, and he knew that a dagger point driven into the keyhole from the opposite side would imprison them in the secret chamber till eight dead worlds circled a cold, dead sun.

As fast as he could run Astok entered the main corridor that led to the tower chamber. Would he reach the door in time? What if the Heliumite should have already emerged and he should run upon him in the passageway? Astok felt a cold chill run up his spine. He had no stomach to face that uncanny blade.

He was almost at the door. Around the next turn of the corridor it stood. No, they had not left the apartment. Evidently Vas Kor was still holding the Heliumite!

Astok could scarce repress a grin at the clever manner in which he had outwitted the noble and disposed of him at the same time. And then he rounded the turn and came face to face with an auburn-haired, white giant.

The fellow did not wait to ask the reason for his coming; instead he leaped upon him with a long-sword, so that Astok had to parry a dozen vicious cuts before he could disengage himself and flee back down the runway.

A moment later Carthoris and Thuvia entered the corridor from the secret chamber.

"Well, Kar Komak?" asked the Heliumite.

"It is fortunate that you left me here, red man," said the bowman. "I but just now intercepted one who seemed over-anxious to reach this door — it was he whom they call Astok, Prince of Dusar."

Carthoris smiled.

"Where is he now?" he asked.

"He escaped my blade, and ran down this corridor," replied Kar Komak.

"We must lose no time, then!" exclaimed Carthoris. "He will have the guard upon us yet!"

Together the three hastened along the winding passages through which Carthoris and Kar Komak had tracked the Dusarians by the marks of the latter's sandals in the thin dust that overspread the floors of these seldom-used passage-ways.

They had come to the chamber at the entrances to the lifts before they met with opposition. Here they found a handful of guardsmen, and an officer, who, seeing that they were strangers, questioned their presence in the palace of Astok.

Once more Carthoris and Kar Komak had recourse to their blades, and before they had won their way to one of the lifts the noise of the conflict must have aroused the entire palace, for they heard men shouting, and as they passed the many levels on their quick passage to the landing-stage they saw armed men running hither and thither in search of the cause of the commotion.

Beside the stage lay the Thuria, with three warriors on guard. Again the Heliumite and the Lotharian fought shoulder to shoulder, but the battle was soon over, for the Prince of Helium alone would have been a match for any three that Dusar could produce.

Scarce had the Thuria risen from the ways ere a hundred or more fighting men leaped to view upon the landing-stage. At their head was Astok of Dusar, and as he saw the two he had thought so safely in his power slipping from his grasp, he danced with rage and chagrin, shaking his fists and hurling abuse and vile insults at them.

With her bow inclined upward at a dizzy angle, the Thuria shot meteor-like into the sky. From a dozen points swift patrol boats darted after her, for the scene upon the landing-stage above the palace of the Prince of Dusar had not gone unnoticed.

A dozen times shots grazed the Thuria's side, and as Carthoris could not leave the control levers, Thuvia of Ptarth turned the muzzles of the craft's rapid-fire guns upon the enemy as she clung to the steep and slippery surface of the deck.

It was a noble race and a noble fight. One against a score now, for other Dusarian craft had joined in the pursuit; but Astok, Prince of Dusar, had built well when he built the Thuria. None in the navy of his sire possessed a swifter flier; no other craft so well armoured or so well armed.

One by one the pursuers were distanced, and as the last of them fell out of range behind, Carthoris dropped the Thuria's nose to a horizontal plane, as with lever drawn to the last notch, she tore through the thin air of dying Mars toward the east and Ptarth.

Thirteen and a half thousand haads away lay Ptarth — a stiff thirty-hour journey for the swiftest of fliers, and between Dusar and Ptarth might lie half the navy of Dusar, for in this direction was the reported seat of the great naval battle that even now might be in progress.

Could Carthoris have known precisely where the great fleets of the contending nations lay, he would have hastened to them without delay, for in the return of Thuvia to her sire lay the greatest hope of peace.

Half the distance they covered without sighting a single warship, and then Kar Komak called Carthoris's attention to a distant craft that rested upon the ochre vegetation of the great dead sea-bottom, above which the Thuria was speeding.

About the vessel many figures could be seen swarming. With the aid of powerful glasses, the Heliumite saw that they were green warriors, and that they were repeatedly charging down upon the crew of the stranded airship. The nationality of the latter he could not make out at so great a distance.

It was not necessary to change the course of the Thuria to permit of passing directly above the scene of battle, but Carthoris dropped his craft a few hundred feet that he might have a better and closer view.

If the ship was of a friendly power, he could do no less than stop and direct his guns upon her enemies, though with the precious freight he carried he scarcely felt justified in landing, for he could offer but two swords in reinforcement — scarce enough to warrant jeopardizing the safety of the Princess of Ptarth.

As they came close above the stricken ship, they could see that it would be but a question of minutes before the green horde would swarm across the armoured bulwarks to glut the ferocity of their bloodlust upon the defenders.

"It would be futile to descend," said Carthoris to Thuvia. "The craft may even be of Dusar — she shows no insignia. All that we may do is fire upon the hordesmen"; and as he spoke he stepped to one of the guns and deflected its muzzle toward the green warriors at the ship's side.

At the first shot from the Thuria those upon the vessel below evidently discovered her for the first time. Immediately a device fluttered from the bow of the warship on the ground. Thuvia of Ptarth caught her breath quickly, glancing at Carthoris.

The device was that of Kulan Tith, Jeddak of Kaol — the man to whom the Princess of Ptarth was betrothed!

How easy for the Heliumite to pass on, leaving his rival to the fate that could not for long be averted! No man could accuse him of cowardice or treachery, for Kulan Tith was in arms against Helium, and, further, upon the Thuria were not enough swords to delay even temporarily the outcome that already was a foregone conclusion in the minds of the watchers.

What would Carthoris, Prince of Helium, do?

Scarce had the device broken to the faint breeze ere the bow of the Thuria dropped at a sharp angle toward the ground.

"Can you navigate her?" asked Carthoris of Thuvia.

The girl nodded.

"I am going to try to take the survivors aboard," he continued. "It will need both Kar Komak and myself to man the guns while the Kaolians take to the boarding tackle. Keep her bow depressed against the rifle fire. She can bear it better in her forward armour, and at the same time the propellers will be protected."

He hurried to the cabin as Thuvia took the control. A moment later the boarding tackle dropped from the keel of the Thuria, and from a dozen points along either side stout, knotted leathern lines trailed downward. At the same time a signal broke from her bow:

"Prepare to board us."

A shout arose from the deck of the Kaolian warship. Carthoris, who by this time had returned from the cabin, smiled sadly. He was about to snatch from the jaws of death the man who stood between himself and the woman he loved.

"Take the port bow gun, Kar Komak," he called to the bowman, and himself stepped to the gun upon the starboard bow.

It was a forlorn hope at best. At any moment the repulsive ray tanks might be pierced. The men upon the Kaolian ship were battling with renewed hope. In the bow stood Kulan Tith, a brave figure fighting beside his brave warriors, beating back the ferocious green men.

The Thuria came low above the other craft. The Kaolians were forming under their officers in readiness to board, and then a sudden fierce fusillade from the rifles of the green warriors vomited their hail of death and destruction into the side of the brave flier.

Like a wounded bird she dived suddenly Marsward careening drunkenly. Thuvia turned the bow upward in an effort to avert the imminent tragedy, but she succeeded only in lessening the shock of the flier's impact as she struck the ground beside the Kaolian ship.

When the green men saw only two warriors and a woman upon the deck of the Thuria, a savage shout of triumph arose from their ranks, while an answering groan broke from the lips of the Kaolians.

The former now turned their attention upon the new arrival, for they saw her defenders could soon be overcome and that from her deck they could command the deck of the better-manned ship.

As they charged a shout of warning came from Kulan Tith, upon the bridge of his own ship, and with it an appreciation of the valour of the act that had put the smaller vessel in these sore straits.

"Who is it," he cried, "that offers his life in the service of Kulan Tith? Never was wrought a nobler deed of self-sacrifice upon Barsoom!"

The green horde was scrambling over the Thuria's side as there broke from the bow the device of Carthoris, Prince of Helium, in reply to the query of the jeddak of Kaol. None upon the smaller flier had opportunity to note the effect of this announcement upon the Kaolians, for their attention was claimed slowly now by that which was transpiring upon their own deck.

Kar Komak stood behind the gun he had been operating, staring with wide eyes at the onrushing hideous green warriors. Carthoris, seeing him thus, felt a pang of regret that, after all, this man that he had thought so valorous should prove, in the hour of need, as spineless as Jav or Tario.

"Kar Komak — the man!" he shouted. "Grip yourself! Remember the days of the glory of the seafarers of Lothar. Fight! Fight, man! Fight as never man fought before. All that remains to us is to die fighting."

Kar Komak turned toward the Heliumite, a grim smile upon his lips.

"Why should we fight," he asked. "Against such fearful odds? There is another way — a better way. Look!" He pointed toward the companion-way that led below deck.

The green men, a handful of them, had already reached the Thuria's deck, as Carthoris glanced in the direction the Lotharian had indicated. The sight that met his eyes set his heart to thumping in joy and relief — Thuvia of Ptarth might yet be saved? For from below there poured a stream of giant bowmen, grim and terrible. Not the bowmen of Tario or Jav, but the bowmen of an odwar of bowmen — savage fighting men, eager for the fray.

The green warriors paused in momentary surprise and consternation, but only for a moment. Then with horrid war-cries they leaped forward to meet these strange, new foemen.

A volley of arrows stopped them in their tracks. In a moment the only green warriors upon the deck of the Thuria were dead warriors, and the bowmen of Kar Komak were leaping over the vessel's sides to charge the hordesmen upon the ground.

Utan after utan tumbled from the bowels of the Thuria to launch themselves upon the unfortunate green men. Kulan Tith and his Kaolians stood wide-eyed and speechless with amazement as they saw thousands of these strange, fierce warriors emerge from the companion-way of the small craft that could not comfortably have accommodated more than fifty.

At last the green men could withstand the onslaught of overwhelming numbers no longer. Slowly, at first, they fell back across the ochre plain. The bowmen pursued them. Kar Komak, standing upon the deck of the Thuria, trembled with excitement.

At the top of his lungs he voiced the savage war-cry of his forgotten day. He roared encouragement and commands at his battling utans, and then, as they charged further and further from the Thuria, he could no longer withstand the lure of battle.

Leaping over the ship's side to the ground, he joined the last of his bowmen as they raced off over the dead sea-bottom in pursuit of the fleeing green horde.

Beyond a low promontory of what once had been an island the green men were disappearing toward the west. Close upon their heels raced the fleet bowmen of a bygone day, and forging steadily ahead among them Carthoris and Thuvia could see the mighty figure of Kar Komak, brandishing aloft the Torquasian short-sword with which he was armed, as he urged his creatures after the retreating enemy.

As the last of them disappeared behind the promontory, Carthoris turned toward Thuvia of Ptarth.

"They have taught me a lesson, these vanishing bowmen of Lothar," he said. "When they have served their purpose they remain not to embarrass their masters by their presence. Kulan Tith and his warriors are here to protect you. My acts have constituted the proof of my honesty of purpose. Good-bye," and he knelt at her feet, raising a bit of her harness to his lips.

The girl reached out a hand and laid it upon the thick black hair of the head bent before her. Softly she asked:

"Where are you going, Carthoris?"

"With Kar Komak, the bowman," he replied. "There will be fighting and forgetfulness."

The girl put her hands before her eyes, as though to shut out some mighty temptation from her sight.

"May my ancestors have mercy upon me," she cried, "if I say the thing I have no right to say; but I cannot see you cast your life away, Carthoris, Prince of Helium! Stay, my chieftain. Stay — I love you!"

A cough behind them brought both about, and there they saw standing, not two paces from them Kulan Tith, Jeddak of Kaol.

For a long moment none spoke. Then Kulan Tith cleared his throat.

"I could not help hearing all that passed," he said. "I am no fool, to be blind to the love that lies between you. Nor am I blind to the lofty honour that has caused you, Carthoris, to risk your life and hers to save mine, though you thought that that very act would rob you of the chance to keep her for your own.

"Nor can I fail to appreciate the virtue that has kept your lips sealed against words of love for this Heliumite, Thuvia, for I know that I have but just heard the first declaration of your passion for him. I do not condemn you. Rather should I have condemned you had you entered a loveless marriage with me.

"Take back your liberty, Thuvia of Ptarth," he cried, "and bestow it where your heart already lies enchained, and when the golden collars are clasped about your necks you will see that Kulan Tith's is the first sword to be raised in declaration of eternal friendship for the new Princess of Helium and her royal mate!"