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.