One of the guardsmen, a giant of a fellow across whose right cheek there ran a thin scar from temple to mouth, approached his companion. His gaze was directed beyond and above his comrade. When he had come quite close he spoke.

«What strange craft is that?» he asked.

The other turned about quickly to gaze heavenward. Scarce was his back turned toward the giant than the short-sword of the latter was plunged beneath his left shoulder blade, straight through his heart.

Voiceless, the soldier sank in his tracks-stone dead. Quickly the murderer dragged the corpse into the black shadows within the hangar. Then he returned to the flier.

Drawing a cunningly wrought key from his pocket-pouch, he removed the cover of the right-hand dial of the controlling destination compass. For a moment he studied the construction of the mechanism beneath. Then he returned the dial to its place, set the pointer, and removed it again to note the resultant change in the position of the parts affected by the act.

A smile crossed his lips. With a pair of cutters he snipped off the projection which extended through the dial from the external pointer-now the latter might be moved to any point upon the dial without affecting the mechanism below. In other words, the eastern hemisphere dial was useless.

Now he turned his attention to the western dial. This he set upon a certain point. Afterward he removed the cover of this dial also, and with keen tool cut the steel finger from the under side of the pointer.

As quickly as possible he replaced the second dial cover, and resumed his place on guard. To all intents and purposes the compass was as efficient as before; but, as a matter of fact, the moving of the pointers upon the dials resulted now in no corresponding shift of the mechanism beneath-and the device was set, immovably, upon a destination of the slave's own choosing.

Presently came Carthoris, accompanied by but a handful of his gentlemen. He cast but a casual glance upon the single slave who stood guard. The fellow's thin, cruel lips, and the sword-cut that ran from temple to mouth aroused the suggestion of an unpleasant memory within him. He wondered where Saran Tal had found the man— then the matter faded from his thoughts, and in another moment the Prince of Helium was laughing and chatting with his companions, though below the surface his heart was cold with dread, for what contingencies confronted Thuvia of Ptarth he could not even guess.

First to his mind, naturally, had sprung the thought that Astok of Dusar had stolen the fair Ptarthian; but almost simultaneously with the report of the abduction had come news of the great fetes at Dusar in honour of the return of the jeddak's son to the court of his father.

It could not have been he, thought Carthoris, for on the very night that Thuvia was taken Astok had been in Dusar, and yet-

He entered the flier, exchanging casual remarks with his companions as he unlocked the mechanism of the compass and set the pointer upon the capital city of Ptarth.

With a word of farewell he touched the button which controlled the repulsive rays, and as the flier rose lightly into the air, the engine purred in answer to the touch of his finger upon a second button, the propellers whirred as his hand drew back the speed lever, and Carthoris, Prince of Helium, was off into the gorgeous Martian night beneath the hurtling moons and the million stars.

Scarce had the flier found its speed ere the man, wrapping his sleeping silks and furs about him, stretched at full length upon the narrow deck to sleep.

But sleep did not come at once at his bidding.

Instead, his thoughts ran riot in his brain, driving sleep away. He recalled the words of Thuvia of Ptarth, words that had half assured him that she loved him; for when he had asked her if she loved Kulan Tith, she had answered only that she was promised to him.

Now he saw that her reply was open to more than a single construction. It might, of course, mean that she did not love Kulan Tith; and so, by inference, be taken to mean that she loved another.

But what assurance was there that the other was Carthoris of Helium?

The more he thought upon it the more positive he became that not only was there no assurance in her words that she loved him, but none either in any act of hers. No, the fact was, she did not love him. She loved another. She had not been abducted-she had fled willingly with her lover.

With such pleasant thoughts filling him alternately with despair and rage, Carthoris at last dropped into the sleep of utter mental exhaustion.

The breaking of the sudden dawn found him still asleep. His flier was rushing swiftly above a barren, ochre plain-the world-old bottom of a long-dead Martian sea.

In the distance rose low hills. Toward these the craft was headed. As it approached them, a great promontory might have been seen from its deck, stretching out into what had once been a mighty ocean, and circling back once more to enclose the forgotten harbour of a forgotten city, which still stretched back from its deserted quays, an imposing pile of wondrous architecture of a long-dead past.

The countless dismal windows, vacant and forlorn, stared, sightless, from their marble walls; the whole sad city taking on the semblance of scattered mounds of dead men's sun-bleached skulls-the casements having the appearance of eyeless sockets, the portals, grinning jaws.

Closer came the flier, but now its speed was diminishing-yet this was not Ptarth.

Above the central plaza it stopped, slowly settling Marsward. Within a hundred yards of the ground it came to rest, floating gently in the light air, and at the same instant an alarm sounded at the sleeper's ear.

Carthoris sprang to his feet. Below him he looked to see the teeming metropolis of Ptarth. Beside him, already, there should have been an air patrol.

He gazed about in bewildered astonishment. There indeed was a great city, but it was not Ptarth. No multitudes surged through its broad avenues. No signs of life broke the dead monotony of its deserted roof tops. No gorgeous silks, no priceless furs lent life and colour to the cold marble and the gleaming ersite.

No patrol boat lay ready with its familiar challenge. Silent and empty lay the great city-empty and silent the surrounding air.

What had happened?

Carthoris examined the dial of his compass. The pointer was set upon Ptarth. Could the creature of his genius have thus betrayed him? He would not believe it.

Quickly he unlocked the cover, turning it back upon its hinge. A single glance showed him the truth, or at least a part of it-the steel projection that communicated the movement of the pointer upon the dial to the heart of the mechanism beneath had been severed.

Who could have done the thing-and why?

Carthoris could not hazard even a faint guess. But the thing now was to learn in what portion of the world he was, and then take up his interrupted journey once more.

If it had been the purpose of some enemy to delay him, he had succeeded well, thought Carthoris, as he unlocked the cover of the second dial the first having shown that its pointer had not been set at all.

Beneath the second dial he found the steel pin severed as in the other, but the controlling mechanism had first been set for a point upon the western hemisphere.

He had just time to judge his location roughly at some place south-west of Helium, and at a considerable distance from the twin cities, when he was startled by a woman's scream beneath him.

Leaning over the side of the flier, he saw what appeared to be a red woman being dragged across the plaza by a huge green warrior-one of those fierce, cruel denizens of the dead sea-bottoms and deserted cities of dying Mars.

Carthoris waited to see no more. Reaching for the control board, he sent his craft racing plummet-like toward the ground.