Presently the powerful rays of its searchlight shot downward from the bow. They fell upon the landing-stage for a brief instant, revealing the figures of the Ptarthian guard, picking into brilliant points of fire the gems upon their gorgeous harnesses.

Then the blazing eye swept onward across the burnished domes and graceful minarets, down into court and park and garden to pause at last upon the ersite bench and the girl standing there beside it, her face upturned full toward the flier.

For but an instant the searchlight halted upon Thuvia of Ptarth, then it was extinguished as suddenly as it had come to life. The flier passed on above her to disappear beyond a grove of lofty skeel trees that grew within the palace grounds.

The girl stood for some time as it had left her, except that her head was bent and her eyes downcast in thought.

Who but Carthoris could it have been? She tried to feel anger that he should have returned thus, spying upon her; but she found it difficult to be angry with the young prince of Helium.

What mad caprice could have induced him so to transgress the etiquette of nations? For lesser things great powers had gone to war.

The princess in her was shocked and angered-but what of the girl!

And the guard-what of them? Evidently they, too, had been so much surprised by the unprecedented action of the stranger that they had not even challenged; but that they had no thought to let the thing go unnoticed was quickly evidenced by the skirring of motors upon the landing-stage and the quick shooting airward of a long-lined patrol boat.

Thuvia watched it dart swiftly eastward. So, too, did other eyes watch.

Within the dense shadows of the skeel grove, in a wide avenue beneath o'erspreading foliage, a flier hung a dozen feet above the ground. From its deck keen eyes watched the far-fanning searchlight of the patrol boat. No light shone from the enshadowed craft. Upon its deck was the silence of the tomb. Its crew of a half-dozen red warriors watched the lights of the patrol boat diminishing in the distance.

«The intellects of our ancestors are with us to-night,» said one in a low tone.

«No plan ever carried better,» returned another. «They did precisely as the prince foretold.»

He who had first spoken turned toward the man who squatted before the control board.

«Now!» he whispered. There was no other order given. Every man upon the craft had evidently been well schooled in each detail of that night's work. Silently the dark hull crept beneath the cathedral arches of the dark and silent grove.

Thuvia of Ptarth, gazing toward the east, saw the blacker blot against the blackness of the trees as the craft topped the buttressed garden wall. She saw the dim bulk incline gently downward toward the scarlet sward of the garden.

She knew that men came not thus with honourable intent. Yet she did not cry aloud to alarm the near-by guardsmen, nor did she flee to the safety of the palace.

Why?

I can see her shrug her shapely shoulders in reply as she voices the age-old, universal answer of the woman: Because!

Scarce had the flier touched the ground when four men leaped from its deck. They ran forward toward the girl.

Still she made no sign of alarm, standing as though hypnotized. Or could it have been as one who awaited a welcome visitor?

Not until they were quite close to her did she move. Then the nearer moon, rising above the surrounding foliage, touched their faces, lighting all with the brilliancy of her silver rays.

Thuvia of Ptarth saw only strangers-warriors in the harness of Dusar. Now she took fright, but too late!

Before she could voice but a single cry, rough hands seized her. A heavy silken scarf was wound about her head. She was lifted in strong arms and borne to the deck of the flier. There was the sudden whirl of propellers, the rushing of air against her body, and, from far beneath the shouting and the challenge from the guard.

Racing toward the south another flier sped toward Helium. In its cabin a tall red man bent over the soft sole of an upturned sandal. With delicate instruments he measured the faint imprint of a small object which appeared there. Upon a pad beside him was the outline of a key, and here he noted the results of his measurements.

A smile played upon his lips as he completed his task and turned to one who waited at the opposite side of the table.

«The man is a genius,» he remarked.

«Only a genius could have evolved such a lock as this is designed to spring. Here, take the sketch, Larok, and give all thine own genius full and unfettered freedom in reproducing it in metal.»

The warrior-artificer bowed. «Man builds naught,» he said, «that man may not destroy.» Then he left the cabin with the sketch.

As dawn broke upon the lofty towers which mark the twin cities of Helium-the scarlet tower of one and the yellow tower of its sister-a flier floated lazily out of the north.

Upon its bow was emblazoned the signia of a lesser noble of a far city of the empire of Helium. Its leisurely approach and the evident confidence with which it moved across the city aroused no suspicion in the minds of the sleepy guard. Their round of duty nearly done, they had little thought beyond the coming of those who were to relieve them.

Peace reigned throughout Helium. Stagnant, emasculating peace. Helium had no enemies. There was naught to fear.

Without haste the nearest air patrol swung sluggishly about and approached the stranger. At easy speaking distance the officer upon her deck hailed the incoming craft.

The cheery «Kaor!» and the plausible explanation that the owner had come from distant parts for a few days of pleasure in gay Helium sufficed. The air-patrol boat sheered off, passing again upon its way. The stranger continued toward a public landing-stage, where she dropped into the ways and came to rest.

At about the same time a warrior entered her cabin.

«It is done, Vas Kor,» he said, handing a small metal key to the tall noble who had just risen from his sleeping silks and furs.

«Good!» exclaimed the latter. «You must have worked upon it all during the night, Larok.»

The warrior nodded.

«Now fetch me the Heliumetic metal you wrought some days since,» commanded Vas Kor.

This done, the warrior assisted his master to replace the handsome jewelled metal of his harness with the plainer ornaments of an ordinary fighting man of Helium, and with the insignia of the same house that appeared upon the bow of the flier.

Vas Kor breakfasted on board. Then he emerged upon the aerial dock, entered an elevator, and was borne quickly to the street below, where he was soon engulfed by the early morning throng of workers hastening to their daily duties.

Among them his warrior trappings were no more remarkable than is a pair of trousers upon Broadway. All Martian men are warriors, save those physically unable to bear arms. The tradesman and his clerk clank with their martial trappings as they pursue their vocations. The schoolboy, coming into the world, as he does, almost adult from the snowy shell that has encompassed his development for five long years, knows so little of life without a sword at his hip that he would feel the same discomfiture at going abroad unarmed that an Earth boy would experience in walking the streets knicker-bockerless.

Vas Kor's destination lay in Greater Helium, which lies some seventy-five miles across the level plain from Lesser Helium. He had landed at the latter city because the air patrol is less suspicious and alert than that above the larger metropolis where lies the palace of the jeddak.

As he moved with the throng in the parklike canyon of the thoroughfare the life of an awakening Martian city was in evidence about him. Houses, raised high upon their slender metal columns for the night were dropping gently toward the ground. Among the flowers upon the scarlet sward which lies about the buildings children were already playing, and comely women laughing and chatting with their neighbours as they culled gorgeous blossoms for the vases within doors.