As the bars of the cage smacked against the cement wall of the pit, John Carter's arms shot out with the quickness of a striking snake.

His fingers closed in a grip of steel about the ankle of the sleeping guard.

An ear-piercing shriek rang out across the arena, echoing dismally in the hollow crater, as the ape felt himself jerked suddenly from his slumbers.

Back swung the cage. Carter regrasped the shrieking ape with his other hand through the bars as they swung out over the water. The reptiles had to lower their heads as the cage moved over them so close had the water risen.

"Good work, John Carter," came Tars Tarkas's tense words as he reached out and grabbed hold of the ape with his four mighty hands. At the same time, Carter's cage splashed to a sudden stop. It had hit the water's surface.

"Hold him, Tars Tarkas. While I pull the key off the scoundrel's neck- there, I've got it!"

The water was flowing over the bottom of the cages. One of the reptiles had reached a horny arm in Dejah Thoris's cage and was attempting to snag her body with its sharp, hooked claws.

Tars Tarkas flung the ape's body with all the force of his giant thews straight at the reptile beside the girl's cage.

"Quickly, John Carter," cried Dejah Thoris. "Save yourself while they are fighting over the ape's body."

"Yes," echoed Tars Tarkas, "unlock your cage and get out while there is still time."

A half-smile lifted the corner of Carter's mouth as he swung open his prison door and leaped to the top of Dejah Thoris's cage.

"I'd sooner stay and die with you both," the earthman said, "than desert you now."

Carter soon had the princess' prison door unlocked but as he reached down to lift the girl up, a reptile darted forward into the cage with the princess.

In a quick second, Carter was inside the girl's cage, already knee-deep in water and he had hurled himself onto the back of the reptile. A steely arm was clamped tightly around the creature's neck. The head was jerked back just in time for the heavy jaws snapped closed only an inch from the girl's body.

"Climb out, Dejah Thoris-to the top of the cage!" ordered Carter. When she had obeyed, Carter dragged the flopping, helpless reptile to the cage door, as other slimy monsters started in. Using its body as a shield before him, the earthman forced his way to the door.

In an instant he had released his hold and vaulted up on top of the cage with the girl.

A moment later he had unlocked Tars Tarkas's cage door. After the green man had swung up beside them without mishap, the three climbed the ropes to the scaffolding above and then lowered themselves down to the ground beside the pit.

"Thank Issus," breathed the girl as they sat down to regain their breaths. Her beautiful head was cushioned upon Carter's shoulder, and he stroked her lovely black hair reassuringly.

Presently the earthman rose to his feet. Tars Tarkas had motioned him across the arena.

"There are some malagors left inside here," Tars Tarkas called from the entrance to the cavern inside the crater from where had come Pew Mogel's mounts.

"Good!" exclaimed Carter. "There may be a chance yet to reach and help Helium."

A moment later they had caught two of the birds and had risen over the ancient city of Korvas.

They spotted their planes on the outskirts of the city where they had left them the night they were tricked into being captured by Pew Mogel.

But to their disappointment, the controls had been destroyed irreparably, so they were forced to continue their journey on the backs of the malagors.

However, the malagors proved speedy mounts. By noon the next day the trio had reached the City of Thark, inhabited by a hundred thousand green warriors over whom Tars Tarkas ruled.

Gathering the warriors together in the marketplace, Tars Tarkas and John Carter explained the peril that confronted Helium and asked for their support in marching to their allies' aid.

As one man, the mighty warriors shouted their approval. The next day dawned upon a long caravan of thoat-mounted soldiers streaming out from the city gates towardsHelium.

A messenger was sent on a malagor to the Toonolian Marshes in an attempt to locate Kantos Kan and urge him to return home with his fleet to aid in the defense of Helium.

Tars Tarkas had abandoned his malagor to this messenger, in favour of a thoat upon which he rode at the head of his warriors. Directly above him, mounted on the other malagor rode Dejah Thoris and John Carter.

John Carter and Dejah Thoris, mounted upon their malagor, were scouting far ahead of the main column of advancing warriors when they first came in sight of the besieged City of Helium.

It was bright moonlight. The princess voiced a little, disappointed cry when she looked out across the spacious valley towards Helium. Her grandfather's city was completely surrounded by the besieging troops of Pew Mogel.

"My poor city!" The girl was crying softly, for in the bright moonlight below could be easily discerned the terrific gap in the ramparts and the many crushed and shattered buildings of the beautiful metropolis.

John Carter telepathically commanded the malagor to land upon a high peak in the mountains overlooking the Valley of Helium.

"Listen," cautioned John Carter. Pew Mogel's light entrenched cannon and small arms were commencing to open fire again by moonlight. "They are getting ready for an air attack."

Suddenly, from behind the two foothills between the valley and the towering peaks, there rose the vast, flying army of Pew Mogel.

"They are closing in from all sides," Dejah Thoris cried.

The great winged creatures and their formidable ape riders were swooping down relentlessly upon the city. Only a few of Helium's airships rose to give battle.

"Kantos Kan must have taken nearly all Helium's fleet with him," the earthman remarked. "I am surprised Helium has withstood the attack as long as this."

"You should know my people by now, John Carter," replied the princess.

"The infantry and anti-aircraft fire entrenched in Helium are doing well," Carter replied. "See those birds plummet to the ground."

"They can't hold out much longer, though," the girl replied. "Those apes are dropping bombs squarely into the city, as they swoop over, wave after wave of them-oh, John Carter, what can we do?"

John Carter's old fighting smile, usually present at times of personal danger, had given way to a stern, grave expression.

He saw below him the oldest and most powerful city on Mars being conquered by Pew Mogel's forces. Armed with Helium's vast resources, the synthetic man would go forth and conquer all the civilized nations on Mars.

Fifty thousand years of Martian learning and culture wrecked by a power-mad maniac, himself the synthetic product of civilized man!

"Is there nothing we can do to stop him, John Carter?" came the girl's repeated question.

"Very little, I'm afraid, my princess," he replied sadly, "All we can do is station Tars Tarkas's green warriors at an advantageous point in preparation for the counterattack and trust to fate that our messenger reached Kantos Kan in time that he may return and aid us."

"Without supporting aircraft, our green warriors, heroic fighters that they are, can do little against Pew Mogel's superior numbers in the air."

When John Carter and Dejah Thoris returned to Tars Tarkas, they reported what they had seen.

The great Thark agreed that his warriors could avail but little in a direct attack against Pew Mogel's air force. It was decided that half their troops be concentrated at one point and at dawn attempt to rush into the city.

The remaining half of the warriors would scatter into the mountains in smaller groups and engage the enemy in guerilla warfare.