But he was still smiling toward that dark roof overhead as the outlines of a metal door grew cherry red. They were coming for him! He was ready to meet whatever lay ahead.... CHAPTER IX _A Subterranean World_ The metal plate that had sealed him in this tomb fell open with a crash. Beyond it the passageway was alive with crowding red figures. Above their heads the nozzles of a score of flame-throwers spat jets of green fire. Rawson drew back in sudden uncontrollable horror as they came crowding into the room. The familiar feel of the bailer's cold metal had given him a momentary sense of oneness with his own world. Now this inrush of hideous, demoniac figures beneath the flare of green flames was like a fevered vision of the infernal regions come suddenly to actuality. Rawson retreated to the shattered, rocky wall and prepared for one last fight, until he realized that the evil black eyes in their ghastly circles of white skin were fixed upon him more in curiosity than in active hatred. They formed a semicircle about him--a wall of red bodies, whose pointed heads were craned forward, while an excited chatter in their broken, whistling speech filled the room with shrill clamor. Then one of them pointed above toward the open shaft that Rawson had drilled, the shaft up which the bailer had gone. And again their voices rose in weird discord, while their long arms waved, and red, lean-fingered hands pointed. Only a moment of this, then one of them gave an order. Two of the red figures came toward Rawson where he was waiting. They were unarmed. They motioned that he was to go with them. And Dean, with a helpless shrug of his shoulders, allowed them, one on each side, to take him by the arms and hurry him through the open door. Two others went ahead, the green jets of flame from their weapons lighting the passage. The system of communicating tunnels seemed at first only the vents and blow-holes from some previous volcanic activity. And yet, at times they gave place to more regular arrangement that plainly was artificial. The air in them was pure, though odorous with a pungent tang which Dean could not identify. Through some of the passages it blew gently with uncomfortable warmth. The guard of wild red figures hurried him along through a vast world of caverns and winding passages which seemed one great mine. The richness of it was amazing. Dean Rawson was a man, a human being, facing death in some form which he could not yet know, and, so fast had his wild experiences crowded in upon him, he seemed numbed to all normal emotions; yet through it all the mind of the engineer was at work, and Dean's eyes were flashing from side to side, trying to see and understand the ever-changing panorama of a subterranean world. * * * * * Mole-men, both red and yellow, were everywhere. But it was apparent at a glance that the yellow giants were a race of toilers--slaves, driven by the reds.