those peaks. Somewhere there was a landing place, and ten to one there was a ship on it. Caron would never have left his men stranded, on the off chance that they might be discovered and used in evidence against him.
The men now hunting him knew their way through the tunnels, probably with the aid of markings that fluoresced under infra-red light. They were going to take him through, too.
They were coming closer. He waited far up in the main gallery, in the mouth of a side tunnel. Now, behind them, he could hear Dio’s men. The noise of Caron’s outfit stopped, then began again, softly.
Gray smiled, his sense of humor pleased. He tensed, waiting.
*
The rustle of cloth, the furtive creak of leather, the clink of metal equipment. Heavy breathing. Somebody whispered,
“Who the hell’s that back there?”
“Must be men from the Project. We’d better hurry.”
“We’ve got to find that damned Gray first,” snapped the first voice grimly. “Caron’ll burn us if we don’t.”
Gray counted six separate footsteps, trying to allow for the echoes. When he was sure the last man was by, he stepped out. The noise of Dio’s hunt was growing--there must be a good many of them.
Covered by their own echoes, he stole up on the men ahead. His groping hand brushed gently against the clothing of the last man in the group. Gauging his distance swiftly, he went into action.
One hand fastened over the fellow’s mouth. The other, holding a good-sized rock, struck down behind the ear. Gray eased the body down with scarcely a sound.
Their uniforms, he had noticed, were not too different from his prison garb. In a second he had stripped goggles, cap, and gun-belt from the body, and was striding after the others.
They moved like five eerie shadows now, in the queer light of the leader’s lamp. Small fluorescent markings guided them. The last man grunted over his shoulder,
“What happened to you?”
“Stumbled,” whispered Gray tersely, keeping his head down. A whisper is a good disguise for the voice. The other nodded.
“Don’t straggle. No fun, getting lost in here.”
The leader broke in. “We’ll circle again. Be careful of that Project bunch--they’ll be using ordinary light. And be quiet!”
They went, through connecting passages. The noise of Dio’s party grew ominously loud. Abruptly, the leader swore.
“Caron or no Caron, he’s gone. And we’d better go, too.”
He turned off, down a different tunnel, and Gray heaved a sigh of relief, remembering the body he’d left in the open. For a time the noise of their pursuers grew remote. And then, suddenly, there was an echoing clamor of footsteps, and the glare of torches on the wall of a cross-passage ahead.
Voices came to Gray, distorted by the rock vaults.
“I’m sure I heard them, just then.” It was Jill’s voice.
“Yeah.” That was Dio. “The trouble is, where?”
The footsteps halted. Then, “Let’s try this passage. We don’t want to get too far into this maze.”
Caron’s leader blasphemed softly and dodged into a side tunnel. The man next to Gray stumbled and cried out with pain as he struck the wall, and a shout rose behind them.
The leader broke into a run, twisting, turning, diving into the maze of smaller tunnels. The sounds of pursuit faded, were lost in the tomblike silence of the caves. One of the men laughed.
“We sure lost '>em!”
“Yeah,” said the leader. “We lost '>em, all right.” Gray caught the note of panic in his voice. “We lost the markers, too.”
“You mean...?”
“Yeah. Turning off like that did it. Unless we can find that marked tunnel, we’re sunk!”
Gray, silent in the shadows, laughed a bitter, ironic laugh.
*
They went on, stumbling down endless black halls, losing all track of branching corridors, straining to catch the first glint of saving light. Once or twice they caught the echoes of Dio’s party, and knew that they, too, were lost and wandering.
Then, quite suddenly, they came out into a vast gallery, running like a subway tube straight to left and right. A wind tore down it, hot as a draught from the burning gates of Hell.
It was a moment before anyone grasped the significance of that wind. Then someone shouted,
“We’re saved! All we have to do is walk against it!”
They turned left, almost running in the teeth of that searing blast. And Gray began to notice a peculiar thing.
The air was charged with electricity. His clothing stiffened and crackled. His hair crawled on his head. He could see the faint discharges of sparks from his companions.
Whether it was the effect of the charged air, or the reaction from the nervous strain of the past hours, Mel Gray began to be afraid.
Weary to exhaustion, they struggled on against the burning wind. And then they blundered out into a cave, huge as a cathedral, lighted by a queer, uncertain bluish light.
Gray caught the sharp smell of ozone. His whole body was tingling with electric tension. The bluish light seemed to be in indeterminate lumps scattered over the rocky floor. The rush of the wind under that tremendous vault was terrifying.
They stopped, Gray keeping to the background. Now was the time to evade his unconscious helpers. The moment they reached daylight, he’d be discovered.
Soft-footed as a cat, he was already hidden among the heavy shadows of the fluted walls when, he heard the voices.
They came from off to the right, a confused shout of men under fearful strain, growing louder and louder, underscored with the tramp of footsteps. Lights blazed suddenly in the cathedral dark, and from the mouth of a great tunnel some hundred yards away, the men of the Project poured into the cave.
And then, sharp and high and unexpected, a man screamed.
*
The lumps of blue light were moving. And a man had died. He lay on the rock, his flesh blackened jelly, with a rope of glowing light running from the metal of his gun butt to the metal buttons on his cap.
All across the vast floor of that cavern the slow, eerie ripple of motion grew. The scattered lumps melted and flowed together, converging in wavelets of blue flame upon the men.
The answer came to Gray. Those things were some form of energy-life, born of the tremendous electric tensions on Mercury. Like all electricity, they were attracted to metal.
In a sudden frenzy of motion, he
