hear Caron's men circling about through connecting tunnels,
searching. It proved what he had already guessed. He was taking a
desperate chance. But the way back was closed--and he was used to taking
chances.

The geography of the district was clear in his mind--the valley he had
just left and the main valley, forming an obtuse angle with the apex out
on the wind-torn plain and a double range of mountains lying out between
the sides of the triangle.

Somewhere there was a passage through 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," whisp