e fire. He
stared out into the western darkness, listening to the racket. He made
a wry face and pushed a hand absent-mindedly through his hair. He put
out a silent hope that the screamers would decide to keep their
distance. They were something a man could do without.

Behind him, a pebble came bumping down the slope. It thudded to a rest
just short of the fire.

Duncan spun around. Foolish thing to do, he thought, to camp so near
the slope. If something big should start to move, they'd be out of
luck.

He stood and listened. The night was quiet. Even the screamers had
shut up for the moment. Just one rolling rock and he had his hackles
up. He'd have to get himself in hand.

He went back to the boulder, and as he stooped to pick up the rifle,
he heard the faint beginning of a rumble. He straightened swiftly to
face the scarp that blotted out the star-strewn sky--and the rumble
grew!

* * * * *

In one leap, he was at Sipar's side. He reached down and grasped the
native by an arm, jerked it erect, held it on its feet. Sipar's eyes
snapped open, blinking in the firelight.

The rumble had grown to a roar and there were thumping noises, as of
heavy boulders bouncing, and beneath the roar the silky, ominous
rustle of sliding soil and rock.

Sipar jerked its arm free of Duncan's grip and plunged into the
darkness. Duncan whirled and followed.

They ran, stumbling in the dark, and behind them the roar of the
sliding, bouncing rock became a throaty roll of thunder that filled
the night from brim to brim. As he ran, Duncan could feel, in dread
anticipation, the gusty breath of hurtling debris blowing on his neck,
the crushing impact of a boulder smashing into him, the engulfing
flood of tumbling talus snatching at his legs.

A puff of billowing dust came out and caught them and they ran choking
as well as stumbling. Off to the left of them, a mighty chunk of rock
chugged along the ground in jerky, almost reluctant fashion.

Then the thunder stopped and all one could hear was the small
slitherings of the lesser debris as it trickled down the slope.

Duncan stopped running and slowly turned around. The campfire was
gone, buried, no doubt, beneath tons of overlay, and the stars had
paled because of the great cloud of dust which still billowed up into
the sky.

He heard Sipar moving near him and reached out a hand, searching for
the tracker, not knowing exactly where it was. He found