train the spider's guns on the hurtling attacker.

Puffs of smoke bloomed high in air--but any hit on such a fast-moving
target, from so unstable a platform, would have been a miracle. The
enemy screeched overhead, and an instant later flame and thunder erupted
all around the running spider. The machine stumbled and for a moment
seemed going down, but it righted itself and staggered on.

Dworn shook his ringing head and saw the flier banking steeply half a
mile away, while a second and a third were climbing against the sky,
gaining altitude to dive.

They couldn't last another thirty seconds, couldn't even hope to reach
the doubtful cover of the rocks.... Up ahead, two hundred yards, was a
low mound, only a few feet high, the only nearby elevation of any sort.
And it was plainly artificial, though wind-piled sand had softened its
outlines; others like it were scattered around the periphery of the
great sink, and Dworn guessed their nature as he saw a column of the
aluminum crawlers beginning to emerge from the side of the one just
ahead. It must be the other end of a tunnel such as they had discovered
among the cliffs....

He nudged Qanya urgently, shouted, "Head for that!"

She gave him a fleeting, wide-eyed look. The mound's low swell could
furnish no shelter for the towering spider, and the tunnel mouth was of
course much too small to enter. But she veered without slackening speed
in the direction indicated.

Dworn abandoned the useless guns. The mound, with a gleaming line of
crawlers still parading out of it, swept closer; and at the same time
the desert echoed back the screaming onrush of the two new attackers.

Dworn wrenched open the cabin door with one hand. His other arm circled
Qanya's waist, dragged her away from the controls. She cried in
uncomprehending shock as he swung her before him into the open doorway.
They swayed there, high above the speeding ground, wind whipping at them
as the spider pounded blindly on.

The mound loomed immediately at hand. Dworn prayed that he had judged
the moment right, and with a mighty leap launched both of them out into
space.

A pistoning steel leg barely missed them. Even as they fell, the air was
torn by explosions as the swooping fliers opened fire.

* * * * *

Dworn hit the ground with almost stunning force. His hold on the girl
was broken and he was rolled helplessly over and over by his own
momentum. But he fetched up on