ner, five Plutonians shambled through.

These creatures were as the ancient wall sculptures had depicted them,
though a bit smaller than their ancestors. They were pale, almost white
in skin color, and their eyes were tiny sparks of red. They wore light
harnesses around their bodies, and two of them were carrying tools. They
spoke together in clacking bass voices. They shuffled loosely over the
ground on their four thin legs. Burl thought of them as ugly caricatures
of semi-humans.

When the creatures had passed, the three explorers darted out to where a
ramp spiraled to the lower levels. They started down in single file, but
it was too late.

Staring directly at them were two Plutonians who had come up from below.
The men pushed past, but not before a barking voice had cracked out an
order.

The Earthmen started to run down, followed by the scrabbling sounds of
their pursuers. The barking calls increased in volume.

From somewhere a booming sound began, repeated over and over. As the men
emerged on the floor below, they heard it repeated on every level. "The
alarm's out for us," called Haines, making no effort to keep his voice
down. "We've got to run for it!"

Laden with the remaining weapons and equipment, the three human beings
hurried on, but it soon became clear that four legs were better than
two, for the creatures were gaining on them.

They had forgotten they were lost. Now they sought only to get out of
sight and hide. They dropped their equipment as they ran, down halls,
through tunnels, skittering along sloping ramps, heading for what they
hoped would prove to be an exit.

Behind them an increasing crowd of Plutonians had collected, and
several times a spark of electronic power crackled and blazed against
the wall over their heads. The pursuers were armed.

Burl's lungs began to ache painfully. Close on the heels of his
companions he dashed into one room only to find a group of Plutonians
coming at him from the other side. His ears were deafened by the barking
noises and alarm boomings. He jumped to one side to avoid a Plutonian
standing directly in his path, and ran into a narrow tunnel. There was
an excited barking as the creatures followed him.

With a sinking heart, he realized that he was now alone. Haines and Russ
must have been cut off. He gasped for breath. Running in a tight space
suit, carrying his oxygen tanks, was hot and hard work. He did not dare
drop the tanks, for his only chance