ce.

"We don't know what we're facing, but the fate of the race as well as
our own lives, seem to be in danger. The break in the dome might have
been accident, and the moving forms the imagination of fear. But we know
that over a thousand people were killed--whatever caused the trouble!"

The men went back to their domes to rest, and plan some means of
entering the deserted city, but were disturbed before they had time for
sleep.

_The agricultural dome had been attacked!_ The pounding had begun within
a short time of their arrival.

One thing was certain, the injured dome had been _attacked_! It was not
accident that the metal ceiling fell. _There were living beings in the
gases outside their civilization!_

The first dome had been attacked just after the space ship left for the
earth, and this attack came just after its return to the domes. There
was little doubt that movement of the ship had disturbed the serenity of
existence. Perhaps the gas creatures hadn't known what was beneath the
metal hives until the ship appeared.

The banging on the agricultural dome, _had to be stopped_! A hole would
let in the gas! Rifles, that had been brought back on the ship as
curiosities, were given to each earthman. They loaded them carefully
while they searched for some means of reaching the trouble.

When the leader of the dome heard what they were planning, he showed
them sealed openings to a space between the sections of metal, which
hadn't been used since the city was built. The dome was constructed in
three layers, for insulation, and to give added protection. It was like
a maze, to work their way toward the pounding through the network of
struts. At times they had to crawl on their hands and knees, at others
there were clearly defined passages.

They were afraid, and not ashamed to show it. They were hunting
creatures which they knew nothing about--didn't even know whether
bullets would affect them! They might face thinking beings, or forms of
life that only wanted to search in the domes for food. It was not a
pleasant thought.

Every rifle was cocked as they neared the source of the pounding. Every
nerve drawn to the finest point.

Suddenly Dick stopped. He was ahead of the others and first to glimpse
what they faced. He motioned to use the oxygen masks, as he fastened his
own in place.

As they crept closer, light glinted on the giant pointed hammer,
operated from beyond the outer layer of metal. It rose and f