had not been built to offset attack from the
surface of the planet itself. It was no thick rampart of unbroken
plastic as the walls of the other Sun-tap stations had been. Close up,
it proved to have many doorless entryways, ramps running up to higher
floors, even wiry monorail scaffolding, probably left behind by the
builders.

They entered an opening in the base. Once inside, dim lights set in the
ceiling lighted the path before them. They walked down this culvert like
rats in a giant sewer until they came to a wall studded with several
doors.

The doors were shut, but a tiny globe set on the surface of each one
reacted to Burl's charged touch. Two opened upon dark airless passages.
The third resisted a moment, and when it did open, there was a whoosh of
air which raised a momentary cloud of dust on the stone floor of the
culvert. This was obviously the entrance to the inhabited portion of the
refuge.

The men closed the door behind them. They were in a small chamber. A
door on the other side was opening automatically. "An air lock system,"
muttered Russ as they went through.

They were now inside the vast building itself. There was air, and, after
testing it, they opened their helmets. The air was almost as thick as
that of Earth, and they experienced no difficulty in breathing. It was
stale and somewhat metallic in flavor, probably because it had been
enclosed and used over and over for thousands of years.

They saw no living beings, which seemed strange. "Apparently these
people really are at their last gasp," remarked Russ as they passed
through an area that had obviously once been a large dormitory. They
heard distant humming sounds somewhere in the floors above, but all that
was visible on the lower level seemed to be maintenance machinery.

They walked through great storerooms which were piled high with sealed
drums. They saw factories lying silent--curious lofts of odd machines
powered by globes that were idle. They skirted an unlighted reservoir of
water in a circular chamber far in the interior. And here and there in
the gloom, they spotted huge ramps leading spirally upward.

Finally they turned their steps up a sloping ramp, mounting one floor
and then another, and another. They were tired, but curiously
exhilarated. They felt that they were about to strike at the heart of
the foe, and that his days were numbered at last.

They emerged on a higher level, lighted more brightly than the others.
Her