d died away.
Revealed was a tunnel of utter blackness.

Tim Austin released his breath. The sound roused Nellon from the trance
which gripped him.

"It's probably controlled by an automatic mechanism. When we shoved
against it, we must have set that mechanism in motion."

"I'm going in, Brad," Big Tim said suddenly. "I'm going to see what's
inside." He strode impulsively to the door. But at the threshold he
stopped and turned and looked at Nellon.

Nellon smiled faintly and nodded. He strode after Big Tim. Together they
entered the doorway.

Lights, built into the helmets of their suits, but up to this time
unused, were turned on to illuminate the way. The tunnel, they saw, was
a rectangular corridor or passageway. It was lined with the same metal
as that of the door.

At two intervals down the corridor they found it necessary to squeeze
through half-opened doorways. The doors here were of the slide type and
seemed to be controlled by machinery as was the one which they had
opened to gain entrance to the corridor. But these could not be moved,
nor did their efforts awaken any hum of machinery.

"You know," Big Tim remarked, "this arrangement of doors sort of reminds
me of an airlock."

"I've noticed the same thing," Nellon responded. "But an airlock--" He
shook his head, for this was one of the many things he couldn't
understand.

Soon the corridor came to an end. Nellon and Austin found themselves in
a small, square room, each side of which was lined with small glass
cubicles or cabinets. In each reposed a transparent sphere with various
inexplicable attachments and a compactly folded mass of some strange
material.

"Helmets!" Big Tim breathed. "Brad, those are helmets. And unless I'm
mistaken the other stuff must be suits of some kind. What have we
stumbled onto, anyway?"

Nellon passed a slow, almost-knowing glance about the room, his helmet
lights glinting on the glass of the cabinets.

"I've got a crazy idea," he said. "But let that wait until we see more.
There's another doorway over there. Let's go on."

* * * * *

They went on. There were more corridors, but this time there were rooms
opening from them. Each was uniformly alike, filled with the same
articles and furnishings. Nothing with which they were familiar had any
counterpart here. Everything, from strange, rounded furniture to bizarre
clothing, was weirdly alien.

But of the beings who had once inhabited