no water or atmosphere to rust it. Not even a wind to disturb its surface. It's at least several thousand years old."

We slowly circled the alien structure. Several minutes later, Kane shouted, "Look!"

A few feet above the ground, the structure's smooth surface was broken by a circular opening that yawned invitingly. Kane ran ahead and flashed his head-lamp into the dark recess.

"There's a small room inside," he told us, and climbed through the opening.

We waited outside and focused our lamps through the five-foot opening to give him as much light as possible.

"Come on in, Marie," he called to his wife. "This is really something! It must be an alien race. There's all kinds of weird drawings on the walls and gadgets that look like controls for something...."

Briefly, my lamp flickered over Marie's pale face. Her features struggled with two conflicting emotions: She was frightened by the alienness of the thing and yet she wanted to be with her husband. She hesitated momentarily, then climbed through the passage.

"You want to go in?" my wife asked.

"Do you?"

"Let's."

I helped Verana through the opening, climbed through myself and turned to help Miller.

Miller was sixty years old. He was an excellent mineralogist, alert mentally, but with a body that was almost feeble. I reached out to help him as he stepped into the passageway.

For a brief second, he was framed in the opening, a dark silhouette against the star-studded sky.

The next second, he was thrown twenty yards into the air. He gasped with pain when he struck the ground. "Something pushed me!"

"Are you all right?"

"Yes."

He had fallen on a spot beyond our angle of vision. I started through the passage....

... and struck an invisible solid wall.

My eyes were on the circular opening. A metal panel emerged from a recess on one side and slid across the passage. The room darkened with the absence of starlight.

"What happened?"

"The door to this damned place closed," I explained.

"What?"

Before we could recover from the shock, the room filled with a brilliant glare. We turned off our lamps.

The room was approximately twelve feet long and nine feet wide. The ceiling was only a few inches above our heads and when I looked at the smooth, hard metal, I felt as if I were trapped in some alien vault.

The walls of the room were covered with strange drawings and instruments. Here and there, kaleidoscopic lights pulsed rhythmically.

Kane brushed past me and beat his gloved fists against the metal door that had imprisoned us.

"Miller!"

"Yes?"

"See if you can get this thing open from the outside."

I knelt before the door and explored its surface with my fingers. There were no visible recesses or controls.

Over the intercom network, everyone's breath mingled and formed a rough, harsh sound. I could discern the women's quick, frightened breaths that were almost sobs. Kane's breath was deep and strong; Miller's was faltering and weak.

"Miller, get help!"

"I'll—" The sound of his breathing ceased. We listened intently.

"What happened to him?"

"I'll phone Lunar City." My fingers fumbled at the radio controls and trembled beneath the thick gloves.

I turned the dials that would connect my radio with Lunar City....

Static grated against my ear drums.

Static!

I listened to the harsh, erratic sound and my voice was weak by comparison: "Calling Lunar City."

"Static!" Kane echoed my thoughts. His frown made deep clefts between his eyebrows. "There's no static between inter-lunar radio!"

Verana's voice was small and frightened. "That sounds like the static we hear over the bigger radios when we broadcast to Earth."

"It does," Marie agreed.

"But we wouldn't have that kind of static over our radio,