over. It dropped down like a falling snake and disappeared, lying flat and straight by his feet and dropping flat and straight down in the blackness. Next, he took a finding and read off the depth of the hole. The door had ceased its slow sinking movement, and the readout matched the computer projection exactly.

John joined Phillip at the edge when he got the all clear signal. He stood beside his leader, silently. Comments were superfluous.

"I'll go first," said Phillip, "You watch me down. If there's any trouble, get back to the Vehicle and radio to Earth. Sorry to put so much on you, but I think they'll have to know sooner or later, and it might as well be from us first! Besides, by the time anyone gets here we'll have had a good look around!"

John nodded.

Phillip dropped his lower body over the edge of the wall and held the rope. He had no trouble going down, being only about one 10th his Earth weight, and soon he was almost out of sight. The sharp, straight shadow of the hole cut diagonally across his body, eating him up as he went.

As soon as his head disappeared into the pitch darkness, Phillip switched on his head lamp. He looked around for a moment, and then continued to hand over hand down the hole. His feet touched something hard and he knew he was either standing on the door, or on the floor of the hole.

It turned out he was on both. The door had slid down into a square hole in the floor of a large, polygonal room. He flashed his torch to John, who quickly began to come down the rope, and was soon standing beside him.

"Out of one mystery, into another?" said John, as he looked around.

"There must be a way out of this room," replied Phillip. He began to push on the walls. One of them had markings which looked like writing across it, and a red area, shaped like an oval. John pushed on it, and a slight vibration ran through his fingers. The wall slid to one side.

They stepped through, and found themselves standing on the edge of what looked like a road. It had a two-lane central strip, and slightly raised narrow bands along the edges. Small glass globes were set into the ceiling at regular intervals, and two large, round pieces of what might have been colored glass stood to one side of the wall.

"Looks like a road?" said John.