"Listen, I've spent hours figuring this out. Suppose one of us were to stay here in this cave, helmet-light on, and near enough to the opening so that his light would show dimly on the outside. Wouldn't a Mart guard be sure to come along to investigate?"
"Yes, practically sure," agreed Calbur, but with no great interest. Hour by hour he was sinking closer to that animate coma which gripped the other Earthmen. "But what would that get you? If you lose too much time, you'll be cut off from rations."
"I know, but suppose also that one of us—I, for instance—was hiding in the rocks above the cave, with a big chunk of ore, ready to heave it down on the Mart?"
Calbur seemed to be thinking this over, and for a moment there was silence.
"When shall we try it?" he demanded suddenly, and there was a note of eagerness and hope in his voice. "It's simple enough. It might actually work."
"Right now! If we put it off, it'll soon be too late."
They discussed details, laying their plans carefully, Bormon prudently refraining any suggestion that this move was one born of sheer desperation on his part.
Everything settled, Calbur moved up near the opening, so that his helmet-light could be dimly seen from outside the cave. Bormon, dragging his ore-basket, climbed up in the rocks directly over the entrance, and presently found concealment that suited him. Near at hand he placed a loose chunk of rock which on Earth would have weighed perhaps eighty pounds. The trap was set.
He settled himself to wait. His own light was, of course, extinguished. Far off he could see crawling blobs of luminance as guards and human workers moved slowly over the surface of Echo. Otherwise stygian darkness surrounded him. But he had chosen a position which, he hoped, would not be revealed by the light of any Martian bent on investigating the cave.
There were, he had learned, actually less than a score of Martians here on Echo; about half of them stayed around that cyclotronic ore-hurler in the chasm. They depended on secrecy, and were in constant communication, by ether-wave, with spies not only on Earth and Mars but among the personnel of the space police itself. These spies were in a position to warn them to shut down operations in case the ore stream through space attracted notice and was in danger of being investigated. It was all being conducted with true Martian insidiousness.