The air outside was lower in pressure than that inside the cargo nose of the rocket, which had been sealed at Earth level. But it was air and it was breathable. Robin drew in several deep lungfuls, savoring it.

It was oddly exhilarating, as if highly charged with oxygen. At the same time there was a smell of mold and dampness and a definite taste of sulfur and phosphorus like that just after a kitchen match has been lighted. Even so, the air was breathable.

Robin worked his head and shoulders through the narrow opening, slid forward and landed on hands and knees on the rocky surface. He got to his feet, looked around.

He was standing on the bank of a rushing stream of water, which was pouring out of a large gap in the side of a cliff. The cliff ran straight up, gently curving to form part of the ceiling several hundred feet overhead. The extent of this ceiling was impossible to determine—it was dark and obscure—but it seemed to Robin almost at once that he was in some sort of gigantic enclosed space—a vast cavern beneath the surface of the Moon, probably several miles beneath it.

The water coming from the underground falls rushed out to form a wide, shallow river which flowed along one side of the cavern and widened out to a few hundred feet clear across to the farther wall. On Robin's side the floor of the cavern rose in a slow slope until it reached its wall perhaps three hundred feet away. Robin could not estimate the length of the cavern. Looking along the river bank, the cave seemed to become veiled in a general mistiness and gathering darkness.

The light itself came from no definite source, but seemed to emanate from the rocky walls and ceiling, from the clayey ground, and from the general atmosphere. Robin supposed that the source was a natural phosphorescence which he knew was not too uncommon even in Terrestrial caverns.

All around on the soil bordering the flowing water was a forest, a forest with the weirdest vegetation Robin had ever seen. Plants growing in clumps and clusters, plants whose large treelike stalks resembled a whitish-blue bamboo, and which burst into globular blue bulbs which seemed to serve as leaves. Among these tree-sized growths was a rich undergrowth of tight balls of varying yellow and green and purple, growing like thick, squat mushrooms. And everywhere else a thick, lush carpet of green, not grasslike but rather like some oversize moss.

In this forest there were no sounds of birds or animals, but only that of plants swaying in the river breeze, the rushing of the waters, and from somewhere distant in the unseen end of the cavern a strange, steady hissing sound.

The rocket, or what was left of it, lay wedged against a section of the bank, its nose up and its tail swaying in the current. Robin looked at it, amazed to find it so small. All that was left of the rocket was the cargo nose, which was the only part sent off after the last of the rocket sections had discharged their forces and been dropped off. The whole affair was not more than about ten feet long, from the battered, blunted red nose, from which several long, straggling orange cords hung—all that was left of the parachute and its attachments—down to the scraped and battered white cylinder that was the cargo compartment. The compartment ended in a flat plate which bore only a few wires that had once connected it with the break-away mechanism of the last of the atomic blasting chambers. This alone was the load of the eight-story tower of energy which had been the Red Sands experimental rocket.

Robin, without further delay, bent down to the cylinder and began to haul and push it entirely out of the water to the dry ground. He knew he could not afford to risk its loss. To his surprise, moving the rocket head was an easy task. It was extremely light and he found himself possessed of tremendous strength, tired and bruised and sore as he was.