Lane slept until half an hour after dawn, ate, deflated the tent, folded it, stowed it, the battery, heater, food-box, and folding chair into his pack, threw away the plastic sack, shouldered the pack, and resumed his walk.

By noon the tracks faded out completely. It made little difference, for there was only one route the tanks could have taken. That was the corridor between the tubes and the trees. Now he saw what the two tanks had reported. The trees on his right began to look dead. The trunks and leaves were brown, and the ribs drooped.

He began walking faster, his heart beating hard. An hour passed, and still the line of dead trees stretched as far as he could see.

"It must be about here," he said out loud to himself.

Then he stopped. Ahead was an obstacle.

It was the tube of which Greenberg had spoken, the one that ran at right angles to the other two and joined them.

Lane looked at it and thought that he could still hear Greenberg's despairing cry.

That thought seemed to turn a valve in him so that the immense pressure of loneliness, which he had succeeded in holding back until then, flooded in. The blue-black of the sky became the blackness and infinity of space itself, and he was a speck of flesh in an immensity as large as Earth's land area, a speck that knew no more of this world than a newborn baby knows of his.

Tiny and helpless, like a baby...

No, he murmured to himself, not a baby. Tiny, yes. Helpless, no. Baby, no. I am a man, a man, an Earthman --

Earthman: Cardigan Lane. Citizen of the U.S.A. Born in Hawaii, the fiftieth state. Of mingled German, Dutch, Chinese, Japanese, Negro, Cherokee, Polynesian, Portuguese, Russian-Jewish, Irish, Scotch, Norwegian, Finnish, Czech, English, and Welsh ancestry. Thirty-one years old. Five foot six. One hundred and sixty pounds. Brown-haired. Blue-eyed, Hawk-featured, M.D. and Ph.D. Married. Childless. Methodist. Sociable mesomorphic mesovert. Radio ham. Dog breeder. Deer hunter. Skin diver. Writer of first-rate but far from great poetry. All contained in his skin and his pressure suit, plus a love of companionship and life, an intense curiosity, and a courage. And now very much afraid of losing everything except his loneliness.

For some time he stood like a statue before the three-foot high wall of the tube. Finally, he shook his head violently, shook off his fear like a dog shaking off water. Lightly, despite the towering pack on his back, he leaped up onto the top of the tube and looked on the other side, though there was nothing he had not seen before jumping.

The view before him differed from the one behind in only one respect. This was the number of small plants that covered the ground. Or rather, he thought, after taking a second look, he had never seen these plants this size before. They were foot-high replicas of the huge umbrella trees that sprouted from the tubes. And they were not scattered at random, as might have been expected if they had grown from seeds blown by the wind. Instead, they grew in regular rows, the edges of the plants in one row separated from the other by about two feet.

His heart beat even faster. Such spacing must mean they were planted by intelligent life. Yet intelligent life seemed very improbable, given the Martian environment.

Possibly some natural condition might have caused the seeming artificiality of this garden. He would have to investigate.

Always with caution, though. So much depended on him: the lives of the four men, the success of the expedition. If this one failed, it might be the last. Many people on Earth were groaning loudly because of the cost of Space Arm and crying wildly for results that would mean money and power.

The field, or garden, extended for about three hundred yards. At its far end there was another tube at right angles to the two parallel ones. And at this point the giant umbrella plants regained their living and shining blue-green color.

The whole setup looked to Lane very much like a sunken garden. The square formation of the high tubes kept out the wind and most of the felsite flakes. The walls held the heat within the square.

Lane searched the top of the tube for bare spots where the metal plates of the caterpillar tractors' treads would have scraped off the lichenoids. He found none but was not surprised. The lichenoids grew phenomenally fast under the summertime sun.

He looked down at the ground on the garden side of the tube, where the tractors had presumably descended. Here there were no signs of the tractors' passage, for the little umbrellas grew up to within two feet of the edge of the tube, and they were uncrushed. Nor did he find any tracks at the ends of the tube where it joined the parallel rows.

He paused to think about his next step and was surprised to find himself breathing hard. A quick check of his air gauge showed him that the trouble wasn't an almost empty tank. No, it was the apprehension, the feeling of eeriness, of something wrong, that was causing his heart to beat so fast, to demand more oxygen.

Where could two tractors and four men have gone? And what could have caused them to disappear?

Could they have been attacked by some form of intelligent life? If that had happened, the unknown creatures had either carried off the six-ton tanks, or driven them away, or else forced the men to drive them off.

Where? How? By whom?

The hairs on the back of his neck stood up.

"Here is where it must have happened," he muttered to himself. "The first tank reported seeing this tube barring its way and said it would report again in another ten minutes. That was the last I heard from it. The second was cut off just as it was on top of the tube. Now, what happened? There are no cities on the surface of Mars, and no indications of underground civilization. The orbital ship would have seen openings to such a place through its telescope --"

He yelled so loudly that he was deafened as his voice bounced off the confines of his helmet. Then he fell silent, watching the line of basketball-size blue globes rise from the soil at the far end of the garden and swiftly soar into the sky.

He threw back his head until the back of it was stopped by the helmet and watched the rising globes as they left the ground, swelling until they seemed to be hundreds of feet across. Suddenly, like a soap bubble, the topmost one disappeared. The second in line, having reached the height of the first, also popped. And the others followed.

They were transparent. He could see some white cirrus clouds through the blue of the bubbles.

Lane did not move but watched the steady string of globes spurt from the soil. Though startled, he did not forget his training. He noted that the globes, besides being semitransparent, rose at a right angle to the ground and did not drift with the wind. He counted them and got to forty-nine when they ceased appearing.

He waited for fifteen minutes. When it looked as if nothing more would happen, he decided that he must investigate the spot where the globes seemed to have popped out of the ground. Taking a deep breath, he bent his knees and jumped out into the garden. He landed lightly about twelve feet out from the edge of the tube and between two rows of plants.

For a second he did not know what was happening, though he realized that something was wrong. Then he whirled around. Or tried to do so. One foot came up, but the other sank deeper.

He took one step forward, and the forward foot also disappeared into the thin stuff beneath the red-yellow dust. By now the other foot was too deep in to be pulled out.

Then he was hip-deep and grabbing at the stems of the plants to both sides of him. They uprooted easily, coming out of the soil, one clenched in each hand.