God!" gasped Burton.

We stared at him.

"The ship," he whispered. "It's right in line with the holes! If whatever made them is still in operation...."

"Run!" yelled Allenby, and we ran like fiends.

We got the ship into the air, out of line with the holes to what we fervently hoped was safety, and then we realized we were admitting our fear that the mysterious hole-maker might still be lurking around.

Well, the evidence was all for it, as Gonzales had reminded us—that cactus had been oozing.

We cruised at twenty thousand feet and thought it over.

Janus, whose only training was in photography, said, "Some kind of omnivorous animal? Or bird? Eats rocks and everything?"

"I will not totally discount the notion of such an animal," Randolph said. "But I will resist to the death the suggestion that it forages with geometric precision."

After a while, Allenby said, "Land, Burton. By that 'canal.' Lots of plant life—fauna, too. We'll do a little collecting."

Burton set us down feather-light at the very edge of the sprawling flat expanse of vegetation, commenting that the scene reminded him of his native Texas pear-flats.

We wandered in the chilly air, each of us except Burton pursuing his specialty. Randolph relentlessly stalked another of the rabbity creatures. Gonzales was carefully digging up plants and stowing them in jars. Janus was busy with his cameras, recording every aspect of Mars transferable to film. Allenby walked around, helping anybody who needed it. An astronomer, he'd done half his work on the way to Mars and would do the other half on the return trip. Burton lounged in the Sun, his back against a ship's fin, and played chess with Allenby, who was calling out his moves in a bull roar. I grubbed for rocks.

My search took me farther and farther away from the others—all I could find around the 'canal' was gravel, and I wanted to chip at some big stuff. I walked toward a long rise a half-mile or so away, beyond which rose an enticing array of house-sized boulders.

As I moved out of earshot, I heard Randolph snarl, "Burton, will you stop yelling, 'Kt to B-2 and check?' Every time you open your yap, this critter takes off on me."

Then I saw the groove.

It started right where the ground began to rise—a thin, shallow, curve-bottomed groove in the dirt at my feet, about half an inch across, running off straight toward higher ground.

With my eyes glued to it, I walked. The ground slowly rose. The groove deepened, widened—now it was about three inches across, about one and a half deep.

I walked on, holding my breath. Four inches wide. Two inches deep.

The ground rose some more. Four and three-eighths inches wide. I didn't have to measure it—I knew.

Now, as the ground rose, the edges of the groove began to curve inward over the groove. They touched. No more groove.

The ground had risen, the groove had stayed level and gone underground.

Except that now it wasn't a groove. It was a round tunnel.

A hole.

A few paces farther on, I thumped the ground with my heel where the hole ought to be. The dirt crumbled, and there was the little dark tunnel, running straight in both directions.

I walked on, the ground falling away gradually again. The entire process was repeated in reverse. A hairline appeared in the dirt—widened—became lips that drew slowly apart to reveal the neat straight four-inch groove—which shrank as slowly to a shallow line of the ground—and vanished.

I looked ahead of me. There was one low ridge of ground between me and the enormous boulders. A neat four-inch semicircle was bitten out of the very top of the ridge. In the house-sized boulder directly beyond was a four-inch hole.

Allenby winced and called the others when I came back