Brennart thought it was a good omen, my first walk on the surface. Maybe it was, Doug thought. I could use a good omen now.

Suddenly Gordette's boot prints ended. Disappeared. Doug stopped, puzzled. He backtracked a few steps, then saw that Gordette had climbed down into the shallow gully cut into the ground by the rille. Turning on his helmet lamp, Doug spotted faint boot marks heading along the bottom of the rille, some two meters below the surface on which he stood.

The prints still headed in the same general direction that Gordette had been following. Why'd he jump down into the rille? Doug asked himself. Was he afraid I'd follow him and he's trying to hide his trail? The prints down inside the rille were faint, but still visible.

Staying on the surface, Doug followed the rille as it wound across the regolith. It could be dangerous down there, Doug told himself. The rilles are old fissures where gas from below ground had seeped out. The ground down there can be brittle as glass, and who knows what's underneath it?

Edith trundled along in the tractor, trying to keep its speed down to the pace of a walking man. The trail of boot prints was easy to see, and she didn't want Doug to know she following him. Not yet.

Once she thought she saw the curve of his helmet above the horizon, and she tromped on the tractor's brakes. If I can't see him, he can't see me, she figured. And he sure can't hear me coming after him, not out here in all this vacuum.

The nearness of the horizon bothered her. It didn't look right. She knew, consciously, that the Moon was only a quarter of the Earth's size and the horizon was therefore much closer than it would be on Earth. But still, at a deep, primitive level, it almost frightened her. As if there really was an edge to this barren, desolate world and she might drop off it.

Yeah, she told herself derisively, you're right in there with Columbus's crew. Sail on, babe. Sail on.

Doug didn't realize he still had the suit-to-suit frequency on until he started hearing strange sounds in his earphones. Gasps? Moans? The sounds came through for a moment, then disappeared, like ghosts vanishing into thin air.

Very thin air, around here, he told himself.

The rille had been getting progressively deeper, sinking more than four meters below the crater floor, Doug guessed.

It was hard to tell, and almost impossible to see if Gordette's boot prints were still marching along down there, even when he leaned carefully over the worn, rounded smooth edge of the rille to shine his helmet lamp on its bottom.

He came to a spot where a meteoroid had slammed into the ground just next to the rille, collapsing its side into a heap of rubble. Doug spent several minutes searching for bootprints; he found none. As far as he could see there were no prints on the other side of the narrow rille, either.