sense his meaning. She turned and called: "Diego!"

A boy appeared in the door, a dark-skinned, sleepy-eyed boy of about eight. He yawned. Then, catching sight of the big Dutchman, he opened his eyes wide and smiled.

The boy was healthy-looking, alert, but the mark of the Venus Shadow was on his face. There was a faint mottling, a criss-cross of dead-white lines.

Mrs. Murillo spoke to him rapidly in Spanish and he nodded. She zipped him into a venusuit and fitted a small helmet on his head.

"Good luck, amigo," said Sanchez, shaking Jan's hand again.

"Thanks," replied Jan. He donned his own helmet. "I'll need it, if the trip over was any indication."

Jan and Diego made their way back down the chain to the groundcar. There was a score of men there now, and a few women. They let the pair go through, and waved farewell as Jan swung the groundcar around and headed back eastward.

It was easier driving with the wind behind him, and Jan hit a hundred kilometers an hour several times before striking the rougher ground of Den Hoorn. Now, if he could only find a way over the bluff raised by that last quake....

The ground of Den Hoorn was still shivering. Jan did not realize this until he had to brake the groundcar almost to a stop at one point, because it was not shaking in severe, periodic shocks as it had earlier. It quivered constantly, like the surface of quicksand.

The ground far ahead of him had a strange color to it. Jan, watching for the cliff he had to skirt and scale, had picked up speed over some fairly even terrain, but now he slowed again, puzzled. There was something wrong ahead. He couldn't quite figure it out.

Diego, beside him, had sat quietly so far, peering eagerly through the windshield, not saying a word. Now suddenly he cried in a high thin tenor:

"Cuidado! Cuidado! Un abismo!"

Jim saw it at the same time and hit the brakes so hard the groundcar would have stood on its nose had its wheels been smaller. They skidded to a stop.

The chasm that had caused him such a long detour before had widened, evidently in the big quake that had hit earlier. Now it was a canyon, half a kilometer wide. Five meters from the edge he looked out over blank space at the far wall, and could not see the bottom.

Cursing choice Dutch profanity, Jan wheeled the groundcar northward and drove along the edge of the abyss as fast as he could. He wasted half an hour before realizing that it was getting no narrower.

There was no point in going back southward. It might be a hundred kilometers long or a thousand, but he never could reach the end of it and thread the tumbled rocks of Den Hoorn to Oostpoort before the G-boat blastoff.

There was nothing to do but turn back to Rathole and see if some other way could not be found.

Jan sat in the half-buried room and enjoyed the luxury of a pipe filled with some of Theodorus Neimeijer's mild tobacco. Before him, Dr. Sanchez sat with crossed legs, cleaning his fingernails with a scalpel. Diego's mother talked to the boy in low, liquid tones in a corner of the room.

Jan was at a loss to know how people whose technical knowledge was as skimpy as it obviously was in Rathole were able to build these semi-underground domes to resist the earth shocks that came from Den Hoorn. But this one showed no signs of stress. A religious print and a small pencil sketch of Señora Murillo, probably done by the boy, were awry on the inward-curving walls, but that was all.

Jan felt justifiably exasperated at these Spanish-speaking people.

"If some effort had been made to take the boy to Oostpoort from here, instead of calling on us to send a car, Den Hoorn could have been crossed before the crack opened," he pointed out.

"An effort was made," replied Sanchez quietly. "Perhaps you do not fully realize our position here. We have no engines except the stationary generators that give us current for our