At last he came to a stop on a rocky hillside, where the tracks were faint and indistinct. Carefully scanning the ground downslope, he saw that his instinct had not misled him--the caterpillar had turned aside at this place and had afterward returned to its original trail, backing and dragging its digging-blade to obliterate the traces of its side excursion. Dworn grinned, feeling the stirring of the hunter's excitement that never failed to move him, even on such a prosaic foraging expedition as this. He sent the beetle bumping down the slope. The blurred trail led into the sandy bed of a wash at the foot of the hill, and along that easily-traveled way for a quarter mile. Then the stream made a sharp bend, undercutting a promontory on the left and creating a high bank of earth and soft white rock. Dworn saw that a section of the bank had collapsed and slid into the gully. That was no accident; the mark where a great blade had sheared into the overhang was plain to read, even if it had not been for the scuffed over vestiges of caterpillar tracks round about. Dworn halted and listened intently, his amplifier turned all the way up. No sound broke the stillness, and the black moon-shadows within range of his vision did not stir. He nosed the beetle carefully up to the heap. He had no equipment for moving those tons of soil and rock, but that was no matter. He twisted a knob on the control panel, a shutter in the beetle's forward cowling snapped open and a telescoping drill thrust from its housing, chattered briefly and took hold, while the engine's pulse strengthened to take up the load. Twice Dworn abandoned fruitless borings and tried a different spot. On the third try, at almost full extension the drill-point screeched suddenly on metal and then as suddenly met no more resistance. Dworn switched on the pump, and quickly turned it off again; he swung the overhead hatch open, and--pausing to listen warily once more--clambered out onto the cowling, in the cold night air, to open the sample tap at the base of the drill and sniff the colorless fluid that trickled from it. It gave off the potent odor of good fuel, and Dworn nodded to himself, not regretting his caution though in this case it had not been needed. But--clever caterpillars had been known to bury canisters of water in their caches, poison for the unsuspecting. * * * * * The pump throbbed again; there was the satisfying gurgle of fuel flowing into almost-empty tanks. Dworn leaned back, seizing the opportunity to relax for a moment in preparation for the strenuous journey still before him. But he didn't fail to snap alert when just as the gauge trembled near the full mark, he heard pebbles rattling on the hillside above. Immediately thereupon he became aware of the grind of steel on stone and the rumbling of an imperfectly muffled engine.