This day they stopped stock-still for two hours while sphexes puzzled over the trail the bears had left. Huyghens discoursed on the need of an anti-scent, to be used on the boots of men and the paws of bears, which would make the following of their trails unpopular with sphexes. Bordman seized upon the idea and suggested that a sphex-repellant odor might be worked out, which would make a human revolting to a sphex. If that were done, humans could go freely about, unmolested. "Like stink-bugs," said Huyghens, sardonically. "A very intelligent idea! Very rational! You can feel proud!" And suddenly Bordman was not proud of the idea at all. They camped again. On the third night they were at the base of that remarkable formation, the Sere Plateau, which from a distance looked like a mountain range but was actually a desert table-land. It was not reasonable for a desert to be raised high, while lowlands had rain, but on the fourth morning they found out why. They saw, far, far away, a truly monstrous mountain-mass at the end of the long expanse of the plateau. It was like the prow of a ship. It lay, so Huyghens observed, directly in line with the prevailing winds, and divided them as a ship's prow divides the waters. The moisture-bearing air-currents flowed beside the plateau, not over it, and its interior was desert in the unscreened sunshine of the high altitudes. It took them a full day to get half-way up the slope. And here, twice, as they climbed, Semper flew screaming over aggregations of sphexes to one side of them or the other. These were much larger groups than Huyghens had ever seen before, fifty to a hundred monstrosities together, where a dozen was a large hunting-pack elsewhere. He looked in the screen which showed him what Semper saw, four to five miles away. The sphexes padded uphill toward the Sere Plateau in a long line. Fifty--sixty--seventy tan-and-azure beasts out of hell. "I'd hate to have that bunch jump us," he said candidly to Bordman. "I don't think we'd stand a chance." "Here's where a robot tank would be useful," Bordman observed. "Anything armored," conceded Huyghens. "One man in an armored station like mine would be safe. But if he killed a sphex he'd be besieged. He'd have to stay holed up, breathing the smell of dead sphex, until the odor'd gone away. And he mustn't kill any others or he'd be besieged until winter came." Bordman did not suggest the advantages of robots in other directions. At that moment, for example, they were working their way up a slope which averaged fifty degrees. The bears climbed without effort despite their burdens. For the men it was infinite toil. Semper, the eagle, manifested impatience with bears and men alike, who crawled so slowly up an incline over which he soared. He went ahead up the mountainside and teetered in the air-currents at the plateau's edge. Huyghens looked in the vision-plate by which he reported.