The next morning they said goodbye to Tabor and watched the _Sunbeam_ lift into the Martian sky. For a moment Nathan wondered if they were right. If Tabor should actually be heading for Venus-- Since the _Corsair_ was being repaired they had a logical reason for preparing to go to the Pater Mountains by sand sled, besides the secret purpose of making it easy to trail them. They made elaborate preparations. They visited every supply store in the Five Cities, pricing and examining sand sleds and boldly discussing their reason for wanting one. By the time their equipment was assembled every spaceman in Taurus knew of their purpose and destination. And the word passed to the other towns on Mars as well. It was a late afternoon two days later when they left Taurus. Firebird proposed a late start in order to make it easy for anyone to follow them. Since their destination was well known they anticipated ambush from ahead as well as trailing from behind. Nathan climbed into the narrow seat of the sand sled beside Firebird. She took the wheel because she was familiar with the trail to the Mountains. When the transparent cowling was closed over them they seemed to be in a tiny, separate world all their own. Behind, the muffled roar of the propeller cut the air and mounted in intensity as the sled began to move forward and the runners hissed against the sand. Firebird handled the sled as if any vehicle that traveled slower than a space ship was much too slow for her. She soon had the sled up to top speed over the level area near Taurus and soon they were weaving among the giant dunes. The great, shifting dunes of the Martian desert were forty to fifty feet high. Already the valleys between them were filled with purple shadows and the air was turning cold. The sled dipped and careened; sometimes it plunged into deep sand valleys and whipped around the curved walls of deep blow holes until it was tipped almost at right angles, clinging only by centrifugal force. Nathan had the impression that Firebird was enjoying it. The treachery of the desert was a challenge to her skillful, daredevil driving. Soon the sun was down and the pale light of the twin moons was deceptive on the sands. Firebird slowed the plunging flight of the sled and drove cautiously then until near midnight. "We should be somewhere near the town of Pheme, such as it is," she said. "The last time I saw it, it was almost a ghost town. It may have been completely abandoned by now." "I've never heard of it," said Nathan. In a moment Firebird exclaimed, "There it is! How's that for navigation over this desert? Right on the nose." Nathan laughed at Firebird's exuberance over her accuracy. He knew that it was no small job to follow such an unmarked trail across the sands that shifted constantly and made landmarks impossible.