Renzu probably had suffered the same fate as McFerson, Arlen decided. He was alone, in a strange world, face to face with a race of mankilling monsters. The only thing in his favor was that one of these monsters had befriended him. But how long and how far could Arlen trust this friendship? There was, however, a chance that McFerson or Renzu still might be living. He had to know for sure about this before he did anything else. And the only way to learn was to investigate. He left the ship, carefully closing the locks and fastening them behind him. He found many tracks leading away from the ship, along the banks of the stream that flowed from the mountains. From among the tracks he picked out Renzu's bootprints. There were tracks of Gheal going away, coming back, and going away again. He distinguished the two sets of Gheal's prints leading toward the mountains by the fact that one set was more deeply imprinted in the moist sand than the other. Gheal had been carrying McFerson's body. But what was this? There was another set of tracks coming toward the space ship. They were not Gheal's prints, for they were three toed. Gheal had five toes. Gheal and the creature who had attacked Arlen were different--one had three, the other five toes. Gheal might not have rescued Arlen out of gratitude after all. A natural enmity might have existed between the two races of Venusians. Arlen's rescue might have been an accident. Arlen studied. There was something else that fitted into the picture. If he could fit it correctly, he would have the answer. Somehow, now, he doubted if Gheal had rescued him out of gratitude; yet, he doubted if the rescue had been purely accidental. Arlen returned to the space ship and loaded a haversack with food. He was going into the mountains to get to the bottom of the mystery. He scribbled a note and left it in the control cabin in case Renzu or McFerson returned; if either were alive. <tb> The captain followed the stream into a deep-walled canyon opening into the mountains. A short distance from the ship he found Gheal's discarded trousers, indicating beyond a doubt that the Venusian had come this way after Arlen had been knocked unconscious in the sand. A mile or so farther on he saw a print where Gheal had placed McFerson on the ground. Then, a thrill of gratitude swept over Arlen, another set of boot prints appeared on the trail. McFerson was not dead. He was walking. The daylight was fading and Arlen realized he would not have much more time to follow the tracks without the aid of his flashlight. The walls of the gorge were almost perpendicular now and nearly a mile high on each side of the stream. The river boiled and churned over the barren rocks, but its movement was the only animation of the scene. Nowhere were there signs of life, excepting the footprints on the trail.