Captain Walls motioned Kenniston and Holk Or angrily toward the ship. "Bray, take them in and lock them under guard in a cabin," he said. Holk Or suddenly yelled. "Look out! There's a Vestan!" Kenniston, his blood chilling with alarm, glanced where the Jovian pointed. At the west edge of the clearing, a small animal had suddenly emerged from the dense green jungle. It was a six-legged, striped, catlike beast, not unordinary as interplanetary animals go. But its head looked queer, seeming to have a bulbous gray mass attached behind its ears. Captain Walls uttered a scoffing exclamation. "That's only an ordinary asteroid-cat." "That _is_ a Vestan!" Kenniston cried. "Shoot at its head--" His warning was too late. The catlike beast had launched itself in a spring toward their group. As its striped body shot through the air, Walls triggered his atom-pistol. The crackling blast of force tore into the body of the charging asteroid-cat, and the beast fell heavily a few yards away. But as it fell, the small gray mass upon its neck suddenly detached itself from the dead animal and scuttled swiftly forward. It moved with blurring speed toward Bray, the nearest to it of the group. The little gray creature was no bigger than a man's clenched fists together. It was a gray, wrinkled featureless thing, except for pinpoint eyes and the tiny clawlike legs upon which it scurried. It reached Bray and ran swiftly up his legs and back as he swore startledly. Kenniston, made reckless of danger by his horror, yelled and lunged toward the pilot. Bray was swearing and trying to slap at the gray thing running up his back. But the little creature had now reached his neck. Clinging there, it swiftly dug two tiny, needle-like antennae into the base of his neck. "Hold him!" Kenniston shouted hoarsely. "The Vestan has got him!" Bray had undergone a sudden metamorphosis as the gray creature dug its antennae into his neck. His face stiffened, became masklike. The pilot turned and began to run stiffly toward the jungle. Kenniston's leap almost caught him, but Bray lashed out a fist that sent Kenniston sprawling. "Don't let him get away!" Kenniston yelled, scrambling up. But the others were too stricken by amazement and horror to interfere in time. Bray had already plunged into the jungle and was gone. "My God, what happened?" Captain Walls exclaimed dazedly. "Bray went clean crazy!" His gun was pointing at Kenniston and Holk Or as though he held them responsible for what had occurred. "He didn't go crazy, but he's lost now," Kenniston said heavily. "That little gray creature was one of the Vestans." "But what did it _do_ to him? That thing wasn't big enough to harm anybody." "That's all you know about it," said Holk Or ominously. "Those little Vestans are the most dangerous creatures in the System."