The voice was that of a woman, clear, musical, unutterably sweet--pathetically sad. It paused; spoke again. A new note crept into the words, ringing, thrilling: "Go your way--leave in peace, but travel far from this planet. The Mist of Mars will destroy all those who remain to despoil and murder here." Williams felt consciousness slipping from him once more. He struggled to speak. He must speak! These people must be told of his mission here! But his lips would not move. Struggle was useless. Feeling was gone from his body. The last sound he heard was the voice of a man, deep and full: "Heed the warning of the Mother of Mist. This once you have been spared." II Barry opened his eyes as the red sun climbed over the rim of the rolling desert. His head was clear, his mind refreshed and alert. These symptoms strengthened his convictions that he'd been hypnotized. The power of a highly trained mind was being used in this campaign against Earthmen. Perhaps the mist was produced both to hide the operator and to frighten the victim--making the latter easier prey to the force that invaded the brain, and had literally torn out the life essence of the other victims. Shrugging off further speculation for the moment, Barry climbed painfully to his feet. His muscles were stiff and cramped from lying hours on the ground. He flexed his arms and legs, worked his fingers, getting out the soreness. Then he started for his spaceship. As the rockets throbbed behind him, Barry tried all the controls. The little ship whipped through every intricate maneuver he'd ever known. It slowed his progress, this senseless stunting, but it showed him the ship was in prime condition, answering his every touch on the controls. Why was he doing this? It was as if he were going on a trip. Yet he had no such intention. The mist had spared him, and was gone. The mist! The thought brought the answer to his strange preparations--hypnosis again--post-hypnotic suggestion! Having spared him and ordered him to flee the planet, the being behind the mist had meant him to remember the advice. Barry's lips set in a straight line, and hard little muscles stood out on his cheek, along his strong jaw. He hadn't the slightest intention of fleeing Mars. He'd been sent here for a purpose by the Terrestrial Government, and he had come to realize the whole deadly threat of this Martian scourge against Earthmen was tied up with the reason for his being here. Barry William was staying on Mars till he'd finished his job. Below him, the circular, thick-walled, high-domed Center flashed over the horizon and loomed larger in the lower view-plate before Barry on the control board. Soon he was close enough to see the narrow apertures, where, in the early days of Terrestrial occupation, mighty ray cannon had blasted against bands of Martians who still had crude weapons to use against the victors.