When Ray Osborne, a young American photographer, was precipitated suddenly from the twentieth century into a prehistoric age, he did not know that he had blundered into the field of an experimental time machine. But he soon realized that the new world was a hostile one when he was captured by a strange group of hunters, speaking no language he had ever heard. Only after he met the Murian, Cho, and was able to communicate with him telepathically, did he learn that they were both prisoners of the ruthless city-state Atlantis, which was preparing for war against the golden kingdom of Mu. Once they had managed to escape, Ray was increasingly aware that he could not avoid taking part in the coming struggle, but the nature of that part, and its magnitude, was not revealed to him until he had witnessed incredible horrors in the enemy's stronghold. Then at last he understood the justice of the cause he was serving and accepted the fate thrust upon him. With the extraordinary imagination and the deep concern for the nature of good and evil that distinguish The X Factor and other worlds of this leading science fiction writer, Andre Norton has developed from an ancient myth another taut and thrilling tale.