Following the defeat of his little army, Ras Thavas had disappeared and been all but forgotten as are the dead, among which he was numbered by those who had known him; but there were some who could never forget him. There was Valla Dia, Princess of Duhor, whose brain he had transferred to the head of the hideous old Xaxa, Jeddara of Phundahl, that Xaxa might acquire the young and beautiful body of Valla Dia. There was Vad Varo, her husband, one time assistant to Ras Thavas, who had restored her brain to her own body-Vad Varo, who had been born Ulysses Paxton in the United States of America and presumably died in a shell hole in France; and there was John Carter, Prince of Helium, Warlord of Mars, whose imagination had been intrigued by the tales Vad Varo had told him of the marvelous skill of a world's greatest scientist and surgeon.

John Carter had not forgotten Ras Thavas, and when an emergency arose in which the skill of this greatest of surgeons was the sole remaining hope, he determined to seek him out and find him if he still lived. Dejah Thoris, his princess, had suffered an appalling injury in a collision between two swift airships; and had lain unconscious for many weeks, her back broken and twisted, until the greatest surgeons of all Helium had at last given up all hope. Their skill had been only sufficient to keep her alive; it could not mend her.

But how to find Ras Thavas? That was the question. And then he recalled that Vad Varo had been the assistant of the great surgeon. Perhaps, if the master could not be found, the skill of the pupil might be adequate. Then, too, of all men upon Barsoom, Vad Varo would be most likely to know the whereabouts of Ras Thavas. And so John Carter determined to go first to Duhor.