Dr. Jay Allison was a surgeon specializing in the parasitology of the planet Darkover. Antiseptic hospital walls were the limits of his world - the virgin ranges of the planet, and its people, were abhorrent to him. Jason was Dr. Allison's exact opposite - headstrong and impulsive. Raised by the semi-human Trailmen, he loved Darkover as his only known home. A deadly epidemic threatened the planet, and epidemic that would destroy both Terran and Darkovan civilization, and the only hope for a cure lay somewhere in the unknown vastness of Trailmen territory. Only Jason could lead them safely through that dangerous land, and only Jay Allison could develop the cure - but it was impossible for them to work together...for both minds shared one body.