The Planet Savers

The Planet Savers is a 1962 science fiction book by Marion Zimmer Bradley. It is part of her Darkover (a fictional world) series. Desperate to discover a cure for the cyclical 48-year-fever, known as Trailmen's fever, Dr. Randall Forth persuades a colleague, Dr. Jay Allison, to undergo hypnosis. He calls forth a secondary personality, Jason Allison, who is gregarious and an experienced mountain climber, while Dr. Jay Allison is a cold, clinical man with no outdoor skills... This is just the beginning of a fantastic internal adventure!