|Ace paperback, 1966. Cover painting by Jack Gaughan.|
"Virtually the only connecting links between the innumerable colonized planets were the med ships -- lone starships carrying only one man and one beast. These trained teams of super-medical engineers took their lives in their hands on every planetfall. And for the team of Calhoun and Murgatroyd, three calls for help meant three challenges beyond all the experiences of all their systems. Plague, mystery, and menace marked the missions -- and the human enemies they faced on each world were just as virulent as the microscopic ones. Murray Leinster, dean of science-fiction writers, is at his thought provoking best in this exciting space adventure."