"Something unusual has happened," said Maril, very much subdued. "I told you that—sometimes blueskin markings fade out on children, and then neither they nor their children ever have blueskin markings again."
"Yes," said Calhoun. "I remember."
"And you were reminded of a group of viruses on Tralee. You said they only took hold of people in terribly bad physical condition, but then they could be passed on from mother to child. Until—sometimes—they died out."
Calhoun blinked.
"Yes...."
"Korvan," said Maril very carefully, "Has worked out an idea that that's what happens to the blueskin markings on—us Darians. He thinks that people almost dead of the plague could get the—virus, and if they recovered from the plague pass the virus on and—be blueskins."
"Interesting," said Calhoun, noncommittally.
"And when we went to Weald," said Maril very carefully indeed, "you were working with some culture-material. You wrote quite a lot about it in the ship's log. You gave yourself an injection. Remember? And Murgatroyd? You wrote down your temperature, and Murgatroyd's?" She moistened her lips. "You said that if infection passed between us, something would be very infectious indeed?"
"What are you driving at?"
Maril continued slowly. "Th—thousands of people are having their pigment-spots fade away. Not only children but grownups. And—Korvan has found out that it always seems to happen after a day when they felt feverish and very thirsty—and then felt all right again. You tried out something that made you feverish and thirsty. I had it too, in the ship. Korvan thinks there's been an epidemic of something that—is obliterating the blue spots on everybody that catches it. There are always trivial epidemics that nobody notices. Korvan's found evidence of one that's making 'blueskin' no longer a word with any meaning."