"Something strange 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 markings again."
"Yes," said Calhoun. "I remember that you told me."
"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 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?"
"This is a long discussion," said Calhoun. "Does it arrive at a point?"
"It does," said Maril. "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."