Murgatroyd be infected with however localized, however specialized an
inimical organism, and presently some highly valuable defensive
substance could be isolated from his blood and he'd remain in his usual
exuberant good health. When the antibody was analyzed by those
techniques of microanalysis the Service had developed,--why--that was
that. The antibody could be synthesized and one could attack any
epidemic with confidence.

The tragedy for Dara was, of course, that no Med Ship had come there,
three generations ago, when the Dara plague raged. Worse, after the
plague Weald was able to exert pressure which only a criminally
incompetent Med Service director would have permitted. But criminal
incompetence and its consequences was what Calhoun had been loaned to
Sector Twelve to help remedy.

He was not at ease, though. No ship arrived from Orede to bear out his
account of an attempt to get that lonely world evacuated before Weald
discovered it had blueskins on it. Maril had vanished, to visit or
return to her family, or perhaps to consult with the mysterious Korvan
who'd arranged for her to leave Dara to be a spy, and had advised her
simply to make a new life somewhere else, abandoning a famine-ridden,
despised, and outcast world. Calhoun had learned of two achievements
the same Korvan had made for his world. Neither was remarkably
constructive. He'd offered to prove the value of the second by dying of
it. Which might make him a very admirable character, or he could have a
passion for martyrdom,--which is much more common than most people
think. In two days Calhoun was irritable enough from unaccustomed hunger
to suspect the worst of him.

And there was Weald to worry about. Weald was hysterically resolved to
end what it considered the blueskin menace for once and for all. There
were parallels to such unreasoning frenzy even in the ancient history of
Earth. A word still remained in the dictionaries referring to it.
Genocide.

* * * * *

Meanwhile Calhoun worked doggedly; in the hospitals while the patients
were awake and in the Med Ship--under guard--afterward. He had hunger
cramps now, but he tested a plastic cube with a thriving biological
culture in it. He worked at increasing his store of it. He'd snipped
samples of pigmented skin from dead patients in the hospitals, and
examined the pigmented areas, and very, very painstakingly verified a
theory. It took an electron microscope