fact about them was that they couldn't contract any
disease. Not any.

They had a built-in, explosive reaction to bacterial and viral toxins,
and there hadn't yet been any pathogenic organism discovered to which
a _tormal_ could not more or less immediately develop antibody
resistance. So that in interstellar medicine _tormals_ were priceless.

Let 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, 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 to Dara
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 out-caste
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.

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 ele