"But what do you think they are?" she asked.

"There used to be a human disease called smallpox," said Calhoun.
"When people recovered from it, they were usually marked. Their skin
had little scar pits here and there. At one time, back on Earth, it
was expected that everybody would catch smallpox sooner or later, and
a large percentage would die of it.

"And it was so much a matter of course that if they printed a picture
of a criminal they never mentioned it if he were pock-marked. It was
no distinction. But if he didn't have the markings, they'd mention
that!" He paused. "Those pock-marks weren't hereditary, but otherwise
a blueskin is like a man who had them. He can't be anything else!"

"Then you think they're human?"

"There's never yet been a case of reverse evolution," said Calhoun.
"Maybe Pithecanthropus had a monkey uncle, but no Pithecanthropus ever
went monkey."

She turned abruptly away. But she glanced at him often during that
day. He continued to busy himself with those activities which make Med
Ship life consistent with retained sanity.

Next day she asked without preliminary, "Don't you believe the
blueskins planned for the ship with the dead men to arrive at Weald
and spread plague there?"

"No," said Calhoun.