The condition shown by the landing-grid suspicions was a case in point.  Blueskins were people who inherited a splotchy skin pigmentation from other people who’d survived a plague.  Weald plainly maintained a one-planet quarantine against them.  But a quarantine is normally an emergency measure.  The Med Service should have taken over, wiped out the need for a quarantine, and then lifted it.  It hadn’t been done.

Calhoun fumed to himself.

The world of Weald Three grew brighter and brighter and became a disk.  The disk had icecaps and a reasonable proportion of land and water surface.  The ship decelerated, voices notifying observation from the surface, and the little ship came to a stop some five planetary diameters out from solidity.  The landing field’s force-field locked on to it, and its descent began.

The business of landing was all very familiar, from the blue rim which appeared at the limb of the planet from one diameter out, to the singular flowing-apart of the surface features as the ship sank still lower.  There was the circular landing-grid, rearing skyward for nearly a mile.  It could let down interstellar liners from emptiness and lift them out to emptiness again, with great convenience and economy for everyone.

It landed the Med Ship in its center, and there were officials to greet Calhoun, and he knew in advance the routine part of his visit.  There would be an interview with the planet’s chief executive, by whatever title he was called.  There would be a banquet.  Murgatroyd would be petted by everybody.  There would be painful efforts to impress Calhoun with the splendid conduct of public health matters on Weald.  He would be told much scandal.

He might find one man, somewhere, who passionately labored to advance the welfare of his fellow humans by finding out how to keep them well or, failing that, how to make them well when they got sick.  And in two days, or three, Calhoun would be escorted back to the landing-grid, and lifted out to space, and he’d spend long empty days in overdrive and land somewhere else to do the whole thing all over again.

It all happened exactly as he expected, with one exception.  Every human being he met on Weald wanted to talk about blueskins.  Blueskins and the idea of blueskins obsessed everyone.  Calhoun listened without asking questions until he had the picture of what blueskins meant to the people who talked of them.  Then he knew there would be no use asking questions at random.

Nobody mentioned ever having seen a blueskin.  Nobody mentioned a specific event in which a blueskin had at any named time taken part.  But everybody was afraid of blueskins.  It was a patterned, an inculcated, a stage-directed fixed idea.  And it found expression in shocked references to the vileness, the depravity, the monstrousness of the blueskin inhabitants of Dara, from whom Weald must at all costs be protected.

It did not make sense.  So Calhoun listened politely until he found an undistinguished medical man who wanted some special information about gene selection as practised halfway across the galaxy.  He invited that man to the Med Ship, where he supplied the information not hitherto available.  He saw his guest’s eyes shine a little with that joyous awe a man feels when he finds out something he has wanted long and badly to know.