The integral trees

For a long, long time the State used slower-than-light spacecraft to prepare star systems for colonization by Man. Normally the ramseeders traveled centuries-long circuits which began and ended at Earth. Normally the mixed crew of citizens and "corpsicle" convicts remained with their ship. Normally ultimate control of the mission was exercised by a built-in cyborg "adviser", the true despot of the tiny State microcosm that was the ship.
But little happened normally when Discipline reached the double-star system of T3 and LeVoy's Star. There an immense doughnut-shaped gaseous envelope had formed around a neutron star--and a vast volume of that nearly empty cloud was comfortably habitable to Man. Though it had very little usable land, the Smoke Ring had evolved a huge variety of free-fall life-forms, most of which were edible and all of which could fly.

The Smoke Ring seemed a paradise to the restless crew of Discipline and so they fled to it, leaving behind only the ship and Sharls Davis Kendy, the ship's cyborg cop. Five centuries passed, and most of the mutineers' descendants forgot about the Earth, the State, even Discipline. But Sharls Davis Kendy never forgot about the humans, and somewhere, just outside the Smoke Ring, he waited...