They call them the "rat-catchers." They're the crew of the spaceship Daedalus, which an economically destitute Earth has dispatched on a mission to re-establish contact with its far-flung, long-lost colonies in space. Alex Alexander, the ship's biologist, together with his staff, must help solve the mysteries of human and alien ecosystems that he encounters light-years from home.

Dendra is a stable world, covered by a huge, unchanging forest—except that nothing living can really be free of change. The planet has no seasons, but its animal life still undergoes life-cycles involving birth, maturation, metamorphosis, and death. The Earth colony sent to tame the world has failed, at least in the terms expected of it, and seems beyond redemption; but the crew of the Daedalus still has to find out exactly why and how the program has gone wrong. Provided, of course, that they can survive the investigation itself!