When the terraforming crews introduced the alien Quill to worlds where they did not belong, they saw them only as a mindless form of fungal life which acted as a harmless relaxant when worn by a human. They were supposed to be destroyed when the crews finished their work, but Quill filaments survived, multiplied, and mutated till they were no longer harmless. Suddenly mankind was in retreat, leaving colonists stranded in space. In the ensuing chaos many stations failed. For the survivors, the only hope lay in finding a way to wipe out the Quill. And Earth scientist, Dr. Gail Smith thought one special human, Aaron Pardell, might have the answer....