At his death in 1985, Sherred left an unfinished sequel to Alien Island, which author Lloyd Biggle, Jr. completed and published as Alien Main. Set on Earth some two hundred years after aliens had nearly destroyed life on the planet, the novel finds descendants of the aliens returning to atone for the atrocities committed by their ancestors. They find that the inhabitants of Earth are now living in tribes, with no connections except for a common belief in a goddess, whose return they await. While reviewer Gerald Jonas deemed Alien Main "not very ambitious," he nevertheless found the work offers a "pleasant blend of surprise and predictability," concluding: "Books such as this are the nourishing bread and butter of science fiction."