Nuclear testing in Earth’s orbit has left the human race sterile. Algy (Greybeard) and Martha are among the last children born.
Algy and Martha grow up and marry in a world that is slowly crumbling around them. The aging population seek security in barricaded camps as the infrastructure slowly collapses.
But Greybeard believes there is still hope for humanity, so he and his wife set out to find the children that he knows must exist. Children that dare not show their faces.