The sombre story of a group of people in their fifties who face the fact that there is no younger generation coming to replace them; instead nature is rushing back to obliterate the disaster they have brought on theselves.

Distinguished by excellence of style and poetic intensity of vision, Greybeard is science fiction with a difference. Brian W. Aldiss posits a future in which mankind and most other mammals have been rendered sterile because of a cosmic "Accident" in 1981. By 2029 "large organizations had gone the way of large animals; the hedges grew, the copses heaved their shoulders and became forests; the rivers spread into marshland; and the mammal with the big brain eked out his dotage in small communities".