A sudden epidemic of blindness spreads throughout an unidentified country. When those who have lost their sight are examined, however, no evidence of pathology or damage can be found. The afflicted all describe "seeing" not darkness but rather a dense, impenetrable whiteness.

Because the government believes the disease is contagious, those people initially affected are quickly quarantined in a former mental hospital that is guarded by soldiers. There, the blind are treated like lepers and live like animals. Enigmatically, the wife of a sightless ophthalmologist has been spared from going blind. She functions as both protector and caregiver of a small group of blind people. They escape their imprisonment only when their captors (and presumably everyone except the ophthalmologist's wife) lose their sight.

Life is reduced to a constant search for food. As the situation grows even more grisly, vision is not only abruptly restored but perhaps with a clarity greater than ever before. When crowds of people rejoice "I can see," the reader wonders whether their earlier loss of sight was genuine or maybe some form of psychic blindness or spiritual malaise.