This is rather a disturbing and uncompromising novel! I remember when I first read it that I rather lost the will to live because of the grim and unyielding vision of humanity that it presents us with, so beware. However, at the same time, it is an incredible novel, and the way that Saramago produces works that are so richly allegorical and comment upon our contemporary society is a true wonder.
The novel begins with one man suddenly being struck by blindness. He is "helped" by another man who uses this as an opportunity to abuse the blind man's position to steal from him. The man goes to see an eye-doctor who is able to find no explanation for the man's blindness. However, slowly and insidiously, this mysterious blindness continues to spread to different people, striking the eye-doctor and other people that the first man had contact with. Shocked by this mysterious illness, the government round up all those effected and place them in quarantine, abandoning the victims together and leaving armed soldiers around them to ensure that nobody escapes. The eye-doctor's wife, in spite of not being blind, pretends that she is so that she can go with her husband and look after him.
Days pass and the numbers of people who are added to this strange community because of the blindness increase. A group of men seize power and take control of the food, forcing women from the different rooms to have sex with them in exchange for food. The doctor's wife herself endures this, until she uses her sight to kill the leader of this group of men. Another woman starts a fire that kills many of these men.
When the doctor and his wife try to alert the authorities to what has happened, they exit and realise that they have been abandoned. The doctor's wife leads her husband and a group of survivors into a city where everyone has been struck blind, and looks after them, finding food for them and caring for them. Finally, the first man who was struck blind regains his sight, which clearly indicates that this was just a temporary condition.