In South Africa an old woman diagnosed with terminal cancer spends her last days writing a long, last letter to her daughter who lives in America. As death approaches she begins to look back on her life and her country. Her usual perception of events is challenged by association with some new people that have a closer relationship to the political turmoil raging in the country.

On the very day that she is informed that her ailment is incurable and that she will die soon, the narrator, former classics professor Mrs. Curren, finds a homeless man and his dog camped outside her home. Perhaps due to a combination of loneliness and fear after her recent diagnosis Mrs. Curren is less adamant than she once would have been about sending the man away. In a very short amount of time this homeless man named Mr. Vercueil who is certainly an alcoholic and possibly illiterate becomes the closest confidant of the former professor. Mrs. Curren tries to offer Mr. Vercueil money in exchange for work, but he is more interested in money for nothing and a constant supply of liquor. Still, over time the two begin to display genuine interest in each other beyond her immediate need of companionship and his immediate need for alcohol.

With the return of her live-in housekeeper, Florence, Mrs. Curren is exposed to aspects of her nation that she has perhaps known about and disagreed with but never before on a first-hand basis. First, Florence's teenage son, Bheki, arrives with his mother because Bheki has recently become politically active, and Florence fears that if she leaves him unsupervised in the township he will get into trouble. Soon one of Bheki's teenage friends arrives, and Mrs. Curren is able to see the brazen attitudes of the young generation of black South Africans. All her life Mrs. Curren has believed that aggressive activism, especially when it includes violence, is dangerous and harmful. Her well-defined views are first challenged when she witnesses the police brutally assault Bheki and his friend outside her house in an unprovoked assault.

The next major event to shake Mrs. Curren's worldview involves a trip to a township. The news media do not report on the violence and repression occurring in the townships, but Mrs. Curren sees first-hand the effects of waging war on a population already in poverty and living without hope. Her visit to the township culminates in viewing five dead bodies, one of which is a body of someone she knows. Deeply shaken, Mrs. Curren continues to question her own responsibility in the current sorry state of affairs.

After the incident in the township, Mrs. Curren begins to wonder if there is something she can do with the little bit of life she has left. With Mr. Vercueil as her confidant she considers a dramatic and martyr-like act. Fortunately, the shiftless vagrant also has a way of making her see the absurdity of some ideas. Before Mrs. Curren can act or achieve any sort of stability after the event witnessed at the township, another traumatic event occurs. The police storm her house and kill a teenager.

In the end, Age of Iron is both a novel about a dying woman trying to accept her own mortality and trying to understand her own responsibility in creating the society in which she lives.