Age of Iron begins with Mrs. Curren learning of her terminal cancer diagnosis. This personal crisis is set against the broader crisis of Apartheid, which she has largely ignored in her life of academic privilege as a Classics professor. The novel takes the form of letters that Mrs. Curren writes to her daughter, who lives in America and whom Mrs. Curren doesn’t want to tell about her illness. She hopes her letters will reach her daughter after she dies, and that they’ll help her daughter understand both Mrs. Curren’s final weeks and Apartheid.
When Mrs. Curren arrives home from her oncology appointment, she discovers a homeless man, Vercueil, sleeping outside her home. At first, Mrs. Curren tries to send Vercueil away. However, they soon begin a friendship, and Mrs. Curren pays Vercueil to do some chores around the house. Usually, Vercueil only does half of what Mrs. Curren asks him, but she still pays him anyway.
After Mrs. Curren gets used to Vercueil’s presence, her housekeeper, Florence, returns from Guguletu, where she has been living with her children. Florence brings her teenage son, Bheki, back with her because the schools in Guguletu have closed due to the large-scale violence occurring there. Bheki is a teenager who wants to be involved in the resistance, and he begins bringing his friend, John, around the house, which makes Mrs. Curren uncomfortable. One day, Bheki and John have a dangerous encounter with the police, which lands John in the hospital. The event is a wake-up call to Mrs. Curren, who cannot believe how poorly law enforcement treats Black South Africans. Following this, Bheki becomes increasingly radicalized, and he goes to Guguletu to join the resistance. Florence and Mrs. Curren go looking for him, only to find him dead.
Meanwhile, the relationship between Mrs. Curren and Vercueil continues to evolve. Initially, Vercueil is a disheveled, often inebriated drifter, but he gradually becomes a constant companion to Mrs. Curren. He listens to her fears about death and her reflections on a life lived in a deeply divided country. Still, his character remains an enigma: sometimes he seems like her guardian angel, while at other times he appears violent and menacing.
After being discharged from the hospital following his encounter with law enforcement, John returns to Mrs. Curren’s home. John wants to go to Guguletu, but Mrs. Curren insists that he stay put for the time being, so he does not end up dead. She tries to contact people who might help him, but no one comes. Mrs. Curren becomes increasingly worried when she learns that John is stashing guns in her house. One day, the police coming knocking on Mrs. Curren’s door, looking for John. Mrs. Curren tries to protect John, but she fails: the police knock down John’s door and kill him. The incident leaves Mrs. Curren delirious, and she goes wandering out into the streets. There, young people assault and mug her while she is still in a dazed state. Luckily, Vercueil finds her and returns her to her home.
As Mrs. Curren’s illness advances, her reflections become more introspective and philosophical. She grapples with the meaning of her life and her role in a society riddled with injustice. Her narrative is punctuated by her attempts to reconcile with her daughter, who remains a distant figure because she has started her own life in America and does not plan to return to South Africa until Apartheid is over. Mrs. Curren begins spending more time with Vercueil and even invites him to sleep in her bed to help keep her warm. Vercueil does what he can to keep Mrs. Curren as comfortable as possible and promises to help her end her life when the time comes. One night, Mrs. Curren wakes up to find cold air blowing into her room. Vercueil is standing on the balcony letting the air blow into the bedroom. Mrs. Curren asks Vercueil, “Is it time?” Rather than respond, Vercueil climbs in bed and violently embraces her. His embrace feels cold.