Marnus Erasmus is an eleven-year-old boy who lives with his family—his mother, father, and older sister Ilse—in a suburb of Capetown, South Africa. It is the summer of 1974 and Marnus is excited for school to be out and the family vacation to begin; he is hoping to be considered old enough for an all-day fishing trip with his father. Marnus loves living by the bay and can see whales in the ocean (though they are not as frequent as they once used to be) from his bedroom window on the third floor of the house.
Marnus' father, a high-ranking general in the South Africa Defence Force, has high expectations for his family, the chief of these being that they do not disagree with any of his core beliefs. Because Marnus' grandfather was driven from his home in Tanganyika by black Africans he is determined to never let a situation like that arise in South Africa. He also despises communists.
Marnus' father has many guests from overseas who are on the side of the South Africans and their current guest is a general from Chile whom Marnus and Ilse are instructed to call “Mr. Smith” to preserve secrecy. Marnus likes Mr Smith and thinks his sister has a crush on him, although the general seems to be attracted to Marnus' mother.
Marnus' best friend is a boy from his class at school called Frikke Delport. They spend the majority of their free time together and particularly enjoy fishing. They invite Mr Smith and Marnus' father to meet them at the bay to fish but the two men are late so the boys start fishing without them. Marnus begins to reel in a fish they soon realize is a shark; the battle between them is intense and the shark is stronger than the boy. As he is wading into the water and grappling with the line, his father and the general arrive. Marnus desperately wants his father to help him reel the fish in but instead his father tells him to stop crying at once and to catch the shark without any more messing about. The shark wins the contest and Marnus fails to reel it in. His father is angry that Marnus has embarrassed him. Marnus is upset to have failed in front of the general whom he desperately wants to impress. He is fascinated by him and wants his approval.
Marnus' bedroom is above the guest room and he can see into it if he looks through a knot hole in one of the floorboards. Peering through one evening he notices a large scar that runs almost the length of the general's back and desperately wants to ask him what it is a result of.
School is finally out; the Erasmus' housekeeper, Doreen, is eagerly awaiting the arrival of her youngest son, Little-Neville, who is at the best Coloured school in the state. He is not on the train the first day he is expected, or the second, or the third. Doreen travels up to try to find him but when she arrives discovers that he has been burned with hot oil by white Afrikaaners and is fighting for his life in hospital. The event has a strong effect on both Marnus and his sister, and as Ilse is already starting to see that some of what she has been taught about black Africans is wrong. The event also leads to some heated words with her mother who toes the line completely when it comes to doing as her husband tells her.
The entire family attend Ilse's high school prize-giving where she plays the national anthem on the piano and also wins Head Girl for the following year. This is extremely prestigious but a teacher confides in their mother that some of the faculty did not want Ilse to be head girl, as she has become argumentative and started to show some rather controversial opinions of late.
As the Erasmus family will not leave for their summer cottage until the following Monday, Frikke is sleeping over for the weekend. It is also the general's last night with the family so Marnus' father decides to show him some slides of Tanganyika and also of himself and his wife in their younger years. The children love the slides as much as the adults do and both Frikke and Marnus fall asleep on the couch.
Marnus awakens to find that it is the early hours of the morning and that his mother had put a blanket over Frikke and himself rather than waking them to go upstairs to bed. Assuming Frikke is in the bathroom Marnus goes upstairs but in passing the bathroom sees it is empty and assumes Frikke already went to bed. Frikke is not in bed upstairs; a growing feeling of dread building inside him, Marnus peeps through the hole in the floorboards. He is scared in case the general did not leave after the slide show as planned and that Frikke will tell him that Marnus shared the general’s true identity with Frikke. Marnus also suspects that his sister and the general are involved.
He is shocked to see the figure of the general on the bed in the guest room with Frikke on the bed next to him, backed up against the wall, looking petrified. The general fondles Frikke's penis before placing the boy's hand on his own and, as Marnus watches silently above, climbs on top of him from behind and rapes him. Marnus decides to fetch his father immediately. He is also stunned that the general doesn't appear to have his scar anymore. Marnus runs to his parents' bedroom but his father isn't there. The horrible realization hits Marnus and he goes back to bed; Frikke comes upstairs a little while later and climbs into the second bed without a word. Marnus pretends to be asleep.
The following morning neither boy wants breakfast so they each grab an apple. Frikke says his smells sour and when Marnus smells it he agrees; Frikke takes a second apple and says this one is rancid as well but when Marnus smells it too he cannot find anything wrong with it. They realize it is Frikke's hand that smells but when Marnus asks him what he has touched Frikke says he does not know. Marnus realizes Frikke is not going to tell him about his father's abuse and Marnus is relieved because it means that he can still love his father and act like the incident didn't happen.
The story that young Marnus tells is interspersed with twenty-six-year-old Marnus' narration from the war zone in the neighboring nation of Angola where the South African army is fighting another country's war against a common Cuban enemy. Marnus leads his troops out of the danger zone and they make it to safety a few meters from the border but just as they believe they are safe Cuban pilots fly overhead and fire directly at them. It appears to be an attack nobody can survive—including Marnus.