The Grass is Singing is set in Southern Rhodesia (now Zimbabwe) during the 1940s. Mary Turner, the wife of Dick Turner, has been murdered, and a “houseboy” has confessed to the crime. Dick and Mary are poor and do not socialize with the other white settlers in their farming district. When Mary’s body is discovered, the Turners’ neighbor, Charlie Slatter, sends a note to the local police sergeant, Sergeant Denham. Denham then sends six native policemen to the Turners’ farm, and shortly after they arrive the houseboy, Moses, turns himself in. Charlie drives to the Turners’ farm to find Moses in handcuffs, and puts Dick in the back of his car.
Inside the house, Charlie’s assistant Tony Marston explains that he found Mary’s body on the veranda. Sergeant Denham arrives, and he and Charlie question Tony. However, Tony begins to feel that they are not actually interested in his testimony, and the interview ends abruptly. The policemen take Mary’s body to the car, and Tony is left wondering whether he should insist on telling Charlie and Sergeant Denham his theory about why Mary was killed. Moses will be hanged no matter what happens, but Tony wonders if by staying silent he is complicit in a “monstrous injustice.” The next day, Tony packs his things and leaves the farming district. The trial takes place and it is decided that Moses murdered Mary while drunk and hoped to steal valuables from her. Tony, meanwhile, briefly takes a job in copper mining, before reluctantly ending up in an office job.
Chapter 2 begins with a description of the stores that are distributed throughout southern Africa. They are simple establishments that sell food, clothes, and other necessities, operate as local post offices, and usually house a bar. Mary’s father, an alcoholic, would spend their family’s little money on liquor at the store, a fact that always caused arguments between Mary’s parents. Mary’s older brother and sister died of dysentery when she was a child, and the period of grief that followed was “the happiest time of her childhood,” when her parents briefly stopped squabbling. Mary was eventually sent to boarding school and decided to leave home at 16. Between the ages of 20 and 25, both Mary’s parents died, and she was thrilled to be left completely alone. She lived in a club for young women and worked as a personal secretary at an office.
As the years passed, Mary’s friends got married and had children, but Mary herself remained single, happy, and carefree. She was in denial about aging, and still dressed in “little-girl fashion.” She felt no desire to get married, but one day overheard some married friends of hers gossiping cruelly about the fact that she was not married, and was horrified to realize that this was what people thought of her. After this point, she briefly became engaged to a 55-year-old widower, but called it off when he tried to have sex with her.
Soon after this, Mary meets Dick briefly at the cinema, during one of Dick’s brief visits to town. Dick is a poor farmer whose bad luck has led his neighbors to nickname him “Jonah.” He is resistant to the idea of getting married due to his poverty, but cannot stop thinking of Mary. He works to the point of exhaustion over the next few months, and eventually appears at Mary’s door asking to marry her. She agrees, and they marry two weeks later.
When Mary first arrives at Dick’s farm, she finds the house “shut and dark and stuffy,” and is struck by the evidence of Dick’s intense loneliness. They have tea and engage in a polite but awkward conversation. They have sex, which is not as terrible as Mary feared it would be, although she also feels “nothing” during it. In the morning, Dick introduces Mary to his longtime black house servant, Samson. While Dick clearly feels affection for Samson, Mary is immediately affronted by Samson’s casual manner. Mary resolves to teach herself “kitchen kaffir,” the simplified version of the native Shona language that white settlers use to communicate with their black workers.
Mary uses her savings to purchase fabrics and other items for the house, and spends her days sewing and painting the house. One day, she comes to believe that Samson stole raisins she was saving to make pudding and becomes hysterical; despite Dick’s protests, she insists on taking the money out of Samson’s wages. Samson quits, which upsets Dick. They hire another servant, but before long he quits as well. Then they find yet another servant, this time one who is accustomed to working for white women and obeys Mary’s demands in a “blank, robotic” manner. However, in a fit of emotion Mary forces the servant to spend hours scrubbing the (already clean) zinc bathtub, making him work through his lunch break. Charlie and Mrs. Slatter come over to visit; Mrs. Slatter is friendly to Mary, but Mary rebuffs her coldly. The servant quits. A few days later, Charlie advises Dick to plant tobacco, but Dick is resistant to this idea.
One day, on a rare visit to the local train station to pick up groceries, Dick and Mary encounter a man who addresses Dick as “Jonah”; afterward, Dick bitterly admits that he borrowed money from the man and still owes him £50. During this period, Dick goes through a series of obsessions with keeping different animals on the farm; first bees, then pigs, and then turkeys. All these experiments fail, and cause heated arguments between Dick and Mary. Dick begins jokingly calling Mary “boss,” which infuriates her.
Dick eventually resolves to open a “kaffir store” on the farm, even though there is a kaffir store nearby and thus it is unlikely that Dick’s store will make much money. He asks Mary to run the store; at first Mary says she “would rather die,” but she eventually agrees. Mary finds the native women who sit outside the store with their children disgusting and hates her time working there. She begins to fantasize about running away and returning to her old life in the town. One day, she notices that her old office has placed an ad for a shorthand typist. She packs a suitcase and leaves the next day, asking Charlie to drive her to the train station.
Back in town, Mary visits the girls’ club where she used to live, but is told that they do not take married women. At her old office, she is told that the typist position has been filled. Mary returns to her hotel room and realizes she doesn’t have enough money to pay the bill. At this moment, Dick arrives, and begs her to come home. Mary agrees.
At first Dick and Mary slip back into their previous routine; however, Dick soon becomes severely ill with a fever. Charlie brings over a doctor, who rudely instructs Mary that she and Dick must wire the house for mosquitoes and go on a three-month holiday to be restored back to health. During this time, Mary begins supervising the farm workers while Dick is bedridden. She takes a sambok with her, and when Moses (one of the farm workers) insists on getting a drink of water, she strikes him across the face with it. She also withholds wages from the workers who arrive late, causing some of them to quit on the spot. Back at the house, Mary urges Dick to focus on growing tobacco so they will be able to make enough money to leave the farm. Dick thinks about it for three days, before agreeing to start building tobacco barns.
Dick builds the tobacco barns, but in January there is a drought and the tobacco dies. Dick cannot cover the expenses, and is forced to take out a loan in order to avoid declaring bankruptcy. Mary’s health deteriorates. She begins to beg Dick for a child, but Dick refuses, saying that they are too poor. Mary sinks further and further into misery, as does Dick, who takes up chain-smoking. After another house servant leaves, Dick is forced to move Moses from the field to the house, as no one else will agree to work for Mary. Mary develops a fascination with Moses, watching him as he completes his work and even one day staring at him while he washes himself outside. He stops what he is doing and stares back at her until she goes away. This infuriates Mary, who forces Moses to do a series of unnecessary tasks. She asks Dick if they can fire Moses, but Dick angrily refuses.
Months pass, and Mary becomes increasingly depressed. One day, Moses tells her he is quitting, and she bursts into tears, begging him to stay. Moses gives her a glass of water, tells her to lie down on the bed, and covers her with her coat. He does not mention leaving again. A new dynamic then emerges between them; Moses is much more informal and authoritative with Mary, and Mary now feels completely under his power. During this period, Mary starts having vivid nightmares, while Dick becomes ill with malaria. She dreams that Dick has died, that Moses is touching her, and that her father is making sexual advances on her. In one dream, Moses and her father morph into the same figure, and she wakes up screaming. Moses asks her why she is afraid of him, and Mary replies in a hysterical voice that she is not afraid.
Meanwhile Dick and Mary’s neighbors have started spreading cruel gossip about them. One day, Charlie comes over, and urges Dick to sell his farm. Charlie stays for dinner, where he witnesses Moses and Mary’s familiar, flirtatious relationship. Charlie then takes Dick to one side and sternly demands that he and Mary leave. Dick reluctantly agrees, and Charlie asks Tony to start working on Dick’s farm in preparation to take over. While living on the Turners’ farm, Tony comes to believe that Mary has gone mad and needs to be treated by a psychologist. One day, he catches Moses helping Mary to get dressed, and is stunned by the possibility that they are having an affair. He decides to tell Dick to fire Moses, but Moses leaves that evening and does not return.
Two nights before Dick and Mary are due to leave the farm, Mary wakes up suddenly. She walks around the house in a state of paranoid delusion, swinging wildly between different emotional states. She looks for Moses, convinced that he will “finish her” that night. Mary is supposed to spend the next day packing, but accidentally falls asleep and wakes up in the late afternoon. She suddenly feels compelled to go to the store, and finds Moses in there. She runs away screaming and bumps into Tony, who gently tells her that he has suggested that Dick take her to a doctor.
That night, Mary doesn’t eat supper with Tony and Dick. In bed, Dick tells her that she is ill, and Mary responds that she has always been ill in her heart. After Dick is asleep, Mary gets up and creeps around the house, convinced that Moses is there. She goes out to the veranda, where she sees Moses in the distance. He comes toward her, puts a hand over her mouth, and stabs her to death. Moses briefly considers claiming innocence, before resolving to turn himself in. He waits outside the house until morning.