Warning: Wikipedia contains spoilers
In 1896, newlyweds Roy and Ada Goodnough leave Iowa and settle down in northeastern Colorado under the Homestead Act of 1862. The business of farming is a tough affair in those days, but Roy is a hard-working man who eventually succeeds in tilling the soil and breeding cattle. Ada bears him two children: Edith, who is born in 1897, and Lyman, born two years later. As their neighbour, Hannah Roscoe, the narrator's grandmother, a half-breed whose husband left her and their little son for good, quietly observes the Goodnoughs and also, on Adaīs request, helps deliver Edith and Lyman.
Very soon Ada regrets leaving Iowa for the plains of Colorado. Her husband turns out to be a bully, an angry and violent man without any sense of humour who makes her and their children work very hard on the farm. When she dies in 1914, aged only 42, Edith has to take over all of Adaīs chores and duties ("Your motherīs dead. Youīre the mother now."). Then, in 1915, a terrible accident during harvesttime seals Edithīs fate: Her fatherīs hands get entangled in a machine, and nine of his fingers are chopped off. This severe physical handicap leaves Roy Goodnough all the more cruel and demanding; he considers, and treats, Edith and Lyman as his "self-sired farmhands", bossing them around and taking all decisions himself.
As the two siblings grow up, they desperately start looking for means of escape. But they soon realize that they are stuck on their fatherīs farm, that, as opposed to city kids, they are bound by a rural code of honour and a sense of duty and thus prevented from abandoning the farm and leaving their father alone. For the next 37 years, Edith performs the duties of farmer, housewife and nurse without ever seriously complaining, renouncing her personal freedom and refusing to get involved with men (except for a brief romance with the narratorīs father who, as would be expected, is rejected by her father as a "half-breed bastard"). Lyman, tall, inexperienced in the ways of the world and deeply frustrated, finally sees his chance of escape when, in 1941, the United States is attacked by Japan. In the middle of the night and with the help of the Roscoes, he secretly leaves the farm and goes to the city with the intention of joining the armed forces. But at 42 he is too old to enlist and instead embarks on a tour of the United States which lasts for more than 20 years. All those years, Edith never doubts that one day her brother will return. He does so, too, in the early 1960s, almost ten years after their fatherīs peaceful death at 82.
After a number of good years which Edith and Lyman, now both in their sixties, can enjoy living together in their farm house and doing some travelling in his car, Lymanīs health begins to deteriorate and his personality starts to change and eventually go to pieces. It is again Edith whose sense of duty tells her to look after her brother. Lyman wreaks havoc when, in 1967, he causes a car accident which leads to the narratorīs wife having a miscarriage. In the following years, Edith draws some pleasure from spending afternoons with Rena, the narratorīs daughter, who is born in 1969. But soon it becomes too dangerous for Rena to go to the Goodnoughs on her own, as Lyman, who has regressed to infancy, is prone to unprompted outbursts of violence.
Eventually, on New Year's Eve, 1976, Edith prepares for her only act of rebellion ever. She has Lyman put on his best clothes, cooks a three-course dinner for him, waits for him to fall asleep and then sets fire to their house. Things do not happen according to plan though because the fire is detected too soon and the two old people are evacuated. However, Lyman never recovers from the injuries inflicted by the fire and dies soon afterwards.
In the spring of 1977 Edith Goodnough is still lying in a hospital bed with a policeman stationed outside her room and facing charges of attempted murder. The Roscoes visit every day. Sanders Roscoe is particularly appalled by the journalists from Denver who, having no idea how hard the farming life can be, have started sniffing around and digging up dirt.