A Death in the Family opens with a young boy, Rufus, and his father, Jay, taking a trip to the movie theater together. They enjoy this time spent just between the two of them. On the way home, they stop by a pub so Jay can get a drink. After they return home, Rufus hears his father go out again.

Much later that night, at almost three in the morning, the telephone rings. It is Ralph, Jay's alcoholic brother. Ralph tells Jay that he had better come over soon because their father, Grampa Follet, has had another heart attack. Jay feels that the clearly drunk Ralph may be exaggerating. Nonetheless, Jay feels that he cannot afford to risk it, so he sets off in the Ford early in the morning. After crossing a nearby river on the ferry, he feels that he is driving into his rural "home country."

After Jay leaves, his wife, Mary, has trouble sleeping. She keeps thinking about her basic dislike of Jay's father, and then she begins praying for God to give her strength to like the old man. She also asks God to help Jay become a religious man, as religion is something she and her husband feel differently about. She feels religion is a rift between them in their marriage.

In the morning, Mary tells the children that Jay has gone to see Grampa and that he will be back by nightfall. Meanwhile, Jay has arrived at the farm and is now angry that he made the trip: sure enough, Ralph greatly exaggerated their father's condition. The night before, Ralph kept sneaking out of his father's sickroom to take drinks; he felt he was a failure as a man. He realized that nobody respects him because he is a weak person.

Hannah, Rufus's great-aunt, calls Mary and asks her if she can take Rufus shopping. After Rufus gets home from school, he goes over to his grandmother's house to meet Hannah. The two go shopping together, and the highlight of the trip for Rufus is when Hannah buys him a cap that he desperately wants.

At ten o'clock in the evening of the day that Jay is supposed to return home, Mary receives a phone call from a man who tells her that Jay has been in an accident and that she should send over a male member of the family. Mary immediately calls her brother, Andrew, and he and a family friend named Walter Starr drive out together. Before they leave, they drop off Aunt Hannah so that she can wait with Mary. The two women wait, tense and worried. Mary grows more and more alarmed as time passes.

Joel and Catherine, Mary's parents, are also waiting in their own house. Joel calls Mary to see if she has heard any news, but she has not. Joel is trying to read a magazine to distract him from thinking about what might have happened to Jay, and Catherine is trying to do embroidery.

Then Andrew returns to Mary's house. Mary guesses right away that Jay is dead, and Andrew confirms this fact. Shortly thereafter, Joel and Catherine arrive with Walter, who had gone directly to their house to get them. Joel takes Mary aside and gives her the best advice he can on how to cope with the death. He tells her to stay strong, and that he has confidence in her.

Joel and Mary return to the living room, where Hannah, Catherine, and Andrew are all assembled. Andrew tells them all what happened. He says that a cotter pin fell out of the steering mechanism of Jay's car, and that when he hit a rock in the road he lost control. His head was thrown forward onto the steering wheel, causing a concussion that was instantly fatal and likely painless. He then was thrown clear of the car. They all drink some whiskey.

Andrew calls Ralph to alert Jay's side of the family about the death. Ralph feels terrible, and offers to be the undertaker, but Mary has already brought Jay to a different undertaker. It occurs to Mary that Jay may have been drunk when he crashed the car; she immediately tells herself, however, that Andrew would have told her if that was even a possibility, and she puts the thought out of her head.

Suddenly, Hannah, Mary, Andrew, and Catherine all sense a presence in the room. Mary says that it is Jay. When the presence returns, she feels that it is in the children's room, and she goes upstairs to pray. Even Andrew, who is very skeptical about religion and all things supernatural, is shaken because he is sure he has sensed something. Mary comes downstairs again and asks Hannah to spend the night with her, which the older woman does.

When Rufus wakes up the next morning, the first thing he wants to do is to show his father his new cap. He runs into his parents' room, and his mother tells him to go get little Catherine, his sister, because there is something she has to tell both of them. She tells them that their father has died and that they will never be able to see him again. The children are upset, but do not fully understand the import of the news. At breakfast, Hannah tells them the details of the death and says they can ask her questions about anything.

That day, Rufus wanders around the house aimlessly, unsure of what to do with himself. Even though Hannah tells him to stay in the house, he sneaks out and goes to the sidewalk where kids walk to school. A bunch of them gather around him, and he tells them that his father is dead. One little boy relates the story as he read it in the local newspaper, adding gory details. Another boy says that his father said that Jay was drunk. Then the school bell rings, the boys run off, and Rufus goes home. He gets in an argument with little Catherine over her coloring book, and Aunt Hannah chastises him.

The next day, Hannah washes and dresses Rufus and little Catherine for the funeral. A priest named Father Jackson comes to the house and, after meanly reprimanding the children for staring at him, goes into Mary's room and prays with her and Hannah. The children eavesdrop at the door until Walter Starr arrives. He keeps them company in the sitting room until their mother and aunt emerge with Father Jackson.

The children go to the wake, which is held at their grandparents' house, and see their father for the last time. Back at home, little Catherine feels lonely. She looks for her mother and hides under a bed until Mary finds her. Andrew takes Rufus for a walk. He tells Rufus about a beautiful butterfly that he saw land on their father's coffin during the burial service. The story makes Rufus feel better about not being present at the funeral. Then Andrew gets angry with Father Jackson and tells Rufus that the priest refused to read the full burial service because Jay had never been baptized. As Rufus and Andrew walk home in silence, Rufus wonders if, since Andrew hates religion, he also hates the religious Mary and Hannah.