The night Ann Deever returns to her old neighborhood to visit Chris Keller and his family, a tree in their backyard blows over in a storm. The tree was planted as a memorial to the older Keller son, Larry, a fighter pilot who was lost in World War II. The morning after the storm, family members and neighbors gather in the yard to chat, to read the newspaper, and to discuss Ann’s return.
Ann’s father, who was Joe Keller’s partner in a wartime business, is in the penitentiary for having allowed cracked cylinder heads to be shipped, which caused the deaths of twenty-one pilots. (Joe was jailed, too, but was later exonerated for his part in the incident.) After the neighbors leave and while Ann is still inside the Keller house eating breakfast, Joe and Chris—a father and grown son who obviously admire each other—discuss Larry’s tree falling and the effect it will have on Kate, the mother. Chris also tells his father that he asked Ann to visit because he wants to ask her to marry him; Joe responds that his mother will not like the news because she still thinks of Ann as Larry’s girl. Chris explains that if he is to stay with the family business, he will need his father’s support in convincing Kate that Larry is not coming back from the war and that Ann and he have the right to be happy.
When she enters the backyard, Kate tries to downplay the significance of Larry’s destroyed tree, but she notes the coincidence of Ann’s return. She reminds the two men that she is sure Larry is not dead and that Ann must share that sentiment. Chris tries to reason with her, but she insists that it is possible that Larry is still alive. She mentions that a neighbor is working out Larry’s horoscope to establish whether or not Larry’s plane crash could have occurred on one of Larry’s “lucky” days.
Once Ann joins the Keller family in the yard, the talk turns to old times and ultimately to Larry. Ann makes it clear that she is not waiting for Larry, but Kate tells her that she should listen to her heart, “because certain things have to be, and certain things can never be.” Their talk also turns to Ann’s father in prison, and Ann reveals that her sympathy for him came to an end once she heard of Larry’s crash. Joe explains that Steve—Ann’s father—is not a bad man, just the type of weak man who buckles under pressure. Joe goes on to say that in spite of Steve’s claim that he, Joe, approved the damaged shipment, he would be willing to let Steve come back to the business, not as a partner but as a worker. Ann marvels at Joe’s magnanimity, and Chris agrees that he is “a great guy.”
After the group makes plans to go out for a celebratory dinner, Chris and Ann talk seriously. Chris explains his feelings for her, and Ann assures him that she wants to marry him. Chris also confides his guilt in having survived the war, explaining that in combat he realized his responsibility for others. He wonders whether there is any meaning to all the suffering and destruction and whether his actions and participation in his father’s business since the war are admirable or self-serving.
Ann’s brother George calls after having visited their father in prison, and he announces that he needs to see the Kellers. He does not say why, and Joe begins to worry that he might want to stir up old trouble. In anticipation of George’s return, Kate makes his favorite grape drink and tells her husband: “Be smart now, Joe. The boy is coming. Be smart.”
Ann challenges Chris’s complete acceptance of his father’s innocence, and Chris asks: “Do you think I could forgive him if he’d done that thing?” Later that afternoon, George arrives. He tells Chris and Ann that his father charged Joe with having given him the go-ahead to ship the defective cylinder heads and with lying about his role in the crime when he claimed to have been home, sick in bed.
Chris and Ann are able to calm George, and once Kate greets him and reminds him of all the good times in the old neighborhood, George accepts the Kellers’ dinner invitation. Joe appears in the backyard and greets George, and eventually the conversation turns to Joe’s remarkable good health. Kate offhandedly mentions that he has not been sick a day in his life. Joe interjects with a reminder that he had the flu during the war, but George catches the Kellers in the discrepancy and he openly charges Joe with having let his father take the blame.
George storms out, and Chris confronts Joe, asking him what he did with the 120 cracked engine heads. Joe explains that a slowdown in production would have been costly for the business and that he let the shipment go, but he did not think that the defective parts would be installed. He concludes by saying that he did it for Chris. Chris yells back at him and pounds on his father’s chest before he leaves.
At two o’clock the following morning, Kate and Joe discuss the situation and wonder what their son will do with their secret. Ann enters the backyard where they sit and says that she will do nothing about Joe but that Kate must accept that Larry is dead so that she and Chris can marry. Kate balks and Joe goes into the house. Ann produces a letter from Larry written on the day he crashed, in which he tells of knowing about his father’s part in the shipment of defective engine parts and that it is his intention to crash his plane.
When Chris returns, he announces that he is going to leave home and asks his parents what they are going to do to make the situation right. Joe, still unable to comprehend, asks why he is considered “bad,” to which Chris responds, “you’re no worse than most men but I thought you were better. I never saw you as a man. I saw you as my father.”
Chris reads Larry’s letter aloud to his father and asks him if he understands his moral obligation. Just before going back into the house, Joe haltingly admits that the deaths of the twenty-one pilots are his responsibility: “they were all my sons.” A few minutes later, inside the house, Joe shoots himself.