All My Sons is an American tragic play about two families, the Kellers and the Deevers. Joe Keller and Steve Deever knowingly shipped damaged aircraft cylinder heads during World War II, but only Steve is serving for the crime. Ann Deever and Chris Keller are in love, although Ann was originally with Larry, Chris' brother. Larry and Chris' mother, Kate, refuses to believe Larry is dead, though Ann knows otherwise. During the play, Joe is forced to admit that he is guilty and decides to take responsibility for his actions.
In August 1946, Joe Keller, a self-made businessman, and his wife Kate are visited by a neighbor, Frank. At Kate's request, Frank is trying to figure out the horoscope of the Kellers' missing son Larry, who disappeared three years earlier. While Kate still believes Larry is coming back, the Kellers' other son, Chris, believes differently. Furthermore, Chris wishes to propose to Ann Deever, who was Larry's girlfriend at the time he went missing and who has been corresponding with Chris for two years. Joe and Kate react to this news with shock but are interrupted by Bert, the boy next door. In a game, Bert brings up the word "jail", making Kate react sharply. When Ann arrives, it is revealed that her father, Steve Deever, is in prison for selling cracked cylinder heads to the Air Force, causing the deaths of twenty one pilots in plane crashes. Joe was his partner but was exonerated of the crime. Ann admits that neither she nor her brother keep in touch with their father any more and wonders aloud whether a faulty engine was responsible for Larry's death. After a heated argument, Chris breaks in and later proposes to Ann, who accepts. Chris also reveals that, while leading a company, he lost all his men and is experiencing survivor's guilt. Meanwhile, Joe receives a phone call from George, Ann's brother, who is coming there to settle something.
Although Chris and Ann have become engaged, Chris avoids telling his mother. Their next door neighbor Sue emerges, revealing that everyone on the block thinks Joe is equally guilty of the crime of supplying faulty aircraft engines. Shortly afterwards, George Deever arrives and reveals that he has just visited the prison to see his father Steve. The latter has confirmed that Joe told him to cover up the cracked cylinders and to send them out. George insists his sister Ann will not marry Chris Keller, son of the man who destroyed the Deevers. Joe Keller and the rest of his family deny this. However, although Joe's story is that, on the fateful day of dispatch, the flu laid him up, Kate reveals that Joe hasn't been sick in fifteen years. George then redoubles his attacks. Joe also seeks to defend himself by explaining that he was building a business for his sons. Chris has never accepted this and remains furious with his father. Meanwhile, Frank announces his horoscope, implying that Larry is alive, which is just what Kate wants to hear.
Chris has gone missing. Reluctantly accepting the ubiquitous accusations, Kate says that, should Chris return, Joe must express willingness to go to prison in hopes that Chris will relent. As he only sought to make money at the insistence of his family, Joe is adamant that their relationship is above the law. Soon after, Ann emerges and expresses intent to leave with Chris regardless of Kate's disdain. When Kate angrily refuses again, Ann reveals to Kate a letter from Larry. She hadn't wanted to share it, but knows that Kate must face reality. Chris returns, and is torn about whether to bring Joe in himself, knowing it doesn't erase the death of his fellow soldiers or absolve the world of its natural merciless state. When Joe returns and refutes his guilt on account of his life's accomplishments, his son wearily responds, "I know you're no worse than other men, but I thought you were better. I never saw you as a man...I saw you as my father." Finally, the letter, read by Chris, reveals that because of his father's guilt, Larry planned to commit suicide. With this final blow, Joe finally agrees to turn himself in, goes inside to get his coat but then kills himself with a gunshot. At the end, when Chris expresses remorse in spite of his resolve, Kate tells him to not blame himself and to live onward.