Ann’s father, Steve Deever, is in prison for knowingly shipping defective aircraft parts during the war, which caused the deaths of twenty-one American pilots. Joe Keller, Steve’s former business partner, was acquitted because he claimed that he had been ill and absent when the parts were shipped. Chris proposes to Ann, and she accepts, but their plans are complicated when Ann’s brother, George, calls to announce that he is coming to visit. The act establishes the conflict between family loyalty, personal happiness, and moral responsibility.

George arrives after visiting his father in prison. He explains that Steve claimed Joe had instructed him to repair the cracked cylinder heads and paint over the damage before shipping them. George believes Joe deliberately escaped punishment and refuses to allow Ann to marry Chris. Joe attempts to defend himself, but Kate accidentally reveals that he has not been ill for many years, undermining his original alibi. Under pressure, Joe admits that he knew about the defective parts and allowed them to be shipped because he feared losing his business. Chris is devastated because he has always admired his father and believed him to be an honourable man.

Ann reveals that she has a letter written by Larry before his death. In the letter, Larry explains that he intends to take his own life because he cannot bear the shame of his father’s involvement in the deaths of the pilots. The letter confirms that Larry died by suicide, forcing Kate to confront the truth she has denied throughout the play. Joe finally understands the consequences of his actions: his decision to protect his business contributed to the deaths of twenty-one pilots and destroyed his own family. He goes inside and shoots himself. The play ends with Kate urging Chris to live his life, leaving him to face the painful consequences of his father’s actions.