In Act II, Kate Keller is the catalyst that starts the unraveling of the Keller family. When George Deever arrives, he is determined to find a way to get Joe Keller to confess his guilt in the crime that has imprisoned his father. Kate is very agitated about George's visit, she warns her husband, Joe to be smart, to not say anything to provoke George.
Joe acts very casual with George, he even offers to help him settle in his old town. Joe offers to help George get a job, he tells him that he even wants him to convey to Steve that he can have a job when he gets out of prison. Joe is very sanctimonious about the whole matter.
However, Kate ends up revealing something about Joe's health that convinces George that he has lied about his father's singular guilt in the crime of shipping faulty airplane parts to the military.
Kate, contrary to Joe's claim that he had the flu when the faulty parts were shipped, states that Joe has never been sick a day in his life. George jumps on this, recognizing the opportunity that he has been given to unravel Joe's story.
"Joe’s claim that a bout of pneumonia took him away from the plant on the day of the infamous shipment is contradicted by Kate’s assertion that her husband hasn’t been sick for the past fifteen years. It is obvious that Kate should remember something as serious as pneumonia (which Joe changes to the flu during the argument), and the efforts of the two to cover the blunder are unconvincing."