In the play Death of a Salesman, infidelity plays an important role in the theme of the play. The definition of infidelity in the play signifies a disloyal act, betrayal and all the lies that were told. We see in the play how this incident was the starting change of the relationship between Biff and Willy. It separates the good times from the bad times. Without infidelity being a major theme, we wouldn't know the reasoning behind the anger and lies that are always told in the play. It was always a mystery to the rest of the characters why Biff and Willy were so angry at each other because they once got along so well. The discovery of the father's infidelity differentiates the before and after of the disloyal act.
The relationship between Willy and Biff at one point was wonderful before Biff discovered his dad's infidelity. Biff loved his dad and looked up to him. Biff demonstrated his love to his dad when he told him, "This Saturday, Pop, this Saturday----just for you, I'm going to break through for a touchdown" (Miller 1680). Willy supported his son's passion for football even though he knew that Biff wasn't doing well in Math. Biff flunked Math and wasn't able to graduate. This was the reason Biff went looking for Willy so his father could persuade his teacher to give him the extra points he needed. Instead of finding his dad alone, he seen the woman that was in the bathroom. Biff was devastated when his father's infidelity was revealed saying, "You---gave her Mama's stockings!" (Miller 1726). This caused Biff to become furious with his father yelling at him, "You fake! You phony little fake! You fake!" (Miller 1726). This is where infidelity played a major role in the play because it informed the audience why Biff was so mad at his father throughout the play. Wille leaves home and didn't attend summer school.
When Biff returns back home he's not the same Biff as before.