Why is the episode involving The Woman introduced through a flashback at this point of the play?
When Bif, Happy and Willy are having lunch after the interview with Oliver
In introducing the occurrence at the hotel room directly after the luncheon, Miller serves to illustrate exactly why Willy's relationship with Biff changed so drastically, thus, allowing us to see one of the reasons Biff's life changed too. In this scene, Miller finally gives a full explanation for Biff's refusal to take a summer school course, the critical event that determined his chain of failures. It is Willy's infidelity that prompted the change in Biff, as he learned that his father was having an affair with the woman in Boston. Yet the revelation of this reason for Biff's bitterness is not the only example in this segment of how Willy has carelessly ruined the lives of those around him. Willy has ruined the reputation of the Woman, but can offer nothing to her in return. Despite the promises that he has made to her, he denies and discards her. This parallels Willy's earlier insistence that Linda should not mend stockings. Stockings serve as a symbol of what Willy can provide and as a measure of his success.
http://www.gradesaver.com/death-of-a-salesman/study-guide/summary-ii6
