I think the most important incident in the play is when Maggie decides that she is going to marry Willie. There are several reasons why this incident is so important. Primarily the relationship between Maggie and Willie develops and has effects upon both Maggie's sisters, her father and each of them. It adds excitement to the play because, in this era, women were not supposed to be so strong willed and were expected to do as they were told. Maggie is a very clever women and manipulates men, especially her father, extremely well it was at the start of the twentieth century that women like Maggie were beginning to think they should be able to make their own choices about marriage and being an equal partner in a marriage rather than a dutiful and obedient wife.
Maggie surprises Willie by proposing to him and then has to "get rid of" Willies girlfriend Ada Figgins who is very quiet and gives up Willie far too easily.
Maggie can see that her choices are very limited and decides to take the best option by proposing to Willie. She realises with his skill and her intellectual ability they would make a good team. However Maggie does not forget her sisters and devises a brilliant plan to allow them to marry their partners of choice.
Because of Maggie's plotting she and her sisters are released from their father's shop where they worked for no wage, Maggie's subsequent marriage to Willie works out well for all concerned. Willie is quiet happy being subservient to his wife and is even greatly appreciative of her raising his station in life.
The whole idea of this would be quiet shocking to the audience who would find it difficult to accept the idea...