Orphanhood
Orphanhood is a symbolic motif in the novel. Susan is given up for adoption because of an unfit mother. While working as an orphan, she is hired by a man who plans on exploiting another orphan, Maud Lily, who is now wealthy. The idea of orphanhood is paired with the question of mental instability, because the man, "Gentleman," is planning to exploit a desperate woman by playing the victim of her emotional instability.
Patriarchy
One doesn't get very far in the novel without realizing that Gentleman is a symbol for the brokenness of patriarchy. Gentleman's name suggests a powerful man who uses his authority to take care of the needy and the oppressed, but this "Gentleman" literally exploits orphans and widows. And, because of his wily nature, he gets other oppressed people to help him by paying them in meager favors and small salaries, using the oppressed as the false enemy of the oppressed.
Maud Lily and Sue
As a character pair, these foils are similar and different. Both have had painful lives full of emotional turmoil, loneliness, exploitation, and disenfranchisement. Both are orphans, and both have damage in their lives caused by mental health crises (Maud is being exploited for alleged hysteria; Sue was removed from her mother for her mother's insanity). The main difference between them is time. This means that they are foils whose dynamic suggests the eternal presence of orphans and widows. By turning them against one another, feminist issues are raised.
Knowledge and power
For Maud, life was a clear-cut game. She lacked power and authority, and the most effective way of gaining power was to gain knowledge. Although Gentleman takes her for a pitiful fool, Maud is passionate about literature and organization. Her character is described by her rich uncle's library, a pleasant condemnation. She feels trapped, but better to be trapped in a library than anywhere else. This is a symbol for her character's chronic desire to learn and grow.
The plot twist
Although Sue wants to kill Maud, she realizes instead that she and Maud were co-victims of a conspiracy. Her real mother is Maud all along, but she was switched at birth and made to be an orphan in an elaborate attempt to exploit the couple of what little they possessed. The desire to kill her mother is therefore an inverse of the Oedipal complex, because without knowing they were related, she desired vengeance against her, like Oedipus and his father.
