Being Versus Seeming
Another way of putting this theme is that it is all about how appearances can be deceiving. Many of the characters seem to be one thing but are ultimately revealed as actually being something else, very often the opposite of their façade. The title character’s contextual background situates her necessity for seeking a job on the lower end of the economic spectrum in such a way that one at first senses she is something a bit more complex than she seems to her employers. The husband and wife who employ Millie for domestic help do not just simply wind up being different than they seem but even within the façade they present to Millie there are questions about what is the real person and what is the false persona.
Domestic Abuse
The theme of things seeming to be one thing but turning out to be something different is engaged to explore another theme. The story subverts several expectations related to the issue of domestic abuse. The traditional role of domestic help in fiction is often that of objective witness to the worst aspects of their employers while remaining safely outside the fray. This trope is subverted by the housemaid being purposely drawn into the situation in a way that winds up giving domestic abuse an entirely different connotation. The question of how to end such abuse when issues of gender inequality and class division come under scrutiny and into play is explored as the narrative works its way through the revelations of who is seeming to be something they are not and for what reason.
Vengeance
That narrative thread winds its way around revelations that stimulate justification for revenge. The issue of hiding the real self while seeming to be something different is incorporated into those justifications for evening scores. Events of the past gradually unfold to demonstrate how the positions of each major character at this point in time is just one level of a complicated layering of existence. Acts have consequences which are sometimes positive and sometimes negative in the short term within each layer. These consequences then produce the acts within another layer that turn the negative into positive and vice versa. At some level for each of the main characters, the urge for revenge becomes a dominating force in moving them to actions which create further complications in their consequences. Ultimately, the story is revealed to be powered entirely by the fuel of the desire to extract revenge.
