Everything you need to understand or teach A Crime of Passion by Mary Higgins Clark.
The plight of the "invisible servant" is the main theme, although there are others. One minor theme is "the woman wronged," an old theme in literature in which a woman who has been mistreated seeks revenge against her oppressors or, instead, shows herself to be truly noble by rising above her suffering. Mark Twain's The Tragedy of Pudd'nhead Wilson (1894) has a fine example of a woman's revenge, whereas Nathaniel Hawthorne's The Scarlet Letter...