Political schism
Isabel is sold into slavery with her sister to British citizens who have moved to America. These are very uppity people, like what might be called duke and duchess in Europe. In the novel's setting, this home is clearly an elaborate imagery depicting the essential differences between Britain and America. Even though America has its political origin in the order imposed by British monarchy, there is absolutely no denying that America is obviously much different socially and culturally from its mother country.
Conspiracy
Isabel is defined by her insolence (her owner's word for which she brands Isabel on the cheek with an "I"), but actually, Lady Seymour is completely unable to break Isabel because Isabel's "I" can also be seen as a symbol for her essential innocence. She does not deserve to have to submit to an owner, so her insolence is shown to be a good thing. In fact, she uses that insolence as a heroic trait by establishing connections with the rebels and using her insight to conspire against her owner with the American Revolutionary efforts.
Slavery and prison
The imagery of control and domination defines the book because it is also the defining aspect of slavery. As the Americans toil to attain freedom from what they consider to be a tyrannical authority (the British crown, to be specific), they simultaneously provide reasons why slavery should not ever have been tolerated. When Curzon is imprisoned and removed completely from his dignity or any opportunity for freedom or a better fate, that is a symbol for what slavery leads to socio-economically. The imagery is uncanny.
Historical remembrance
An interesting essay could be written about what the novel accomplishes by using historical imagery. The novel is fictional, which is important, because that means that there are aspects of the novel which draw from the reader's understanding of the American Revolution, and those moments are inserted for artistic effect as well as a rhetorical effect. The imagery of historical remembrance should remind the reader that there were always a lot of Black people actively participating in American history, but because of the historical tendency to dehumanize slaves and deny them education, those points of view have been often eliminated from school curricula.
