Slavery and entrapment are themes woven throughout this novel and exist in a complex relationship to one another. Rhys makes the point that the trauma of slavery does not end with the Jamaican Emancipation Act that frees the slaves early in the novel. She also demonstrates that the trauma of slavery harms both blacks and whites, both former slaves and those were always "free." Entrapment is a part of this: the owners were almost as entrapped by the system of slavery as slaves, and systems of entrapment continue to pulse outward long after slavery has died.

Antoinette is a child when the Emancipation Act passes, and the Cosway estate she lives on, Coulibri, quickly goes to rack and ruin when most of the slaves flee on being freed. She, her mother, and her brother are impoverished. They cannot cope on their own and yet the legacy of the Cosway family as "wicked and detestable slave owners," as Daniel calls them, means they can get no help.

This leads to madness for Antoinette's mother and to another form of entrapment for Antoinette: she is married to Rochester, an Englishmen whose family wants him to have her fortune. Her family makes no provision for her to have an income or any control of her money, trapping her in Rochester's hands. Further, the legacy of slave continues to haunt her as the vengeful Daniel Cosway, a former slave who insists he is the son her father, poisons Rochester against her in revenge for wrongs he feels he has suffered.

Even England does not save Antoinette, now called Bertha, from entrapment, for Rochester decides she is mad—and thus drives her to madness. Systems that put disproportionate amounts of power into one set of hands, Rhys shows, be they slaveowners or patriarchs, continue a cycle of suffering and trauma across generations.

The idea of slavery and entrapment in Wide Sargasso Sea is through the novel - beginning with the title. The Sargasso Sea is an almost lifeless area located between the Caribbean and Europe where there are no ocean currents and often there is a complete lack of wind - causing ships to become trapped. It is symbolic of Antoinette being trapped lifeless, suspended between the two worlds.

The Cosway family were former slave owners, their poverty make them outcasts from the white Jamaicans, and the former slaves have either run away or despise the family. Their poverty and the death of their horse isolates and traps them at Coulibri. Antoinette seeking to find a place repeatedly reaches out for love, but ultimately is always rejected and faces isolation both figurately and literally, culminating in her being locked away and trapped in the attic.

Rochester feels isolated by his feelings of being 'exiled' from England and trapped in the situation once he is married to Antionette. His marriage to her was for financial reasons, and as he begins to doubt her he wonders if he has sold his soul to fulfill his family's ambitions.

The character's social positions make them slaves to other's wishes. Both Antoinette and Rochester must marry because of their families, which creates a feeling of entrapment for both. The idea of slavery is destructive from the beginning of the novel, with the burning down of Coulibri by the former slaves. Entrapment runs throughout the novel through the isolation the characters feel.