Cambridge is the story of two people: Emily Cartwright, the daughter of a slave owner, and Cambridge, one of her family's slaves. The story is narrated by both of these characters. Emily speaks through journal entries of her voyage from England to visit her father’s sugar plantation in the West Indies. She gives her impressions of the plantation and expresses her feelings about it and about the complex dynamics among the people that live there. Emily’s ocean voyage to the Americas is treacherous, and her maid dies during the voyage. However, despite the hardship, she travels as a paying passenger, and thus her voyage is sharply contrasted with the transatlantic voyages of Cambridge, in which he—traveling as a captured slave—endures unimaginable suffering.

Emily’s view of events is tainted by the fact that she has benefitted from her father’s slave owning, but she knows nothing of plantation life. When Emily arrives at the plantation, she finds that her father’s plantation manager has disappeared, and a man named Arnold Brown has taken over. Brown is a brutal slave owner, but nevertheless, he manages to seduce Emily and impregnate her. Brown’s slave mistress, who is mentally unstable, is incensed over this, and Emily begins to fear for her life. Cambridge is this slave woman’s husband, and he is understandably distressed that Brown is using his wife and he can do nothing to stop the abuse. Cambridge also suspects that Brown murdered the former plantation manager. During the course of the story, Arnold is murdered, and Emily gives birth to a stillborn child. Cambridge is hanged for Arnold’s murder. It is on the eve of the hanging that Cambridge gives his account of the events that took place at the plantation, which contrasts with Emily’s account.