Oroonoko’s tale is told from the perspective of a female narrator, possibly Aphra Behn herself. The narrator claims to have known Oroonoko during his captivity in Suriname, South America. Suriname is a British colony at the time the narrative takes place (the 1660s). As the novel’s full title announces, Oroonoko is not just any old slave—he is the last descendant of a royal line, and the prince of an African country called Coramantien (probably modern-day Ghana). Coramantien is a brave and warlike nation that participates in the trans-Atlantic slave trade, selling prisoners of war to Western ships.
Oroonoko has grown up away from the court, and has been trained to be a great military leader by Imoinda’s father. One day, during an intense battle, Imoinda’s father takes a fatal arrow in the eye and saves Oroonoko’s life. The seventeen-year-old Oroonoko becomes the new general, and returns to court an elegant and intelligent young man. The narrator spends much time describing Oroonoko’s noble characteristics, and is particularly interested in detailing his exceedingly fine physical beauty, which is a blend of Roman and African traits.
While at court, Oroonoko visits the daughter of his foster father, the beautiful and pure Imoinda. They fall in love at first sight. They participate in a marriage ceremony but Oroonoko still has to ask his grandfather, the King, for his blessing, in keeping with the patriarchal customs of the society. However, the king, a lecherous old man, hears about Imoinda’s beauty. After seeing her at court, he decides he wants her to become one of his concubines. While Oroonoko is off hunting, the king sends her the royal veil, a sign of invitation for attractive women to come to court. Imoinda is duty-bound to obey.
Separated from her true love, Imoinda is kept cloistered at the Otan, the King’s pleasure palace. She is still a virgin and refuses, as much as she can, the King’s advances. Due to the strict laws of the Otan, Oroonoko is prevented from seeing Imoinda until the King invites him.
Despite being persuaded otherwise by those around them, the lovers remain faithful to each other. Oroonoko confirms Imoinda’s longing to return to him from Onahal, one of the King’s old wives, and by exchanging secret glances with Imoinda when visiting the Otan.
Before Oroonoko leaves for war, he is determined to consummate his marriage to Imoinda. With the help of his good friend and fellow warrior, Aboan, he concocts a plan to do so. Aboan seduces Onahal, who quickly agrees to help the lovers, and Oroonoko and Imoinda spend the night together. Unfortunately, the King, who had been suspicious that something might happen, sends his guard to confront Oroonoko, but Oroonoko flees to the battlefront. As punishment for her perfidy, the King sells Imoinda into slavery, an ignoble punishment, but he tells Oroonoko he has executed her.
Upon hearing this, Oroonoko gives up his will to live and fight, and he abandons his troops, retiring to his tent. When they are about to lose, however, Oroonoko rouses himself from his lovesick stupor and leads his army to victory.
An English sea captain comes to Coramantien, and Oroonoko receives him as a royal guest. The Captain double-crosses Oroonoko, however, inviting him onboard his ship and then kidnapping him, along with a hundred of Oroonoko’s attendants. The Captain brings Oroonoko across the Atlantic to Suriname, where he sells him to an intelligent and kind-hearted slave-owner named Trefry. Trefry gives Oroonoko the name “Caesar,” and promises to help free him one day. Trefry also unwittingly reunites Caesar with Imoinda, whom Trefry knows as “Clemene.” Together at last, though in undesirable circumstances, “Caesar” and “Clemene” conceive a child and spend their days mingling with the white nobility, who immediately accept the couple because they are noble, virtuous, and beautiful.
As Imoinda’s pregnancy develops, Caesar becomes increasingly restless and wants to take his new family back home. Though he esteems some white people, like Trefry and the narrator, he is also rightly suspicious of the lengthy delay regarding his release. He feels that he will once again be tricked and his family will remain in slavery. Indeed, this is exactly the plan of Deputy Governor Byam, who is part of the colonial government in Suriname and intends to keep Caesar a slave.
Because he is a man of action, Caesar determines to take matters into his own hands and convince the slaves to run away. Led by Caesar, they manage to escape, but their journey ends in disaster when the white colonists come after them. With the exception of Caesar’s friend Tuscan, most of the slaves flee the group, leaving Caesar and a heavily pregnant Imoinda to confront the plantation owners. They all fight bravely and Imoinda wounds Byam in the shoulder with a poisoned arrow.
With the help of Trefry, Byam convinces Caesar to surrender peacefully and promises to fulfill all his demands. They write a contract, but Byam almost immediately breaks it. He sequesters Imoinda and brutally whips Tuscan and Caesar. Now that he is fully awakened to Byam’s treachery, Caesar vows revenge. He murders Imoinda and their child, with Imoinda’s permission and blessing, to save them from prolonged suffering. Caesar then fails to enact his revenge against Byam, however, when he succumbs to a debilitating grief beside his wife’s corpse.
When the colonists come looking for Caesar, he is rescued against his will by his friends. Sick and dying, he tells them of his plan to kill Byam. They try to encourage him to abandon this idea and focus on recovery. One day, the ruthless Irishman Banister kidnaps Caesar at Byam’s behest. Caesar is again tied to the stake, where he is slowly dismembered, dying without making a sound.