The two main characters are cousins Erasmus Kemp, son of a wealthy merchant from Lancashire and Matthew Paris, a physician and scientist who goes on the voyage.

The narrative interweaves elements of appalling cruelty and horror with extended comedic interludes, and employs frequent period expressions.

Prior to the beginning of the story Paris had been imprisoned for writings on the age of the Earth that clashed with a literal interpretation of the Bible, his wife Ruth dying while he was incarcerated.

Wishing to escape his past, he accepts a position as surgeon on the Liverpool Merchant, a slave ship built and owned by his uncle William Kemp.

He participates in a play initially, and is enamored with seventeen-year-old Sarah Wolpert, the daughter of a friend of his father.

He participates in The Enchanted Island on her suggestion, a rewritten play with characters and dialogue drawn from Shakespeare's The Tempest.

Meanwhile, Kemp's father, a cotton broker, is in financial trouble, relying heavily on strong profits from the voyage of the Merchant.

I have assisted in the suffering inflicted on these innocent people and in doing so joined the ranks of those that degrade the unoffending... We have taken everything from them and only for the sake of profit—that sacred hunger... which justifies everything, sanctifies all purposes.Meanwhile, William Kemp commits suicide owing to fear of his imminent bankruptcy.

Finally, Thurso decides to throw the remaining slaves overboard, the insurance money being more attractive than their prospects for sale in a sickened state.

His wife Margaret is the daughter of a wealthy man, Sir Hugo, President of the West India Association.

The ship's crew and slaves have been living together in a community for over a decade, speaking a trade pidgin from the Guinea coast.

The translator tells the children stories in a pidgin tongue which they all share, while Paris reads to them from Alexander Pope and David Hume.

Erasmus finds Paris' journal among the wreckage of the Merchant, his cousin's writings clashing with his strongly capitalist convictions, and further whetting his appetite for retribution.