The main characters include Deeti, an ordinary village woman, an "octoroon" American sailor named Zachary Reid, an Indian rajah / zamindar called Neel Rattan Halder, and Benjamin Burnham, an evangelist opium trader.

The novel interweaves the stories of a number of characters, who all, in the latter half of the novel, find themselves taking passage from Calcutta to Mauritius on a schooner named the Ibis.

Deeti looks almost certain to meet her doom when she is forced to consider sati ritual (immolation on her husband's funeral pyre) as the only option in the face of threats of more rapes by the brother-in-law, but then Kalua, the untouchable caste ox man from the neighbouring village, comes to her rescue.

Neel Rattan Halder, a wealthy and unworldly rajah whose dynasty has been ruling the zemindary of Raskhali for centuries, is confronted by Mr. Burnham with the need to sell off his estates in order to pay for the debt he had incurred when investing in the opium trade with China.

In prison he meets Ah Fatt, a half-Chinese, half-Parsi opium addict from Canton, and the two are put aboard the Ibis.

Her father was a politically radical botanist, her mother died in childbirth, and her grandparents were the historically inspired Jeanne and Philippe Commerson.

Paulette feels more at ease with Indian manners, food, and clothing than with Western ones, but the Burnham household fiercely disapproves.

Paulette becomes determined to run away because of sexual harassment by Mr. Burnham and pressure to marry his friend, the stern, elderly Justice Kendalbushe.

Numerous plot developments are facilitated by Nob Kissin Baboo, a Vaishnavite would-be priest who is working as an overseer for Mr. Burnham and comes to believe that Zachary is an avatar of Krishna.

The novel closes with Neel, Ah Fatt, Jodu, Serang Ali and Kalua escaping in a longboat towards Singapore, while Deeti, Paulette, and Zachary proceed towards Mauritius.