Amitav Ghosh has spent more than ten years writing the Ibis trilogy, his fictional account of the turbulent years leading to the First Opium War of 1839–42. Flood of Fire follows Sea of Poppies (2008) and River of Smoke (2011). It is unnecessary to have read the earlier books, though reuniting with some of the characters is enjoyable.

The novel begins with the grand spectacle of the East India Company Army on the march in remote Assam, 600 sepoys of the Bengal Native Infantry and 2,000 camp followers (who actually lead rather than follow). Havildar Kesri Singh, the senior Indian NCO, enjoys a good relationship with his battalion's adjutant, Captain Mee, whose bad temper he seems to understand. Mee is appointed to command a company of sepoy volunteers in an expeditionary force overseas, and Kesri will accompany him. Descriptions of the sepoys' existence provide a sharp contrast to British life in India. Caste is a concept always present in novels of this period, but its manifestation is almost more striking within the British community, civil and military.