“Flood of Fire” is a novel by the Indian writer Amitav Ghosh, the second part of a trilogy that also includes “Sea of Poppies” and “River of Smoke.” The work immerses the reader in the historical context of the 19th-century Opium Wars, narrating the fates of people of various nationalities and social strata whose lives became intertwined with the opium trade between India and China.