In between the sea and the plains of Bengal, on the easternmost coast of India, lies an immense archipelago of islands. Some of these islands are vast and some no larger than sandbars; some have lasted through recorded history while others have just washed into being. These are the Sundarbans. The settlers of the Sundarbans believe that anyone without a pure heart who ventures into the watery labyrinth will never return. It is the arrival of Piyali Roy, of Indian parentage but stubbornly American and Kanai Dutt, a sophisticated Delhi businessman, that disturbs the delicate balance of settlement life. Kanai has returned to the islands on the request of his aunt, a local figure, for the first time since the death of his uncle, a political radical who died mysteriously in the aftermath of a local uprising. When Piya, who is on the track of the rare river dolphins, hires Fokir, an illiterate but proud local man to guide her through the backwaters, Kanai becomes her translator. From this moment, the tide begins to turn.