Piya, a cetologist (marine mammal specialist), embarks on a river expedition with Fokir, a local fisherman, to study river dolphins. Despite the vast linguistic gap between them—Piya speaks no Bengali, and Fokir speaks no English—they communicate through gestures, expressions, and shared understanding of the water and its creatures.

Their journey becomes a meditation on unspoken connection and the beauty of non-verbal human relationships. Piya is impressed with Fokir’s instinctive knowledge of the river and its fauna, contrasting sharply with the scientific method she is trained in.

Their boat meanders through increasingly remote and dangerous parts of the Sundarbans. As they pass areas teeming with wildlife and steeped in folklore, the duo’s bond strengthens, and Piya begins to rely entirely on Fokir’s guidance.

Meanwhile, Kanai stays at Lusibari and starts reading the long-delayed journal left by his uncle Nirmal. The notebook narrates Nirmal’s ideological transformation and emotional turmoil during the late 1970s, particularly around the events at Morichjhãpi—a real-life massacre where the West Bengal government evicted Bangladeshi refugees who had settled on a protected forest island.

Nirmal’s writings reflect a deep conflict between revolutionary zeal and helplessness in the face of systemic power. He is portrayed as an idealist who struggles with his inaction during a humanitarian crisis. His intense admiration for Kusum—a refugee woman and Fokir’s mother—adds a personal dimension to his political regret.

Through this narrative within a narrative, readers are given insight into the troubled past of the tide country, which mirrors the personal disillusionment of its inhabitants. Kanai, a rational and modern man, finds himself affected by his uncle’s words in ways he didn’t expect.

As Piya and Fokir continue their expedition, a massive cyclone approaches. They are unaware of the full extent of the danger until it's too late. Piya urges Fokir to turn back, but he decides to seek shelter in an ancient shrine to Bon Bibi—the guardian goddess of the Sundarbans.

In the shrine, the myth of Bon Bibi seems to come alive. Bon Bibi, the protector of the forest and its people, represents a spiritual equilibrium between man and nature. Piya, an outsider, feels a momentary sense of awe and peace in this sacred space, despite the encroaching storm.

As the cyclone hits with devastating force, Piya and Fokir battle against nature's fury. Their boat is destroyed, and they cling to the remnants of the structure and to each other. Fokir sacrifices himself trying to shield Piya from debris and water. His death is a deeply emotional moment—he dies silently, as he had lived, without words but with immense meaning.

Kanai, alarmed by the storm and guided by guilt and concern, sets out to find Piya. His physical journey through the flooded and devastated Sundarbans becomes a metaphorical journey into self-awareness and vulnerability.

After locating Piya, he learns about Fokir’s death. He is overwhelmed by Piya’s grief and the realization of her deep connection with Fokir. This humbling experience changes Kanai, who up until this point had been marked by arrogance and detachment. He begins to understand the limits of intellectual superiority and the power of emotional truth.

Kanai leaves Lusibari transformed. He acknowledges the need to let go of control and to recognize the worth of those who live in harmony with nature, unlike himself who has always remained outside it.

Piya returns to Lusibari, broken but determined to honour Fokir’s legacy. She decides to continue her dolphin research, this time in collaboration with Moyna (Fokir’s wife) and others from the local community. This marks a significant evolution in Piya’s journey—from isolated researcher to someone integrated with the community.

Her decision is symbolic: a commitment to inclusiveness, sustainability, and mutual respect. It signals a hopeful future born from tragedy and a deeper understanding of what it means to belong—not through language or blood, but through shared purpose.