The film opens with a train accident whose impact will gradually unfold. Ashima, portrayed by Tabu, is a young Bengali girl skilled in classical singing, who finds herself in an arranged marriage with Ashoke Ganguli, played by Irrfan Khan, a Bengali man settled in New York. After leaving her homeland and family behind, Ashima strives to adapt to the fast-paced lifestyle of New York, grappling with the challenges of cultural differences, harsh weather, and a cramped apartment where she feels isolated from her neighbors. As Ashoke dedicates his time to studying and working long hours, Ashima frequently battles loneliness.
Despite their struggles, the couple gradually grows closer, although expressing emotions proves difficult due to their upbringing, which encourages restraint between men and women. Eventually, Ashima gives birth to a son, whom Ashoke names Gogol, in homage to the Russian author he admires, although in accordance with Bengali tradition, the boy receives the "good name" of Nikil, which is lovingly shortened to Nicky by his American friends. Later, they welcome a daughter named Sonia, who, as a teenager, portrayed by Shahira Nair, embodies a rebellious spirit that clashes with the traditional expectations placed upon her by her family, including her grandparents—Ruma Guha Thakurta, Tanushree Shankar, Sabyasachi Chakraborty, and Tamal Ray Chowdhury—who pressure her to settle down, marry, and start a family. Sonia yearns for independence and chooses to relocate to California to carve out her own path.
As Gogol, acted by Kal Penn, grows up, he navigates the complexities of American adolescence, spurred by a family trip to the Taj Mahal, which ignites his passion for architecture. His relationship with Maxine Ratliff, an all-American girl portrayed by Jacinda Barrett, sends him spiraling away from his own familial ties. When Ashoke travels to Ohio for teaching, he unexpectedly suffers a fatal heart attack, thrusting Gogol into a deep confrontation with his cultural identity and grief. Struggling to allow Maxine to comfort him, the strain ultimately causes their relationship to dissolve.
Recalling his father's harrowing tale of survival during the train accident, Gogol is reminded of the fragility of life. Later, he reconnects with Moushumi Mazundar, played by Zuleikha Robinson, a fellow Bengali who has embraced Western culture and independence. Although their parents once envisioned a marriage between them, Gogol initially perceives Moushumi as meek and conventional. Yet, she transforms into a confident businesswoman and they marry, sharing an intense connection. However, their marriage falters as Moushumi's sociable nature clashes with Gogol's preferences and culminates in an affair with an ex-boyfriend, pushing Gogol towards self-acceptance regarding his cultural roots.
Meanwhile, Ashima contemplates returning to India, feeling disconnected from a country she never fully understood. Though she offers to cancel her upcoming trip, Gogol encourages her to go, relishing his newfound sense of freedom during this pivotal phase in both their lives.
