Khandwa Village, 1986. A young boy, Saroo, stands in a clearing in central India, surrounded by a swarm of butterflies. His older brother, Guddu, calls to him, and they go to jump onto a coal train. When an officer yells at the boys and begins running alongside the train to catch them, they yell in defiance.
Saroo and Guddu jump off the train and go to the river, as Guddu praises his brother for jumping from such a height off of the train. At the market, Saroo wants a jalebi and they dream about buying all of the sweets. At home, they bring milk and money to their mother, Kamla, who asks where they got the items. Also present is their younger sister, Shekila.
As Kamla prepares to leave for her job collecting rocks, she asks Saroo to look after Shekila. The next day, Guddu prepares to go away for a week to lift bales of hay for money, and Saroo wants to go along. Guddu reminds him that he is meant to stay with their sister, Shekila. Saroo desperately wants to come, lifting up a chair and a bicycle to prove that he can lift bales of hay, and Guddu finally agrees to let him come along.
They ride a bicycle through the village and sneak onto a train, riding it through the night. When they arrive at a station, Saroo is asleep and does not want to keep going, which causes Guddu to regret bringing him. As Saroo sleeps on a bench, Guddu tells him to wait there and he will come back and fetch him. Saroo watches Guddu go, and tells him to bring back 100 jalebis, then changing it to 2,000.
When Saroo awakens, the train platform is completely empty. He wanders towards a nearby train car, calling for Guddu, and climbs aboard, eventually falling asleep. When he awakens, the train is rumbling down the tracks, but there is still no one aboard. The doors are locked and Saroo begins to panic, yelling for his brother.
Time passes, and Saroo stays on the train. We see him calling out to his mother and brother, telling them that he misses them. As the train stops somewhere isolated, Saroo calls to a young girl sitting in the sand outside, and asks her to help free him. She just stares at him, as the train continues.
A supertitle tells us that the train ends up in Calcutta, West Bengal, which is 1600 kilometers east of Khandwa. Saroo arrives at a crowded train platform and jumps off as an officer opens the door. He calls for Guddu and his mother, then tries to tell people where he is from as they rush past. "Ganestalay?" he says to people, but they push him aside and send him away at the ticket booth.
The film centers on the experience of a young Indian boy, Saroo, who has a loving and close relationship with his family as they struggle with the indignities and hardship of poverty. The first image of the film is a beautiful one: Saroo standing in the middle of a swarm of butterflies, outstretching his arms to them, almost as though suspended in time and space. Soon enough, he is jolted out of this reverie by his beloved older brother, Guddu, who coaxes him to jump onto a passing coal train. Soon after that, they steal some essential items from a market to bring home to their mother.
Saroo is especially close to his older brother, Guddu, who encourages him and shows him a great deal of love. They are nearly inseparable, and when Guddu prepares to go away to lift bales of hay for money, Saroo wants to accompany him, even though he is very young and has been charged with looking after their younger sister, Shekila. Guddu eventually agrees, bringing the eager Saroo along. Their bond is so close that even though Saroo is so young and unequipped for the manual labor, Guddu wants to have him with him.
Saroo's insistence that he is up to the trip soon proves inaccurate, however. About midway through the journey, he becomes extremely tired, and is unable to go forward, lying down on a bench on the train platform. Guddu insists that he will be back for his brother soon, but when Saroo awakens, he finds the platform abandoned and accidentally winds up on a train to who-knows-where. What had seemed like a harmless plan built around fraternal loyalty soon becomes a tale of disconnection and loss, as Saroo finds himself out in the world, completely alone.
The film is beautifully and delicately shot, in such a way that amplifies the drama and heartache of the family separation. Director Garth Davis films the young Saroo as he wanders around the empty train platform and then the empty car with an easy pace and quiet attention, as golden light streams in through the windows. Hauschka and Dustin O'Halloran's score, made up mostly of plaintive strings and piano lines, also illuminates the drama of the narrative, and puts the viewer in mind of the melancholy of separation and Saroo's fear.
At the other end of Saroo's isolated journey on the train is a bustling and intimidating city, Calcutta. When the doors of his train finally open, it spits the young Saroo out into a city that is thrumming with activity and the unknown. He calls out for his brother, standing on a ledge above a giant sea of people, slowly realizing that he is alone. It is thus that the conflict of the film—a desire for a seemingly impossible family reunion—is set into motion. The young Saroo must forge his own path, without anyone to look after or help him.