The film opens with Apu, now a young man, in Calcutta in the 1930s. He is alone in the world after the deaths of his mother and father in Aparajito. Apu is not only alone but dead broke, forced to drop out of school after his mother's death leaves him unable to afford his tuition, unable to even pay the rent on his shabby little boarding house room. He is struggling to make it as a writer when an old school friend invites him to come attend a wedding in the countryside. This spur-of-the-moment casual decision leads to major changes in Apu's life.
Based on the last two-thirds of the novel Aparajito, the previous film in the trilogy having been based on the first third of that novel as well as the end of the Pather Panchali novel. Ravi Shankar provided the music, as he did for the other films in the trilogy.
- Arranged Marriage: As so often in Indian society, Aparna is not marrying for love, but because her father, Sasinarayan, has arranged it. She barely knows Binu, her fiancé, but custom dictates that she must marry by the end of the day, or she will be considered unfit for marriage. Unfortunately, by the time he arrives at Aparna's house, Binu has gone mad from the heat,note causing Aparna's mother to veto the marriage. Pulu hastily recruits the single Apu as a replacement bridegroom.
- Beard of Sorrow: After his wife dies, the formerly fresh-faced Apu stops shaving. He has quite the scraggly beard by the end.
- Bearer of Bad News: Apu returns home from work, having spent the journey reading a letter from Aparna reminding him that he promised to come to her family's house during a religious festival, and finds Aparna's brother Murari waiting outside his flat. The distraught Murari can barely choke out the words "Aparna... in childbirth..." Apu is so overwhelmed by grief that he punches Murari to the ground and locks himself in his flat.
- Blowing Smoke Rings: While Pulu and Apu are in the diner talking about the wedding trip, a man in the background can be seen making some very well-formed smoke rings.
- Coming-of-Age Story: Completes Apu's arc, as he evolves from a callow youth to a husband and father.
- Death by Childbirth: No doubt common enough in India under The Raj. Aparna dies giving birth to her and Apu's son Kamal.
- It's All Junk: A despairing Apu throws away the manuscript of his novel after Aparna dies.
- Leaning on the Fourth Wall: When Apu talks about the novel he wants to write about his own life, emphasized with a cameo from Pather Panchali's theme."Through his education and struggles, we watch as he sheds his old superstitions and fixed views."
- Marriage Before Romance: Apu is jittery at first after being coaxed into marrying a woman he literally just met, and Aparna for her part breaks down sobbing when she gets her first look at Apu's shabby little one-room apartment. But they wind up falling deeply in love.
- Maternal Death? Blame the Child!: When Pulu asks Apu why he has refused to even visit his son Kajal, who is being raised by Aparna's family, since he was born, Apu replies, "It's because Kajal is alive that Aparna isn't."
- Most Writers Are Writers: Apu is trying and mostly failing to scratch out a living as an author. Part of the reason he's struggling so badly is that he rejects jobs as a manual laborer and a clerk as being beneath him.
- Time Skip: The ending skips five years to find Apu's infant son now a mischievous child in Aparna's family's household.
- Train-Station Goodbye: Apu bids Aparna goodbye as she goes home to deliver the baby, complete with standard jog-after-the-train farewells as she reminds him of some errands to run.
- Untranslated Title: The World of Apu (and some sources refer to the film by this title).
- Uptown Girl: Aparna, Apu's bride, is from a very wealthy family. Both she and her family are happy with Apu, but he is acutely aware of his poverty.
- Write Who You Know: In-Universe. Apu, who is struggling to establish himself as a writer, hits on the idea of writing a novel about his own life.
- Walking the Earth: Apu spends five years wandering aimlessly as an itinerant laborer after his wife dies.