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.
- Beard of Sorrow: After his wife dies the formerly fresh-faced Apu stops shaving. He has quite the scraggly beard by the end.
- 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.
- Getting Crap Past the Radar: Given the strict censorship of Indian films of the era, the word "pregnant" couldn't be uttered (it couldn't in Hollywood either). So Apu says something about how they'll save expenses because Aparna is going to her parents' house for two months, and Aparna says "What about the extra expenses when we come back?"
- 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."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: "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.