The disappearance of her old friend, Lila Cerrullo, causes 60-year-old author Elena Greco to reflect on the early days of their friendship in 1950s Naples, when Elena and Lila are two very different girls at the top of their class. When the girls discover the lair of Don Achille, a criminal figure who controls the neighborhood, they decide to confront him.

As fourth grade draws to an end, Elena and Lila fight with their families for the chance to continue their education. Later, a trip out of town becomes a day Elena will never forget, and a death changes things in the neighborhood forever.

Now a teenager, Elena grapples with the onset of puberty, her studies, and her friendship with Lila, who now works in her family's shoe-repair store. After a library awards ceremony reveals what Lila has been keeping secret, Elena learns what her friend's grand plans might be. Lila takes a stand against the dangerous Solara brothers.

Elena returns to Naples to find Lila has made a romantic connection with Stefano, despite the looming presence of Marcello. As Lila embraces a more glamorous life at Stefano's side, Elena warns her about what people are saying around the neighborhood. Later, in hopes of keeping up with her friend, Elena encourages one suitor and rebuffs the advances of another.

With sales of Cerullo shoes lagging, Stefano cuts a business deal with the Solaras against Lila's wishes. After Elena gets kicked out of a class for voicing her opinion, Nino encourages her to write an article for his magazine about her experience. Later, Elena and Lila get unwelcome surprises.

With Lila on her honeymoon on the Amalfi Coast, Elena struggles to handle school and her relationship with Antonio. When Lila returns with visible bruises on her body, the two girls revert to their natural closeness and Lila’s will to take revenge against her husband grows. Elena continues to be bewitched by Nino Sarratore’s charisma but chooses not to mention him to Lila.

Elena's relationship is threatened when Antonio discovers she has asked the Solaras' help to keep him from doing military service, while Lila remains rebellious in her marriage to the often-violent Stefano. After a photo of her is exhibited at a wedding dress shop in the center of town and becomes the subject of much gossip, Lila makes a bet with Elena about how the whole affair will end.

After Nino's unexpected appearance at her book presentation in Milan, Elena realizes her childhood crush never really abandoned her, and doubts begin to form about her fiance Pietro. Later, a scathing review leaves Elena questioning herself as a writer.

Concerned about Lila's worsening health, Elena seeks advice from her future mother-in-law Adele, who encourages her to write an expose on the Soccavo plant and the mounting unrest between rival unions. After several doctors' visits, Lila becomes determined to move back to the neighborhood despite being viewed as a pariah.