Salento, Italy, June 1934: A coach stops in the main square of Lizzanello, a tight-knit village where everyone knows each other. A couple gets off: The man, Carlo, a child of the South, is happy to be back home after a long departure; the woman, Anna--his wife--is a stranger from the North. She is as beautiful as a Greek statue, but dubious. Salento is her husband's hometown, and while it's only logical to him that they move back after inheriting land and house in the wake of an uncle's passing, Anna is unsure of the role she'll have here. What kind of life awaits her?

In a small, muggy town like Lizzanello, there aren't many options for a woman with Anna's sensibilities and ambitions, who doesn't attend church nor gossip. So when she learns that the post office is hiring, she leaps at the opportunity, eager to have a role outside of "mother" and "wife." Taking the postal service exam, and passing with flying colors, Anna proudly dons the navy blue cap and begins delivering letters. While she might not trade rumors, that doesn't stop her from being the subject of conversation. Her sister-in-law is shocked when Anna doesn't serve the men of the house as she's supposed to, her young niece admires her strange new aunt, and her brother-in-law finds himself beguiled by her beauty and intelligence.

Anna worries that she'll never cease to be "the foreigner." But over the next twenty years, as she ferries letters between secret lovers, men at war, and families near and far, Anna will become the invisible thread connecting a community she never expected to fit into.