Cora Gibbs is an illiterate woman lives on a farm with her husband Tom. She has never really seen the world and knows very few people beyond her family and her neighbor, Mrs. Brabbam.
One day, her nephew Benjy comes to stay with her. Cora notices that Benjy can both read and write. She decides that she will start writing letters to people. She gets Benjy's help to write them. Unfortunately she doesn't know many people. At the suggestion of Benjy, she decides to write to ads in a magazine. Cora's husband Tom doesn't seem to like the idea of her writing letters, but he builds her a mailbox bigger than her neighbors.
After the mailbox is complete, they go to the post office to buy stamps and mail their letters. The next day, Cora waits near her mailbox. Benjy tells her its too early and that the mailman hasn't come yet. Cora then realizes that she has never seen a mailman drive by. She opens Mrs. Brabbam's mailbox and finds old opened letters addressed to someone else. Mrs. Brabbam comes and gets her mail. She lies to Cora and says its a letter from her Uncle George.
Days pass and Cora gets no letters. Mrs. Brabbam, however, keeps getting her "mail, smugly waving it at Cora. One day, however, the mailman comes. He says he hasn't been there in years and gives Cora a letter. She waves it to a disappointed and sad Mrs. Brabbam. Cora happily takes it to Benjy, who reads it to her. Cora keeps getting letters as Mrs. Brabbam stays in her house and leave her mailbox open and unused. At the start of autumn, Benjy decides to leave. Cora is sad since he will be going. She is also sad because she still does not know how to write because she spent all her time with him watching him write. As Benjy leaves, he tells Cora he will send letters to her. Cora, sorry for hurting Mrs. Brabbam, asks Benjy for a favor.
Some time later, the mailman comes and leaves mail for both Cora and Mrs. Brabbam. Mrs. Brabbam comes out for the time in months and gets her mail and waves to Cora, smiling. Cora opens her letter from Benjy. It says that he will send her more words every week. On the letter is a picture of a pencil and the word "Pencil" printed out.