Lara Jean Covey, a high school student, writes letters to boys she likes and keeps them in her closet. Her latest letter is to her childhood friend Josh, who is dating her older sister, Margot. When Margot moves out for college, she breaks up with him, but Lara Jean, who has always had a crush on him, doesn't dare say anything to him. What she doesn't know is that her own letters will eventually do it for her.