Kate is one of two protagonists in this story, which follows the lives of her and her best friend as they grow from teenagers to adults. At the start of the novel, Kate is a shy and awkward eighth grader who keeps her head down and immerses herself in books. Kate’s life is turned upside down with the arrival of Tully Hart, her new neighbor and the coolest girl Kate has ever seen. After they become fast friends and confidantes, Kate starts to come out of her shell. However, Kate continues to live vicariously through Tully for the remainder of high school and into college. Even after Kate meets Johnny and falls in love with him, she recedes into Tully’s shadow. After realizing that Johnny has feelings for Tully, Kate lacks the confidence to tell anyone how she really feels about him, a mistake that leads to a one-night stand between Johnny and Tully and Kate’s decades-long feeling that she was his second choice. For most of her life, Kate cannot shake this belief, which feeds her jealousy of Tully and her own insecurities.

After Kate and Johnny get together, get married, and have children, Kate dedicates her time to her family.