The following version of this book was used to create this study guide: Silver, Josie. One Day in December. Broadway Books, 2018. Paperback Version

As the narrative begins, it is Christmas time. Laurie is riding a bus on her way home from working at a hotel that she hates. She dreams of being a writer. Laurie is not enjoying the bus ride. Even worse, she does not look forward to going home to an empty apartment. Sarah, Laurie's roommate and best friend, has already left for the holidays. Laurie is looking forward to spending Christmas at her parents' home. She is thinking of this and all of the germs she is catching on the bus when it stops. She looks out of the window. Instantly, she falls in love with a man she sees at the bus stop. He also sees her. Even though she feels a connection between the two of them, she does nothing to try to make contact with him. He makes a move to get on the bus, but it is too late. The bus drives away from the stop.

When Sarah returns after the holidays, Laurie tells her about the man. They decide to call him "bus boy." Laurie and Sarah have a friendship so close that they actually view each other as sisters. The two of them try to find the bus boy, but they are unsuccessful. That changes when Sarah invites her new boyfriend, Jack, to a party. It turns out that Jack is bus boy. Laurie recognizes him, but she does not say anything because of her relationship with Sarah. Jack also recognizes Laurie, but he hopes that she does not recognize him.

Time goes on and an unknowing Sarah orchestrates activities that bring Laurie and Jack together. Sarah wants the three of them to be friends. Laurie tries to keep her distance. Then, one evening she tells Jack about the childhood death of her sister, Ginny. Afterward, she realizes that she crossed a line. She crosses another line when she is depressed after her father’s heart attack. This time she kisses Jack. Later, she tells Jack to forget the kiss, but it is too late. He knows that she knows he is bus boy. He also has feelings for her. His relationship with Sarah is not the same after his kiss with Laurie, even though he and Sarah stay together.

In the meantime, the two girls move from their apartment. Laurie takes a trip to Thailand. While there, she meets a man named Oscar. They spend time together and continue to date when they return to England. Sarah and Jack meet him and while Oscar and Sarah get along with each other, Jack does not like him and does not hide his dislike. One night, when he is supposed to join them for dinner, but is waiting until the last minute to arrive, he has a car accident. The timing is bad because he is a DJ and has just resigned from his current job because he has a new one, in theory. He loses the opportunity after his accident because he has problems hearing out of one ear. The accident makes Jack unpleasant to be around. He insults both Sarah and Laurie. Still, Laurie sees him as her dream man.

Jack recovers. The accident causes Sarah to meet her future husband, Luke, because it is Luke who finds Jack and phones Sarah. Ultimately, Sarah breaks up with Jack because he is not one hundred percent of her dream guy. He only thinks of himself. Just as she does this, Oscar asks Laurie to marry him, and Laurie accepts.

More time passes. Jack moves to Edinburgh, Sarah moves to Australia with Luke. Laurie divorces Oscar because she does not want to follow him when he gets a promotion. One evening Laurie is listening to Jack’s radio program. She decides to call using a pseudonym. As she tells her story, she says that she loves the man she saw on the bus; but, she never told him. Jack knows that it is Laurie and advises her to tell the man how she feels. Listeners realize that Jack knows the person. Laurie, who is the mystery woman, becomes a social media sensation because everyone wants to know who the mystery woman's name. Sarah knows and sends her a one way train ticket to Edinburgh. When Laurie gets there, Laurie knows vaguely where to go. When she gets to the radio station, the taxi driver, who knows who she is by now, advises of about what to do. As Laurie and Jack profess their love for each other, Laurie feel complete.