The following version of this book was used to create the guide: Albertalli, Becky. Kate in Waiting. Harper Collins Publishers, 2021.

The novel opens on the last day of Kate Garfield, and her best friend, Andy’s, last day at summer camp. Kate and Andy have a mutual crush on their vocal counselor, Matt, and are saying goodbye. They take a selfie and the scene ends. The next scene opens on the first day of Kate’s senior year. She is mingling with Andy and the theatre kids, who are awaiting the announcement of the school musical. Into the room walks Matt, who informs the best friends that he has moved to town. After discovering that a theatre course called Senior D is open to juniors, Andy signs into the class, but Kate cannot because of a scheduling conflict.

As the action progresses and the school year proceeds, Andy begins a texting relationship with Matt, who is also in Senior D. Although Kate is dismayed, there is a boy named Noah who is showing an interest in her. Unfortunately, Kate is uninterested in him, because Kate was a victim of cyberbullying by the group of boys he belongs to, known as the f-boys. The plot progresses as Kate gets to know Matt better, both because his mother is friends with her mother as well as because she and he are cast as romantic leads in the musical, Once Upon a Mattress. As Kate becomes convinced Matt likes her, due to her closeness to him in the musical, Andy grows closer to Matt in Senior D. Likewise, Noah's feelings for Kate become evident when he asks her for singing lessons.

After an afternoon wherein Kate and Matt rehearse lines at his townhome, Matt confesses he is gay, and the next day, Andy explains to Kate that he and Matt are in a relationship. Kate is furious with Andy, and upon this discovery storms from the room. That weekend, Kate is invited to an f-boy party where she realizes that the f-boys are not as bad as she thought, and Noah makes a pass at her. Kate is angered, because she thinks the pass is just a f-boy move. At the dress rehearsal the following week, Kate realizes she is not offended by Matt’s decision to date Andy, as the reason he is not dating her has to do with his sexuality as opposed to preference. Noah invites Kate to have pizza with him during the rehearsal break, and he confesses he truly has feelings to her, at which time Kate feels attraction.

The next day, Kate devises a scheme to get Andy to take a drive with her to Target during school hours, and Kate apologizes for accusing Andy of betraying her, which he did not. The night of the play, Kate and Matt kiss in the lighting booth. The play is performed, and at the end, Kate’s brother gives her flowers, which makes Kate happy because their relationship, which had been growing distant, is now close again. The next scene shows Kate getting her driver’s license. Upon doing so, Kate feels proud of herself for her newfound independence and for no longer having to take the bus.