The book opens to a lunchroom. Aza, Daisy, and Mychal are having a conversation. This is where the also are introduced to Aza, (the main character), and the mental illness she has. We're left wandering through her thoughts as she's worried about the bacterial disease: C diff. While distracted from the conversation, Daisy proceeds to tell Mychal that Mr. Russel Pickett has gone missing, and there's a $100,000 reward to anyone with information about the disappearance.
Daisy reminds Asa that she knows Mr. Pickett's son, Davis. So they decide to travel down the White River to see if they can retrieve camera footage from the Pickett residence to see if they can find Mr. Pickett. In the midst of doing so, Lyle, the security guard, catches the girls in action. Daisy lies to him and says the canoe has a hole in it, and Lyle takes them to see Davis.
Davis, Aza, Daisy, and Mychal all go back to Davis' house after a double date. Davis takes Aza outside on his golf course and they begin talking, both completely unaware of the others' affection for them. Mr. Pickett is brought up and how Davis doesn't trust Aza and Daisy to stay quiet about it. So he takes her to a cottage on his property and pulls $100,000 out of a cereal box and gives it to Aza to earn their trust. Her and Daisy freak out and Daisy has thoughts of spending all of it.
Davis and Aza begin unofficially dating. A while later, Aza's mental illness begins to take a toll on her life. She believes she has C. Diff in her stomach, and her therapist isn't helping her through it. She decides to drive with Daisy to Applebee's, where Daisy tells her how exhausting and a bad friend Aza is. This distraction leads Aza to rear-end a car, and two other cars collide with her. Putting Aza in the hospital for her injuries.
Aza returns to school in December. Following her first day back, Daisy and Mychal invite her to go to an art show in the sewer. Daisy and Aza go off walking alone soon to realize they're in the "jogger's mouth", and the stench within it is almost unbearable. Which is symbolic to Mr. Pickett. Aza returns home and tells her mom that she's worried she found Mr. Pickett's down in the sewers. Aza tells Davis the following day and he begins to cry. After he leaves, he doesn't text Aza anymore.
Some months pass, and Aza still hasn't heard anything from Davis. Aza hears on the news that the police discovered Mr. Pickett's body in the Porgue Run sewer. She informs Davis who then tells her he and his brother told the police about their dad. During April, Davis goes to Aza's door to tell her that he's moving to Colorado and even brings her a gift: a painting. Their relationship ends. Aza takes advice from her psychiatrist and writes about herself years on in the future. Writing helps her to overcome her worries and learn to be herself as a single individual.