At an Idaho IGA store, Amber Lange, a pregnant woman, encounters an old classmate and learns about the recent death of Thayer Mangeres, a former schoolmate who tragically jumped into a river. This revelation prompts Amber to reflect on her high school days, where she was an unhappy yet popular cheerleader and had strained interactions with Thayer, who was known as the “problem kid.” Due to their last names, they often found themselves seated next to each other in class. In a particularly shocking moment during science class, Thayer attempts to impress his peers by drinking blood from a dead fetal pig, which leaves Amber more disgusted than impressed, leading her to dismiss him outright. This rejection sets off a chain of events where Thayer begins to torment Amber throughout their shared classes.
As the story unfolds, a new student named Tabitha arrives and quickly bonds with Thayer, allowing them to together mock Amber. Frustrated with the bullying, Amber reports Thayer's behavior to their teacher, resulting in a visit to the principal. Upon returning home, Thayer faces his own horrific struggles as his father punishes him harshly for his actions, with his brother Dooley holding him down.
Despite the bullying, Thayer begins to express his inner turmoil through poetry in Creative Writing class. Amber, who is also grappling with a loveless home life due to her parents’ frequent absences, detects the silent pain in Thayer's poems. In a subtle act of compassion, she shares an orange with him during Study Hall, leading to the development of a private friendship between them. Through their poetry recitals, they begin to exchange deep emotions, drawing closer to one another in the process.
As challenges stack up, Amber continues to contend with feelings of social pressure, abandonment, and rejection, while Thayer's issues deepen as he struggles to protect his older sister Jeannie from abuse at home. They share their secrets in a notebook during their study sessions, seeking solace in one another. However, things take a dark turn when Thayer witnesses Amber being intimate with another boy at a party, leaving him feeling betrayed. In retaliation, he reads a hurtful poem about her in class, further escalating their tensions.
Seeking revenge, Amber retrieves the shared notebook and lets Tabitha read it, humiliating Thayer as his private thoughts get circulated around school. The aftermath grows dire when, in class, Thayer takes pills in front of Amber as an act of desperation, resulting in an overdose and a severe seizure. After this incident, Thayer disappears from school, allowing Amber’s life to revert to its previous state.
A year later, their paths unexpectedly cross again while Amber is shopping; she nearly fails to recognize Thayer, who now works as a Mormon missionary. Their next encounter at the beach sees Amber inquiring about his mission, only to learn that he returned home early. In a poignant moment, as Amber mentions her upcoming marriage, Thayer abruptly shifts the conversation to hypothetical notions of faking his death, prompting Amber to assert that she would know he was alive.
As the story reaches the present, Amber learns that Thayer's family has suffered tragic losses, sparking her curiosity about whether he may have truly faked his own death. Determined to uncover the truth, she visits Thayer's old home and finds Jeannie living there alone. Coming to terms with the uncertainty surrounding Thayer's fate, she takes a trip to their old high school, returning to her seat in Study Hall—where they once shared joyful moments. There, she retrieves the old notebook that she has cherished over the years, writing a heartfelt passage and passing it to Thayer's old desk. Later, a touching scene unfolds as Jeannie stands at the doorway of a hospital room, her eyes filled with tears of joy as she observes Amber cradling her newborn son, whom she has named Thayer.
