After each interview, Walt rethinks what he said to the students and slowly draws out old, painful memories of his high school years, in spite of his intention to avoid these thoughts. Ultimately, the students complete the project and cease coming to Walt's house. Two years after their graduation, however, they return to their social science teacher's classroom and tell her of their activities. The students are excitedly planning to see Walt and are disappointed when they couldn't talk with him.
Later, the teacher, a long-time friend of Walt's wife, is visited by Walt's surprising confidant who shares with her Walt's story if what happened that day on the northern prairie that left a man dead and how Walt was running from that event all his life.
Montana in The Rearview Mirror has a touch of the 'murder mystery' but is mainly a retrospective coming of age story as remembered by an 81-year-old man talking with high school seniors in 2020. He tries to keep his memories on 'the good stuff' but cannot discipline the 'bad stuff' to keep it out of his mind. Those memories lead him back to the bottle and the return of his angst that he will be caught and punished for an ancient sin.