Inspired by true events, mild-mannered and responsible family-man Jacob Mann returns to his hometown of St. Louis to be inducted into his High School Hall of Fame. Unbeknownst to his family and childhood friends, Jacob is secretly using this trip as a way to confront and finally beat up his high school bully, Nate Tagliabu.

Set against the weight of a single shared birthday, Eighteen follows five young men, Fletcher, Waylon, Ben, Wes, and Caleb, each crossing the threshold of adulthood in their own way, on the same day.