The musical has its origins in an incident that took place during Pasek's high school years. The musical "takes the notion of a teenager, ... Evan Hansen, who invents an important role for himself in a tragedy that he did not earn."
High school student Connor dies by suicide. Connor's parents, Cynthia and Larry, find a note apparently from Connor to Evan Hansen, a senior at the same high school. The note actually was written by Evan himself in an exercise suggested by his therapist to help Evan overcome his socially awkward personality and anxiety. Evan's mother Heidi works long hours as a nurse and also attends school, and his father left the family years ago. Although the two young men did not know each other, Evan decides to attempt to help Connor's parents in their grief by pretending to have been a close friend of his and writing fake e-mails to reinforce his claim. Zoe, Connor's sister, and Evan's "dream girl", is grateful to Evan for helping her parents.
According to the official website, the synopsis reads "All his life Evan Hansen has felt invisible. To his peers, to the girl he loves, sometimes even to his own mother. But that was before he wrote the letter – that led to the incident – that started the lie – that ignited a movement – that inspired a community – and changed Evan's status from the ultimate outsider into the somebody everyone wants to know. But how long can Evan keep his secret? And at what price?"