Mathieu slowly learns Morhange hides a love of music and a true talent in it. Beyond overcoming the obvious obstacles of Rachin and the students' skepticism and Rachin's egotism, Mathieu has another challenge in newly arrived Pascal Mondain, a truly troubled older boy with pathological tendencies whose presence alone may wreak havoc throughout the school, and not just with Mathieu's project.
Mathieu and Maxence rebel by taking the boys on a paper chase. While they are out, Mondain returns and sets fire to the school with a cigarette. Mathieu is fired for breaking the rules, even though he saved the boys lives, and Maxence is suspended. As Mathieu leaves, the boy, forbidden to say goodbye, lock themselves in their classroom, sing and throw messages out of the window on paper planes. Touched, he walks away, musing about how he has failed and nobody knows of his existence.
Over fifty years later, Morhange and Pépinot, who have not seen each other since that time and who did not spend that much time together while at school, are reading through Mathieu's memoirs from his time at the school, which unmasks the reason why the two are privy to the memoir and the effect he had on their lives.