he has been locked up as a punishment, he finds himself pitying and being attracted to the boy's beleaguered mother and instead tells her that Morhange is at the dentist. Meanwhile, a cruel, uncontrollable boy named Mondain () arrives and begins causing trouble by bullying the others, influencing others to be like him and generally being rebellious. After stealing a watch, he is locked up for two weeks. The choir is improving rapidly with Morhange as its lead soloist; the children are happier, and the faculty less strict — even Rachin begins to loosen up, playing football with the boys and making a paper aeroplane. After Mondain is released from lock-up, he runs away and seemingly steals all the school's money. After Mondain is captured, Rachin repeatedly beats him, until Mondain in turn attempts to strangle Rachin. Rachin hands him over to the police, still not knowing the location of the stolen money, and disbands the choir. Mathieu begins teaching his choir "underground", practising at night in their dormitory. Mathieu continues to meet Morhange's mother, who is unaware of his attraction to her. He plans to help her son win a scholarship to the music conservatory in Lyon. One day she blithely informs him that she has met someone: an engineer. Mathieu is dejected but expresses his feigned happiness and watches her leave in the engineer's car. The Countess, a sponsor of the school, finds out about the choir; they perform before her and others, and Morhange enchants the audience with his solo. Mathieu discovers that another boy, Corbin, stole the money that Mondain was accused of taking. Despite this, Rachin refuses to accept Mondain back at the school. When Rachin departs to accept an award from the board after taking credit for the choir, Mathieu and Maxence suspend classes and take the boys on an outing. While they are out, Mondain returns and sets fire to the school. Mathieu is fired for breaking the rules, even though he saved the boys' lives, and Maxence is suspended. As Mathieu leaves, the boys —forbidden to say goodbye — lock themselves in their classroom, sing and throw farewell messages out of the window on paper planes. Touched, Mathieu walks away, musing about how he has failed and nobody knows of his existence. Back in the present, the adult Morhange finishes reading the diary and recounts what happened afterwards: he won his scholarship