In 1940s France, a somewhat disillusioned music teacher arrives at a boarding school for troubled boys. This place, more akin to a prison than a refuge, is filled with difficult youths, rebellious behaviors, and wounded hearts. The new principal, with authoritarian methods, seems more interested in punishing the students than in helping them. However, the protagonist, Clément Mathieu, sees beyond the facade and decides that music could be the key to changing these boys' lives.
Armed with his passion for teaching and a variety of melodies, Mathieu begins to form a choir with the young boys. At first, the idea is met with resistance and mockery, but gradually, the boys become involved, discovering their hidden talents and, above all, the healing power of music. Each rehearsal becomes an opportunity for the students to express themselves, connect with each other, and most importantly, save themselves from the abyss surrounding them.
As the relationship between Mathieu and his students flourishes, he also faces the adversities of a rigidly structured educational system and the harsh reality outside the boarding school. Through this moving story, it is revealed how music can illuminate the path to change and redemption, transforming a group of lost boys into a choir filled with hope and dreams. In the end, the harmony created by them is much more than just music; it is the echo of a second chance for all.