In 1940s Quebec, a group of orphaned children are placed in a mental asylum. Byproducts of a broken social system, the children -- who are of sound body and mind -- create a secret society in the underground passages below the hospital, selecting plucky young Agnes Laberge (Charlotte Laurier) as their leader. The orphans' safe haven from the adult world comes under threat when a sick child goes missing, and the hospital suspects the children are to blame.