A quiet painter, separated from his wife for a year, receives a suitcase in the mail from his mother, whom he hasn't seen since infancy. He believes she abandoned him to his wealthy, paternal grandparents. The suitcase contains mementos and a diary, a long letter to him, written over the years, with details of her youth, her first job as a pianist at a cinema, the coming of talkies, her marriage, and how he came to live with his grandparents. As he reads through the materials and her story comes to life, his son Antoine, who's about 10 or 12, tries to break through his father's silence and sorrow by taking matters into his own hands.

In Quebec 40s, orphans or abandoned children are placed in a gigantic psychiatric hospital where children were locked. Were they sick? No, they simply had no family. To escape this oppressive universe, they created a parallel world: the institution's basement where, in a maze of tunnels, they founded an independent company, with its rituals, spells. A young girl, Agnes, reigns over this underground world that adults seem to tolerate.