Set in the picturesque Magdalen Islands of Québec, Mario is a story of complicity between a strange and solitary ten-year-old boy, Mario, and his older brother, Simon. Withdrawn and living in a surreal world, Mario is completely devoted to Simon, for whom he would dare anything. When a charming interloper captures Simon's affections, albeit temporarily, Mario's love for Simon turns to jealousy and hatred. Eventually the two brothers are reconciled and together they carry out their final attack on reality, one which forces them to confront the ultimate limits of human experience.