In Saint-Rupert, Basse Lozère, the son of a family of garbage collectors, Pissenlit, who has played the mentally deficient since childhood so as not to be forced to go to school, is in fact a prodigy in mathematics: by reading a book found in a trash can, he revolutionizes a mathematical theory. Meanwhile, his father is making a computer from objects recovered from garbage cans, and capable of composing musical "hits" that may make him a star.