The film starts in the 13th arrondissement of Paris in 1984. Robert Pinot is a police officer as ordinary as clumsy. One day, he stops a certain Josyane, a young drug addict who is also doubled as a pickpocket, nicknamed Marylou. Having discovered that she comes from the same village, Nanteuil, then him, he takes comion for the young girl and decides to take her under his wing to keep her away from Tony, a dangerous dealer with whom she is in love.