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 compassion 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.

Gardien de la paix sympathique et maladroit, le brigadier Pinot décide de prendre sous son aile Marylou, une jeune toxicomane originaire du même village que lui. Mais la jeune femme est sous l'emprise de Tony, un dangereux dealer. Le policier va prendre tous les risques dans cette affaire qui pourrait lui coûter sa carrière... ou faire de lui un héros.