Jean -Louis catches vipers he sells to the laboratories.A trivial incident causes his descent into hell: he forgets to use the pedestrian crossing and the policeman is cross.Who could have believed then where it would lead the unfortunate Jean-Louis to?Two unscrupulous journalists depict him as a monster ,who releases vipers in town.Because of a hold up,the city is looking for a scapegoat ,and this poor lad looks the part too much. Although the superintendent insists there's really nothing against him ,Jean-Louis becomes paranoiac and hides in shady places .He leaves his girlfriend ,meets a hooker and a shifty aging man .