A serial killer murders women by knocking them out with the handset of a phone and signs his crime by sticking the dial in his victims' forehead. Private eye Marc Elbichon (whose real name is Marcel Bichon), craving for notoriety, sets about tracking down the killer. To support him, Marc calls on two childhood friends : Franck Potin, the owner of a bar without patrons and Blacky, a radio presenter. He also requires the help of Momo, his assistant and 'cleaning man' and of Ugo, a reporter already on the trail of the killer.