A bus conductor gets dressed for work in the morning, goes to the toilet, where he is killed by a bomb. The Commissioner and his fat, bumbling assistant, Inspector Charbonnier are put on the case. After interviewing friends, wives, colleagues, and spying on strangers who might be connected, our heroes trace the assassin down to a mental institution where, it seems, the murder victim has been an inmate for the last three years...
L'inspecteur Charbonnier
Le commissaire Pichard
Gazul
Gwendoline
René
Barbocelli
Joseph Ordure
La mère du médecin
L'entraîneur
Odette Jeandrin
Le psychiatre
Mme Piazzorossicelli
Le majordome
Le boxeur
Angelo
Rose
Le joueur d'orgue de barbarie
Le concierge
un inspecteur (non crédité)