Dr. Cordelier, living in a suburb of Paris, withdraws from society to pursue research into the functioning of the human brain. His lifelong friend, Maître Joly, becomes concerned when Cordelier draws up a will that bequeaths his entire estate to a stranger, Monsieur Opale; he cannot understand why Cordelier defends him, considering Opale attacks women and children. After a colleague is killed, Joly confronts Cordelier and discovers the truth behind his friend's behavior.
Jean-Louis Barrault
as Dr. Cordelier / Opale
Teddy Bilis
as Maitre Joly
Michel Vitold
as Dr. Lucien Severin
Sylviane Margollé
as Little girl attacked by Opale
Jacques Danoville
as Commissioner Lardaut
André Certes
as Inspector Salbris
Jean-Pierre Granval
as Boss of the short-time hotel
Jean Bertho
as First passer-by during the aggression
Jacques Ciron
as Second passer-by during the aggression
Annick Allières
as Neighbor
Dominique Dangon
as Little girl's mother
Jean Topart
as Désiré, butler
