Louis Bertain is the owner of a Paris garage which is the front for a robbery gang. He and his accomplices are careful to keep up a civic veneer by day, indulging in criminal activities only when "the red light is on" at night. This status quo is upset when one of the gang members becomes convinced that Louis' younger brother is a police informer.

Jean Gabin
as Louis Bertain/Louis le blond

Paul Frankeur
as Fredo

Marcel Bozzuffi
as Pierre

Lino Ventura
as Pepito

Annie Girardot
as Hélène

Albert Dinan
as l'inspecteur Pluvier

Antonin Berval
as Zé

Thomy Bourdelle
as Un inspecteur

Serge Lecointe
as Bébert

Jean-Pierre Mocky
as Pierre