A stranger enters into and forever alters the life of a couple. He claims to be pursued by certain authorities who intend to prevent him from disclosing a secret that only he holds, whence the title. Is he lying, or insane - or is he telling the truth? Who, if anyone, is after him? And what *is* - the secret?
Jean-Louis Trintignant
as David Daguerre
Marlène Jobert
as Julia Vandal
Philippe Noiret
as Thomas Berthelot
Solange Pradel
as Greta
Antoine Saint-John
as Gardien
Michel Delahaye
as Le Médecin
Maurice Vallier
as Bertram
Frédéric Santaya
as Homme oiseaux
Jean-Claude Fal
as Le Forestier
Patrice Melennec
as Gendarme
Pierre Danny
as Chef commando
Jean-François Adam
as Claude Vandal
