The series follows the adventures of lighthearted Jean-Paul Moulin, a police Commissaire, and his team as they solve crimes.

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?

During the prohibition era, Cornelius, a bootlegger, is on the run from the American coastguards. He comes across a silent film actress, Linda, on the set of a movie and falls in love with her.

Marceau Léonetti, a competent and energetic officer stops by chance the son of an influential lawyer driving under the influence of alcohol. A few months later, the lawyer falsely accuses Léonetti as being violent and incompetent. As a result Marceau is transferred to a small police station, where he meets young and beautiful Jeanne. Soon they are faced with a tough investigation.

A great French restaurant's owner, Monsieur Septime, is thrust into intrigue and crime, when one of his famous guests disappears.

Hector Valentin returns to France from Canada when he inherits a small sawmill. He has difficulties restarting the run-down operation which has inefficient workers and is hampered by the dirty tactics of its bigger...