St. Val's Mystery (original: French: Le Mystère de Saint-Val) is a 1945 French comedy film starring Fernandel directed by René Le Hénaff,[2][3][4] Shot during the winter of 1944–1945 in the Boulogne Studios, this was the Fernandel's first film following the liberation of Paris.

It was then released in Denmark on 23 October 1950 as Det mystiske slot and in Portugal on 1 June 1954 as Fernandel, Polícia Amador.

An insurance-office clerk Désiré Le Sec (Fernandel) dreams of being a great detective.

The clerk's uncle (Marcel Carpentier) is his boss at that agency, and sends Désiré out on a frivolous mission to Saint-Val Castle, where the master of places has been found dead through mysterious circumstances.

[4] Summarizing, Travers felt the gags were predictable, the plot "hackneyed and pedestrian", and the "unimaginative pay-off definitely does not reward" the viewer.,[4] concluding that this marked the film as "clearly not Fernandel's finest hour".