Divided into 10 days, the story focuses on the wealthy Van Horns. Orson Welles plays the eccentric tycoon who lives in an Alsatian chateau with his young wife and his adopted son, a sculptor given to hallucinatory fits that cause him to fear he has unknowingly committed murder. Of course, wife and son are having a passionate affair and being blackmailed, which sets in dizzying motion the complex plot.

Inspecteur Lavardin arrives at a cozy, seaside village to investigate the bizarre murder of an eminent Catholic author. The usually cool sleuth is shaken when he discovers that the victim's widow is none other than his old flame.