Belphégor plot
Paris, 1965. A mysterious masked figure haunts the Louvre at night. When a museum guard is found murdered, Police Commissioner Ménardier leads the investigation. Fascinated by the gruesome stories about the phantom in the Louvre, which is now called 'Belphégor', the young journalist André Bellegarde also sets out to investigate. He even lets himself be locked up in the museum at night. André is assisted by Colette Ménardier, the Commissioner's young and feisty daughter. Suspicious is the behavior of the old Lady Hodwin, the alchemist Boris Williams and the attractive but unreachable Laurence Borrell and her twin sister Stephanie. Things get complicated for André when Colette Ménardier and Laurence Borrell turn out to be in love with him.