A phantom appears in the Louvre museum in the middle of the night in search of something in the dark corridors.

A ghost haunts the famous Louvre museum. One night, he knocks out an attendant near the statue of Belphégor. A journalist, Bellegarde, investigates, in spite of his infuriating mistress, Simone Desroches. When his investigation runs into difficulties, he is helped by Detective Chantecoq, who succeeds in unmasking Belphégor, and is stunned to discover who it is.—dbdumonteil