Young artist Monte Crandell is being sued for an unauthorized caricature. To escape arrest, he disguises himself as a mystic, only to conjure up a genuine ghost during a seance. Things come to a head during his trial, where the invisible ghost takes the witness stand on Our Hero's behalf.

A London curator loses the Mona Lisa to a collector, who discovers it's a fake.

Inspector Cassin, a renowned Paris detective, departs to the country for a much-needed break. There he falls in love with the innkeeper’s daughter, Nanette, who is already betrothed to a local farmer. On the evening of their engagement party, Nanette and the farmer both disappear. Cassin takes up the case immediately to discover what happened to them and who is responsible.