This obscure film from an even more obscure production company is an obvious attempt to cash in on Roger Corman's hugely successful Edgar Allan Poe movies, all but one of which starred Vincent Price (and the only reason he wasn't in "The Premature Burial" was that Corman was churning them out so quickly that Vincent was accidentally double-booked). Based on the writings of Guy De Maupassant, primarily his classic short story "The Horla", this film finds Vinnie in very familiar territory, playing a charming, well-meaning, and smugly complacent 19th century authority figure who soon starts to go dangerously nuts for incredibly strange reasons.
Unfortunately, the production values are very poor. The almost totally invisible monster is clumsily portrayed, the fact that Paris consists entirely of tiny indoor sets is often painfully apparent, and both the script and the supporting actors are so busy woodenly retreading slightly out-of-date horror movie tropes that sometimes you could be watching absolutely any film from this era. Worst of all, the direction is very flat, giving Vincent Price too few opportunities to go over the top in the way he really should in a film like this, and submerging the few moments of horror in far too much predictable costume drama.
If half stars were allowed, I'd put this film precisely on the borderline between good and bad, but I'll give it three stars because anything starring Vincent Price gets the benefit of the doubt, even if he's not at his best. It's a great story that would have suited him down to the ground if it had been handled better, but unfortunately the whole issue of whether or not the totally implausible invisible being that drives him to kill might perhaps be a figment of his imagination is pretty much forgotten about, and a lot of potential is wasted. Still, Vincent Price is always worth a look, even if he's not at his best, so in all fairness I have to say this deserves an honourable mention, but it's nothing to write home about.