It's hard to explain the appeal of this movie. It's not a gem as some have said. But I wouldn't characterize it as Euro-trash either. The plot is not very original, and relies on standard haunted house conventions, perhaps pirating some from Robert Wise's THE HAUNTING (1963). It may also have a literary source in Bulwer-Lytton's story "The Haunters and the Haunted," which also tells the story of a disbelieving rationalist who wagers he can spend a night in a mysterious house where spirits relive incidents from past lives. The film is full of continuity holes (or should I say "challenges"), because many may be explained away. But the execution is flawed. Feral cats, sudden scenes of carnage, and other fright effects do not deliver the shudders.
I must say, however, that the film held my interest, primarily because of the creepy, fog-shrouded sets that look better than they ought to on such a small budget, and because the performances are above average for this type of fare. And although the plot is full of old dark house clichés—slamming doors, billowing curtains, and mysterious portraits—some nice dialog makes it all seem less contrived somehow. There is no doubt that the director and writers were absolutely sincere.
There is also some provocative sexual content and nudity following a tradition of salaciousness that seems to have been a necessary ingredient of horror films as far back as Hollywood's pre-code days. So if I were forced to assess whether this glass is half empty or full I would say it is slightly more than half full. This one might appeal to all those baby boomers who watched the soap opera DARK SHADOWS when they were teenagers in the '60's. It has that feel to it, only with better acting and writing.