Roger Corman simply didn't care what he did so long as it resulted in a movie he could sell! Having completed "The Raven" under budget and ahead of schedule, since everybody had already been paid for the next two weeks, he thought he might as well use the available resources to bash out another film in that time ("Dementia 13", the earliest film Francis Ford Coppola will admit he directed because it's not porn, was made in exactly the same way for exactly the same reason, though somehow it's actually quite good).
A very young Jack Nicholson, who had a small part in "The Raven", got to be the male lead, and a very confused Boris Karloff was persuaded to co-star in a production which, as an old-school actor who liked to learn his lines perfectly, he reportedly found genuinely distressing because the scriptwriters were making it up as they went along and he didn't know what his motivation was. And dear old Dick Miller, that irrepressible B-movie character actor who eventually gained minor immortality as the guy who unwisely sold guns to the Terminator (but couldn't provide a phased plasma rifle in the 40-watt range), is the sniveling lackey who sort of ties it all together. A few other people are involved, but their characters make even less sense.
Nicholson's weary soldier, whilst wandering around 19th. century Spain trying to find the Napoleonic War (which must make him the most hopelessly lost character in the history of cinema), blunders into a love-affair with a mysterious girl who looks just like the portrait of angst-ridden nobleman Karloff's long-dead wife, but she won't say who she is, and claims not to remember. This is a film in which every character is deliberately lying, can't remember who they are, or both, apart from the understandably bewildered hero, who knows nothing about anything and doesn't have much luck finding out. The scene near the end where Nicholson grabs Miller and threatens him with extreme violence if he doesn't explain the entire plot right now was shot after everything else. Roger Corman edited the footage he had into some semblance of a story, then told the scriptwriters to write Dick Miller an exposition speech somehow justifying all the foregoing incoherence.
This movie has to be seen to be believed! Corman may have been shamelessly cynical, but his small cast give it everything they've got, especially Karloff, who, despite his advanced age and poor health, is as willing to thrash about in freezing water as Bela Lugosi was in Ed Wood's "Bride Of The Monster". But it's so muddled that it looks as though somebody tried to film one of those long, creepy anxiety nightmares exactly as it happened, with a sort-of-rational explanation tacked on at the end. For connoisseurs of really, really odd movies only. Fun fact: this is the film-within-the-film playing at the drive-in cinema in Peter Bogdanovich's "Targets".
This gothic tale of the supernatural is not one of Roger Corman's cycle of films inspired by Edgar Allan Poe, but it is Poe-adjacent with its necromancy and madness and ghoulish goings-on in the family crypt. While there's a standard plot, the detail is a mess and but for a few lines of dialogue near the climax, it would be impossible to comprehend.
The main reason to watch is the oddity of casting two huge stars at opposite ends of their careers. Boris Karloff plays an elderly aristocrat haunted by visions of his dead wife. And Jack Nicholson is a roving French soldier who wants to get it on with her beautiful ghost (Sandra Knight). It's much more complicated than that, and yet still quite predictable.
Nicholson is annoyingly whiny, but Karloff had been turning out this kind of low budget horror for a lifetime and is clearly in his comfort zone. It's tempting to link his and Corman's relationship with Bela Lugosi's late career association with Ed Wood Jr. Yet although this was squeezed out with zero budget or expectation, it is not so-bad-it's-good trash.
And besides, that's not Karloff in the flood, it's a stand-in, which poor Bela might only have dreamed of. It's poorly edited and the use of multiple directors during its chaotic production is very evident. But there's a classy score... and it still functions as entertainment. Sure, it doesn't get close to delivering on it's title, but it's a miracle films like this even got made.