What an utter mess of a film.
I have watched enough Franco to know what I am getting into when I hit play on one of his movies, but this one is a new low.
The movie is dead slow. Not even 90 minutes and it feels like twice that length.
There is no story, and close to no dialog. Were it not for the synopsis, one would have no clue what is going on here. I really think Jess just wanted to have Doctor Frankenstein, Count Dracula, and a werewolf in a movie. Mission accomplished, but it is terrible.
Let's try to breakdown the story: Doctor Frankenstein has taken control of Count Dracula. How does he do that, you ask. Electricity. Is that not a sufficient answer? Too bad! Okay, why is he doing this? Surely Frankenstein has a clear plan for what he is doing. Nope. He's doing this for reasons, it's not important.
As I already mentioned, a werewolf shows up at the end. He may be the worst werewolf in the history of cinema. Just looks like they rubbed some brown paint on someone's face and called it a day. Now why would a werewolf just show up? Unclear. How would he know to get involved? What is he expected to do, since he doesn't have a wooden stake or sunlight at his disposal? None is this is addressed, then the movie just ends.
Probably the worst Franco movie I have seen, and one of the worst films I have watched, in general.

Post script: As if all of this wasn't bad enough, the movie makes use of real bats. One example looked as if people took a bat and held his wings apart, then shook him, to give the illusion of flight. Why? The movie also uses shitty fake bats on strings, so why not just use fake bats the entire time?
The other example, and definitely the worst, a bat is shown inside a glass container and fake blood is poured in, to the point where the little guy is fighting for his life. Really?! You're going to drown a bat for this piece of shit movie! Now, the scene does cut while the bat is still moving, so I'd like to think he got out alive. However, this is the same guy who made a movie - _Bloody Moon_ (1981) - where a snake's head was cut off.
So, yeah, fuck you, Jess Franco! I'm glad you're dead.