An American grandson of the infamous scientist, struggling to prove that his grandfather was not as insane as people believe, is invited to Transylvania, where he discovers the process that reanimates a dead body.
 
No review.  Just a quote from the movie.
 
Inga: Werewolf!
Dr. Frederick Frankenstein: Werewolf?
Igor: There.
Dr. Frederick Frankenstein: What?
Igor: There, wolf. There, castle.
Dr. Frederick Frankenstein: Why are you talking that way?
Igor: I thought you wanted to.
Dr. Frederick Frankenstein: No, I don't want to.
Igor: [shrugs] Suit yourself. I'm easy.
 
Nuff said.
 
FUN FACT:  When Mel Brooks was preparing for this film, he discovered that Ken Strickfaden, who'd made the elaborate electrical machinery for the lab sequences in the Universal Frankenstein films, was still alive and living in the Los Angeles area. Brooks visited Strickfaden, and found that he had stored all the equipment in his garage. Brooks made a deal to rent the equipment, and gave Strickfaden the screen credit he didn't receive for the original films.